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LL 14: Roofs and Attics

AIVC, 2001
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Bibliographic info: LL 14
Languages: English

Roofs and Attics


#NO 11545 Wind-driven ventilation in courtyard and atrium buildings in urban areas. 

Sharples S, Bensalem R

UK, Air Infiltration and Ventilation Centre, proceedings of "Ventilation Technologies in Urban Areas", 19th Annual Conference, held Oslo, Norway, 28-30 September 1998, pp 118-126.

A wind tunnel study was carried out to investigate the airflow through courtyard and atrium building models. Ventilation strategies resulting from the use of different atrium roof pressure regimes (positive pressure and suction) were examined and compared with the performance of the open courtyard. The model buildings were monitored both in isolation and in idealised urban environments of varying group layout densities. The effect of wind direction was also observed. The results from the study suggest that the open courtyard in an urban environment had a poor ventilation performance whilst an atrium roof with many openings under a negative (suction) pressure regime was the most effective. Changing the wind direction from perpendicular to the building facades to a 450 incidence angle had the effect of making the differences in the observed flows between all the models much smaller.

wind effects, wind tunnel test

#NO 11548 Experiences from wall exhaust systems in blocks of flats.

Palonen J

UK, Air Infiltration and Ventilation Centre, proceedings of "Ventilation Technologies in Urban Areas", 19th Annual Conference, held Oslo, Norway, 28-30 September 1998, pp 145-153.

A self administrated questionnaire was mailed to over 300 dwellings in blocks of flats using the wall exhaust. In almost all the dwellings there was a controllable ventilation unit. The units were either a mechanical exhaust ventilation system type with outdoor air inlets or mechanical supply and exhaust ventilation system with heat recovery and outdoor air intake on the wall. In the questionnaire, the daily use of ventilation unit, noise levels as well as odors and their sources in the dwellings were asked. The prevalence of odors in the dwellings using wall exhaust was in the same level as in dwellings with traditional way to conduct exhaust air from dwellings to roof reported in earlier studies. Habitants in the dwellings with mechanical supply and exhaust ventilation system reported less draught, slightly less odor problems and judged the air quality more fresh even in the bedrooms in the mornings than habitants in dwellings with mechanical exhaust ventilation system only. Habitants in dwellings with mechanical supply and exhaust ventilation system were much more satisfied with the ventilation system and they regarded their dwellings more comfortable than habitants in dwellings with mechanical exhaust ventilation only.

apartment building, survey

#NO 11560 Airtightness of timber frame buildings without a plastic film vapour barrier.

Sikander E, Olsson-Jonsson A

UK, Air Infiltration and Ventilation Centre, proceedings of "Ventilation Technologies in Urban Areas", 19th Annual Conference, held Oslo, Norway, 28-30 September 1998, pp 261-269.

Good airtightness of a building can be achieved by the incorporation of an inner sealing layer for the exterior walls and roofs in the form of a plastic film, which also serves as a vapour barrier. However, if it is not wished to use plastic film as an inner sealing layer, then airtightness must be effected through the use of other materials or in some other way. The project has been concerned with investigation of a number of alternatives. It has been found that the arrangement most commonly used in Sweden today comprises polymer-based fibre sheets (which permit diffusion) and gypsum board, as alternatives to plastic film on the inside of the structure. The work of the project has shown that, provided that the materials are airtight in their own right, it is possible to achieve as good airtightness with alternative materials as can be achieved with plastic film. This has been demonstrated in the laboratory and in three of five houses in the field investigation. However, the airtightness performance of the finished building can be very poor unless care is taken both in the design and in construction, and this was also revealed in the field work.

air barrier, workmanship

#NO 11579 Modern passive stack and ventilated schools - evaluation of ventilation and moisture conditions.

Blomsterberg A, Sikander E, Ruud S

UK, Air Infiltration and Ventilation Centre, proceedings of "Ventilation Technologies in Urban Areas", 19th Annual Conference, held Oslo, Norway, 28-30 September 1998, pp 450-457.

The aim has been to determine ventilation rates and risk of moisture damage in three modern schools with passive stack ventilation. The users are supposed to control the ventilation by using the lantern windows and the outdoor air is assumed to enter through an underground duct. The paper presents results, analysis and conclusions from the performed measurements and calculations. The ventilation rates are sometimes low and vary with the use of the windows in the facade and the lantern. It is, however, always possible to arrive at a sufficient ventilation rate. The supply air flow through the underground duct can, without a supply fan, be low and even go backwards during warm weather. To obtain desired ventilation rates and energy conservation the building must have a good airtightness. High relative humidities and even periods with condensation occur in the underground supply duct during spring and summer. Microbial growth has been found in two of the schools. Two important factors are choice of material and cleaning, where the knowledge is insufficient today. Moisture and microbial growth have been found in the roofs. The leakage paths, supply of moisture indoors and an interior pressurisation have contributed. In order to reduce the risks the building must have a good level of airtightness.

humidity, occupant control

#NO 11580 A wind tunnel study into the location of natural ventilation air intakes in urban areas.

Green N E, Etheridge D W

UK, Air Infiltration and Ventilation Centre, proceedings of "Ventilation Technologies in Urban Areas", 19th Annual Conference, held Oslo, Norway, 28-30 September 1998, pp 458-466.

Ventilation of buildings in urban areas may result in high internal concentrations of traffic pollutants if air intakes are positioned where external concentrations are highest. This paper presents the results of a wind tunnel study into different wind-driven natural ventilation strategies for a building situated close to a busy road. Measurements of the concentration of a simulated traffic pollutant inside and around the building illustrate that noticeable reductions in internal concentrations can be achieved if air intakes are placed at roof level or on the leeward face of the building.

air intake positioning, traffic pollution, wind effects

#NO 11627 Comparison between computed and field measured thermal parameters in an atrium building.

Laouadi A, Atif M R

UK, Building and Environment, No 34, 1991, pp 129-138, 9 figs, 1 tab, 16 refs.

This paper presents a comparison study between simulation and field measurements of thermal parameters of an atrium building in Ottawa, Canada. The selected atrium was an enclosed three-storey building with a pyramidal skylight. The atrium was fully conditioned and has open corridors at each storey connecting it to adjacent spaces. The atrium space was used for circulation and reception while adjacent spaces are offices and meeting rooms. The atrium was monitored in June 1995 and in December 1995 to consider extreme conditions of the outdoor climate. The simulation results were obtained using ESP-r computer program. The comparison included those of predicted and measured solar radiation entering the atrium space at the rooftop, and predicted and measured indoor temperatures of the atrium floors. Results for the solar radiation showed good agreement between the measured and predicted values. When the mechanical system was turned off, the predicted temperatures were within +/- 2oC of the measured temperatures in winter. In summer, however, the predicted temperatures were 2-3oC higher than the measured temperatures.

thermal comfort, atrium

#NO 11637 No heating at all? Is it possible in a Swedish climate?

Anon

Sweden, Swedish Building Research, 3/98, pp 2-6.

Describes houses in Gothenburg, Malmo and Hannover which are so energy efficient that they need no special system for heating . The terraced two-storey plus attic houses are currently under construction. They are very airtight and have very thick insulation with highly insulating windows and energy efficient electrical appliances and lighting. The technology is not new, but is applied with great attention to detail. The project forms part of an EU project "Cost Effective Passive Housing for European Standards (CEPHEUS)" supported by the EU Thermie programme. They utilise passive solar heating and very thick insulation. Leakage of heat is limited by an airtight layer. The requirement is 0.5 ach at a negative pressure of 50 Pa, with 0.2 ach when unoccupied.

heating, terraced house, zero energy house

#NO 11650 Lufttathet i hus med traregelstomme och utan plastfolie. Airtightness of buildings with a timber frame and without plastic foil vapour barrier.

Sikander E, Olsson-Jonsson A

Sweden, Swedish National Testing and Research Institute, SP Report 1997:34, 85pp, in Swedish.

Good airtightness of a building can be achieved by the incorporation of an inner sealing layer for the exterior walls and roofs in the form of a plastic film, which also serves as a vapour barrier. However, if it is not wished to used plastic film as an inner sealing layer, then airtightness must be effected through the use of other materials or in some other way. This project has been concerned with investigation of a number of alternatives. It has been found that the arrangement most commonly used in Sweden today comprises polymer-based fibre sheets (which permit diffusion) and gypsum board, as alternatives to plastic film on the inside of the structure.

The work of the project has shown that, provided that the materials are airtight in their own right, it is possible to achieve as good airtightness with alternative materials as can be achieved with plastic film. This has been demonstrated in the laboratory and in three of five houses in the field investigation. However, the airtightness performance of the finished building can be very poor unless care is taken both in the design and in construction, and this was also revealed in the field work.

airtightness, vapour barrier

#NO 11655 Daylighting in buildings.

McNicholl A, Lewis O (eds.)

Ireland, University College Dublin, School of Architecture, Energy Research Group, for the European Commission Directorate General for Energy (DGXVII), UCD-OPET, A THERMIE Programme Action, 1994, 24 pp.

Covers daylight and energy, daylighting data, costs, elements of design: roof lights, atria, glazing, transparent insulation, light shelves and reflectors, light pipes and light ducts, shading, artificial lighting, integrated controls; retrofit, design tools, case studies.

daylighting

#NO 11685 Natural ventilation and automation with manual overriding are health solution.

van Paassen A H C, Lute P J

TVVL-REHVA Symposium: Healthy Buildings in Relation to Building Services, 17-21 February 1992, Utrecht, The Netherlands, pp 79-92, 8 figs, 1 tab, refs.

The need for individual control with manual overriding combined with controlled natural ventilation is discussed. It is made plausible that with these two facilities problems related with the Sick Building Syndrome can be avoided.

This principle is applied in a so-called passive climate system. A system is devised setting the level of heating and ventilation by controlling motors fitted to radiators, ventilation openings in window, Venetian blinds and outside shading. Moreover, it will switch on the lighting when natural lighting is inadequate. The system comprises a weather station on the roof, a network of sensors and controllers in each room hooked up to a control computer. The room controllers can be overridden manually by the occupants.

With computer simulations it has been demonstrated that through nocturnal air cooling with opened windows and predictive control a comfortable indoor climate can be realised year round, provided that the internal load lies between 15 and 20 W/m2. Higher loads require additional mechanical cooling. Moreover, it is shown that a proper combination of controlled natural ventilation and mechanical cooling leads to an enormous reduction in energy consumption. It can be reduced to 20% of the amount that is normally required in buildings with closed facades. Moreover, the capacity of the cooling room unit can be reduced with 50%. The ability to remove internal heat and the costs of the passive climate system is compared with that of more conventional systems. It has been shown that the passive system is very promising and that the option with the additional cooling unit is superior to all the other systems.

occupant control

#NO 11705 Biological contamination forces school evacuation: Part 2.

Anon

USA, IEQ Strategies, August 1998, pp 8-11.

More than 400 students and 30 staff members had to be evacuated from a midwestern US elementary school for nearly five months as a result of health complaints from old mildew and chemical exposure. The thrust of the recommendations was to control water infiltration into the building, clean up biological contamination in all areas from the service tunnels to the roof deck, seal penetrations from the service tunnels into the classrooms, clean and repair the unit ventilators, remove any confounding asbestos insulation (and repair remaining materials), reinsulate steam lines, and subject the facility to an intense cleaning and disinfection to remove any residual fungal spores. Post-remediation testing to verify air quality prior to the readmission of occupants would follow these repairs and cleaning. A thorough cleaning process and sorting and discarding of many teaching materials caused some distress to teaching staff.

biological pollutant, school

#NO 11714 Crawl space: how to avoid moisture and soil gas problems.

CMHC

Canada Mortgage and Housing Corporation, 1998, 9 pp.

Crawl spaces often do not get adequate inspections and there is a general lack of appreciation by the housing industry for the elements that make up a effective moisture control strategy. Moisture related problems occur in many crawl spaces despite the fact that building codes require vents. Moisture from the crawl space can move into the living area or even into the attic, causing mould growth problems. Houses with high levels of air leakiness will move crawl space air into the house regardless of the type of heating system. Many problems found in crawl spaces are related to a misunderstanding of how crawl spaces work. The insulation, air and vapour barriers are typically not well integrated with the rest of the house. Many crawl spaces are built over an exposed dirt floor, rather than incorporating a ground cover, floor drain and perimeter drainage similar to a properly constructed basement. Recent research has illustrated alternative crawl space construction techniques. Passive ventilation may often be unnecessary or ineffective. The purpose of this publication is to explain the latest understanding of crawl spaces, and how they should be built to avoid problems.

building design, air leakage

#NO 11718 Computer simulations look good for "cathedralized" attics.

Anon

USA, Energy Design Update, September 1998, pp 6-10.

Describes research which shows that sealed attics can be used in hot climates without any energy penalty, in houses that have ductwork located in the attic. Sealed or "cathedralised" attics are insulated on the sloped plane of the roof rather than on the ceiling below. The roof decking, building paper, flashing and shingles provide the air seal at the top of the house. With no vents to the outside, the attic becomes a conditioned space. 

attic, insulation

#NO 11721 Digital control system for extreme low energy apartments.

Liem S H, van Paassen A H C

in: 19th International Congress of Refrigeration, Den Haag 20-25 August, 1995, p 224.

In the framework of IEA Task XIII, a pilot project URBAN VILLA has been realised in Amstelveen, The Netherlands. This project concerns the development of an apartment building of 42 luxurious apartments, of which 16 will have extreme low energy consumption. The total primary energy consumption of these apartments is estimated at 3675 kWh/a of natural gas: for space heating 920 kWh/a, domestic hot water system 1630 kWh/a and pumps and the ventilators 1125 kWh/a. In order to achieve the goal, the apartments were very well insulated, used triple low energy glass and great care was taken to prevent air infiltration. An atrium, equipped with a sun protection screen, controllable flaps on the roof, upper and lower side of the facade, was used to preheat the air that comes into the apartments and a solar collector system to preheat the domestic hot water demand. In the winter balanced ventilation with heat recovery was used and in the summer natural ventilation with open windows. A high efficiency boiler was used for the domestic hot water and central heating system; spiro tube convectors were used to bring the rooms quickly to temperature.

low energy housing, apartment building

#NO 11731 UK Building Regulations 1991 Ventilation (1995 edition) F1 Means of Ventilation. F2 Condensation in roofs.

UK Department of the Environment

UK, HMSO, 1995, 16 pp.

Replaces the 1990 edition. The main changes are: Background ventilation defined more clearly, provisions improved and the range of examples expanded; passive stack ventilation introduced as an alternative option to mechanical extract ventilation for domestic kitchens, bathrooms and sanitary accommodation; guidance on the use of open-flued combustion appliances for extract ventilation added; provision for opening windows in kitchens added as a supplement to extract ventilation; ventilation of utility rooms added; guidance clarified on reducing the risk of flue gas spillage from open-flued appliances due to mechanical extract ventilation; ventilating to a courtyard omitted; ventilation of common spaces in buildings containing two or more dwellings omitted; provision for ventilation of non-domestic buildings introduced.

building regulations, roof, condensation

#NO 11732 UK Building Regulations 1991 Conservation of fuel and power (1995 edition) L1.

UK Department of the Environment

UK, HMSO, 1995, 72 pp.

Replaces the 1990 edition. The main changes are as follows: The standards of fabric insulation have been improved by changing the method for calculation of U-values to take account of thermal bridges such as mortar joints, timber joists and studs. The U-value standard for windows, doors and rooflights has been based on double rather than single glazing. Variation from the standard is permitted if compensating provisions are made. The window area allowances have been changed and now include windows, doors and rooflights. Increases over the basic area allowances are permitted if compensation provisions are made. New provisions are included for reducing thermal bridging around window and door openings. New provisions are included for reducing air leakage at windows and doors and through the building fabric. The standards for the thermal performance of hot water vessels and pipework and ductwork have been improved. In relation to dwellings only: For dwellings three methods are given for demonstrating appropriate provision; the elemental method has been retained but the simple trade-off between double-glazing and lower standards of wall, floor and roof insulation is no longer available. Two levels of insulation are shown; the appropriate level depends on the SAP Energy Rating. Calculation procedure 1 has been replaced by the Target U-value method which provides a U-value for the exposed fabric as a whole and permits designers to take account of solar gain and more efficient heating systems if desired. Two targets are given; the appropriate level depends on the SAP Energy Rating. For dwelling the Energy Use Approach is replaced by an Energy Rating method which sets appropriate SAP Energy Rating targets dependent upon building size. Provisions for the control of heating and hot water systems have been extended so that space temperatures and the provision of hot water can be more flexibly controlled. New provisions for conservatories apply where conservatories form an integral part of a new dwelling. The roof U-value standard has been improved and a U-value standard is given for commercial vehicle access and similar large doors. A new section gives guidance on achieving the requirements for lighting efficacy and controllability. Guidance is now given regarding appropriate provisions when undertaking material alterations and changes of use.

building regulations, energy conservation

#NO 11876 Ventilation, humidity, and energy impacts of uncontrolled airflow in a light commercial building.

Withers C R, Cummings J B

USA, ASHRAE, 1998, in: the ASHRAE Transactions CD, proceedings of the 1998 ASHRAE Annual Meeting, held Toronto, Canada, June 1998, 10 pp, 5 figs, 3 tabs, refs.

A small commercial building was monitored before and after energy-saving retrofits to study the impact of retrofits upon ventilation rates, humidity, building pressure, and air-conditioning energy use. Duct airtightness testing identified severe duct leakage as a significant source of uncontrolled airflow. Differential pressure and infiltration measurements using tracer gas indicated an attic exhaust fan as another significant source of uncontrolled airflow. Duct repair results in a 31% drop (30.5 kWh/day) in cooling energy and an increase in relative humidity from 72% to 76%. Turning off the attic exhaust resulted in an additional 36% energy savings (14.3 kWh/day), including fan power, and a decrease in relative humidity from 76% to 58%. Turning off the attic exhaust fan also significantly reduced the ventilation rate in the building by about 62% from pre-retrofit ventilation measurements. The study of this building before and after retrofits illustrates the impacts that air leakage can have on light commercial buildings with nonairtight ceilings, the importance of using good diagnostics to discover all sources of uncontrolled airflow in buildings, and the importance in understanding what the duct zone environment is like in small commercial construction.

humidity, commercial building, retrofitting, ventilation rate

#NO 11877 Building cavities used as ducts: air leakage characteristics and impacts in light commercial buildings.

Cummings J B, Withers C R

USA, ASHRAE, 1998, in: the ASHRAE Transactions CD, proceedings of the 1998 ASHRAE Annual Meeting, held Toronto, Canada, June 1998, 10 pp, 1 fig, 2 tabs, refs.

Field testing in 70 small commercial buildings in central Florida identified that building cavities were used as part of the air distribution system in 33 buildings. The various building cavity types (number of buildings in parentheses) are: enclosed air-handler support platforms (10), mechanical closets (8), mechanical rooms (6), ceiling spaces (7), wall cavities (6), chases (1), and "other" building cavities (2). Testing found that these building cavities are considerably more leaky than standard ducts and plenums because they are generally not built to the same airtightness standard as ducts. Actual air leakage is a function not only of duct hole size but also pressure differential across the leak sites. Pressure differentials generally range from -0.080 in.WC (-20 Pa) to -0.401 in.WC (-100 Pa) in support platforms, mechanical closets and rooms, wall cavities, and chases. By contrast, ceiling plenums often operate at less than 0.004 in.WC (1 Pa) difference from the occupied space and sometimes at positive pressure with respect to outdoors.

The energy, infiltration, and relative humidity impacts of building cavity duct leakage depend upon the leak airflow rate and the temperature and humidity conditions of the air entering the leaks. Therefore, the location of the building cavity ducts is very important. If the return leak air is drawn from the occupied space, that leakage will have little or no impact on energy, infiltration, or relative humidity. At the other extreme, if the leaking air comes from a hot and humid attic space, the impacts will be large. The interaction of various building cavity duct leaks with eight different building configurations - based on the location of the primary air and thermal boundaries in the ceiling space - is discussed here. The paper concludes that building cavities should not, as a general rule, be used as a part of the air-distribution system. The exception is use of ceiling space return plenums. Ceiling plenums can be designed to operate at near neutral pressure with respect to outdoors and, therefore, can experience little or no duct leakage. 

duct, building cavity, air leakage, commercial building

#NO 11881 Measuring adjacent building effects on laboratory exhaust stack design.

Wilson D J, Fabris I, Ackerman M Y

USA, ASHRAE, 1998, in: the ASHRAE Transactions CD, proceedings of the 1998 ASHRAE Annual Meeting, held Toronto, Canada, June 1998, 16 pp, 22 figs, 1 tab, refs.

Current methods for designing exhaust stack height and exit velocity are based on avoiding contamination of the roof, walls, and nearby ground surface of the building on which the stack is located. Usually, no account is taken of the effect of adjacent buildings that add turbulence and increase dispersion if they are located upwind and may be contaminated themselves if they are downwind of the emitting building. To account for these adjacent building effects, ASHRAE Research Project 897 used water-channel simulation of the atmosphere to evaluate rooftop contamination in more than 1,700 different configurations of adjacent building height, width, spacing, stack location, stack diameter, height, and exit velocity. Exhaust stacks on scale models of flat-roof buildings were tested using fluorescent dye tracer illuminated by thin laser light sheets, with digital video images to measure dilution in the exhaust plume at roof level air intake locations. The results show that high stacks and exit velocities that represent good design on an emitting building can be less effective and are sometimes counterproductive in reducing contamination of the roof of a nearby adjacent building. The implications of the study for developing practical stack design guidelines are discussed in this paper.

laboratory, exhaust stack

#NO 11882 Instrumentation and measurement of airflow and temperature in attics fitted with ridge and soffit vents.

Romero M I, Brenner R J

USA, ASHRAE, 1998, in: the ASHRAE Transactions CD, proceedings of the 1998 ASHRAE Annual Meeting, held Toronto, Canada, June 1998, 10 pp, 12 figs, refs.

This study established a research facility where airflow velocities, temperature, and differential pressures could be measured at the ridge of an attic. Following the construction of a test building, sensors were constructed, calibrated, and installed inside the attic. Paired tests were performed for three different ridge vent treatments; two were rolled type vents and one was a baffled vent. When both attics were fitted with the same ridge vent, the airspeed and differential pressure profiles at the ridge were very similar for both attics, indicating that any observed differences in airspeed and differential pressure were caused by the ridge vent treatment used. The baffled vent and rolled vents were then installed on the ridge of the west and east attics, respectively.

The data demonstrated that the baffled ridge vent provided a minimum of twice the ridge airspeed of the rolled vents, when all wind conditions were considered. On the day selected to study the direction of the airflows at the ridge, the baffled vent had airflow speeds at the ridge similar to the rolled vent without fabric backing. The baffled vent allowed air to come out of the attic through both sides of the ridge (negative differential pressures on both sides), while the rolled vent without fabric backing caused air to enter through the south side of the ridge and exit through the north side (positive differential pressure on the south side and negative differential pressure on the north), in effect short-circuiting the vent. The fabric backed rolled vent allowed attic air to come out of the attic through both sides of the ridge, as did the baffled vent, but the airspeed was slower. The baffled vent was the one with the highest airspeed at the ridge and also had both sides of the vent under negative differential pressure, providing the most effective ventilation.

instrumentation, air flow, attic, vents

#NO 11883 Roof ventilation to prevent problematic icings at eaves.

Buska J, Tobiasson W, Greatorex A

USA, ASHRAE, 1998, in: the ASHRAE Transactions CD, proceedings of the 1998 ASHRAE Annual Meeting, held Toronto, Canada, June 1998, 8 pp, 15 figs, refs.

Attic ventilation 1/150 and 1/300 rules of thumb were established to avoid problems from indoor moisture. In cold regions another strong reason to ventilate roofs that slope to cold eaves is to prevent the formation of problematic icicles and ice dams. Building heat, not the sun, is responsible for the large icings that cause such problems, and roof ventilation is a direct and effective way of solving them.

The authors have instrumented buildings to determine attic ventilation needs to minimize icings and have developed design guidelines for natural and mechanical ventilation systems. These guidelines have been applied to roofs with cathedral ceilings, two of which are discussed in detail. Head losses in narrow airways complicate the ventilation of cathedral ceilings. It is particularly difficult to ventilate the valley areas of such roofs. However, as these case studies indicate, ventilation systems can be developed to eliminate problematic icings on complex roofs. Details often determine the success or failure of ventilation systems.

roof ventilation, cold climate

#NO 11884 Effects of radiant barriers and attic ventilation on residential attics and attic duct systems: new tools for measuring and modelling.

Petrie T W, Wilkes K E, Childs P W, Christian J E

USA, ASHRAE, 1998, in: the ASHRAE Transactions CD, proceedings of the 1998 ASHRAE Annual Meeting, held Toronto, Canada, June 1998, 17 pp, 6 figs, 4 tabs, refs.

A simple duct system was installed in an attic test module for a large-scale climate simulator at a U.S. national laboratory. The goal of the tests and subsequent modeling was to develop an accurate method of assessing duct system performance in the laboratory, enabling limiting conditions to be imposed at will and results to be applied to residential attics with attic duct systems.

Steady-state tests were done at a severe summer condition and a mild winter condition. In all tests the roof surface was heated above ambient air temperatures by infrared lights. The attic test module first included then did not include the duct system. Attic ventilation from eave vents to a ridge vent was varied from none to values achievable by a high level of power ventilation. A radiant barrier was attached to the underside of the roof deck, both with and without the duct system in place. Tests were also done without the radiant barrier, both with and without the duct system. When installed, the insulated ducts ran along the floor of the attic, just above the attic insulation and along the edge of the attic near the eaves and one gable.

Air temperatures were measured from the ridge to the insulation surface along the center of the test module at all ventilation rates. For all tests, air temperatures inside the ducts, as well as attic air, attic insulation, and gable and deck temperatures, were measured and compared to the predictions of the model. Only average attic air temperatures were compared since the model did not include stratification. The ducts were placed along the eaves in the test module. This is thought to exacerbate stratification in these tests more than the placement of ducts in real attics would. The ducts along the eaves partially blocked the path for ventilation air to mix with attic air near the insulation between the ducts. 

Despite adequate duct insulation, the duct system kept attic conditions cooler in summer and warmer in winter. Since the infrared lights were heating the roof above ventilation air temperatures at all conditions, increasing ventilation caused attic air and insulation surface temperatures to decrease. At the milder winter condition, compared to measurements with no radiant barrier attached to the underside of the deck but with the ducts installed, there was an average 37% increase in heat loss into the attic with the radiant barrier and ducts in place. This heating penalty varied randomly with ventilation rate in these tests. At the severe summer condition simulated in the tests, the radiant barrier decreased the heat gain through the ceiling. The average cooling benefit was 34% with ducts in the attic and 29% without them. Variation with ventilation rate was again random, but there was less variation than at the mild winter condition.

These tests in a climate simulator achieved careful control and reproducibility of conditions. This elucidated dependencies that would otherwise be hidden by variations in uncontrolled variables. Based on the comparisons with the results of the tests at the milder winter condition and the severe summer peak condition, model predictions for attic air and insulation temperatures should be accurate within +/-10 Deg.F (+/-6 Deg.C). This is judged adequate for design purposes and could be better when exploring the effect of changes in attic and duct parameters at fixed climatic conditions.

radiant barrier, attic, ducts

#NO 11885 Vented and sealed attics in hot climates.

Rudd A F, Lstiburek J W

USA, ASHRAE, 1998, in: the ASHRAE Transactions CD, proceedings of the 1998 ASHRAE Annual Meeting, held Toronto, Canada, June 1998, 12 pp, 14 figs, 9 tabs, refs.

Sealed attic construction, by excluding vents to the exterior, can be a good way to exclude moisture-laden outside air from attics and may offer a more easily constructed alternative for air leakage control at the top of residential buildings. However, the space conditioning energy use and roof temperature implications of this approach have not been extensively studied. A computer modeling study (Rudd 1996) was performed to determine the effects of sealed residential attics in hot climates on space conditioning energy use and roof temperatures. The one-dimensional, finite element computer model (FSEC 1992) contained an attic model developed and validated by Parker et al. (1991). Empirical modifications were made to the attic model to provide better alignment with measured ceiling heat flux reductions of ventilated attics with respect to sealed attics for summer peak days from three roof research facilities (Beal et al. 1995; Rose 1996; Fairey 1986). Annual and peak cooling day simulations were made for the Orlando, Florida, and Las Vegas, Nevada, climates, using a 139 square metre (1500 square feet) slab-on-grade ranch style house with wood frame construction. Results showed that, when compared to typically vented attics with the air distribution ducts present, sealed "cathedralized" attics (i.e., sealed attic with the air barrier and thermal barrier [insulation] at the sloped roof plane) can be constructed without an associated energy penalty in hot climates. 

attic, hot climate

#NO 11888 Stack-driven moisture problems in a multi-family residential building.

Clarkin M E, Brennan T M

USA, ASHRAE, 1998, in: the ASHRAE Transactions CD, proceedings of the 1998 ASHRAE Annual Meeting, held Toronto, Canada, June 1998, 6 pp, 4 figs, refs.

Wintertime window condensation problems were reported on the top two floors of a five-story, multi-unit residential building in central New York (7200, base 65 Deg.F heating degree-days). Initially built as a five-story brick hotel at the turn of the century, the building was rehabbed into low-income apartments in the early 1990s. Ventilation in each unit consisted of operable windows and a single bath exhaust. Condensation on windows was severe enough to support fungal contamination in the first winter of occupancy. During the renovation, vinyl-clad aluminium sash, double-hung, double-pane windows were installed to replace the original wood sash round-tops. Initial efforts to solve the problem included improving sealing and insulation details around the retrofitted windows on the fourth and fifth floors. The amount and duration of condensation was reduced, but condensation and new fungal growth occurred during the next winter. A more detailed investigation of the problems was then made. It was determined that the neutral pressure plane was in the center of the third floor of the building. A large fraction of the ventilation air for the upper three floors came from the floors below. This resulted in progressively higher relative humidity as air ascended through the building. Tested bath fans were moving less than 10 cfm (5L/s). Surface temperature maps were made of windows and sheetrock. Poor ventilation, deep window returns, and windows with insulating details inappropriate for this climate resulted in condensation and fungal growth. Pressurization tests were conducted on a design day to determine how much exhaust it would take to raise the neutral pressure plane above the roof of the building.

stack pressure, moisture, apartment building

#NO 11891 Placement of ventilation air intakes for improved IAQ.

Rock B A, Moylan K A

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 9 pp, 5 figs, 1 tab, refs.

ASHRAE Research Project 806, Design Criteria for Building Ventilation Inlets, reviews existing knowledge of the placement of ventilation air louvers, produces a design guide, and suggests additional research, all with the intention of improving indoor air quality in commercial and institutional buildings. Decisions about intake and exhaust placements made early in the architectural and HVAC system design processes will impact occupants over the life of a building. Such placment decisions, therefore, require proper consideration. There is little guidance currently available to designers, but research efforts in this area are expanding.

Previous research efforts and standards relating to ventilation air intake placement are described in this paper. However, more extensive coverage and a lengthy bibliography are provided in the project's "Literature Report". In "A Designer's Guide to Placement of Ventilation Air Intake Louvers" for the project, the phenomena, standards, and design experiences that affect the placement of intake air louvers are reviewed using less technical text, many graphics, and example calculations.

More research is needed on ventilation intake placement for common commercial HVAC systems with rooftop, through-the-wall, and at-grade louvers. Most existing knowledge is derived from the many studies on industrial stack exhaust-gas reentrainment and not common HVAC geometries. The findings of such future research and a summary of this project's "Designer's Guide" need to be included in future revisions of ASHRAE Handbook chapters.

air intakes

#NO 11907 Influence of architectural screens on rooftop concentrations due to effluent from short stacks.

Petersen R L, Carter J J, Ratcliff M A

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 9 pp, 6 figs, 5 tabs, refs.

This paper describes the wind tunnel study conducted on behalf of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to evaluate and quantify the effect of architectural screens on rooftop concentration levels due to effluent from short stacks. An equivalent stack height (ESH) concept is introduced, which is used to develop a stack height reduction (SHR) factor that may be used in conjunction with existing stack design procedures found in the 1997 ASHRAE Handbook - Fundamentals to account for the presence of architectural screens.

wind tunnel, stack effect

#NO 11916 Conclusions from ten years of Canadian attic research.

Fugler D W

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 7 pp, 11 figs, refs.

Canada Mortgage and Housing Corporation (CMHC) conducted a series of attic research projects from 1988 to 1997. Initially, there were few field test data to substantiate how attics dealt with air and moisture transfer. The CMHC research developed a test protocol for attic airtightness and air change testing and then proceeded to field testing of a variety of attics in different climatic areas. An attic model, ATTIX, was referenced against test hut data and used to simulate attic performance across Canada. The latest research project compared the performance of nominally identical attics, one of each pair with full, code-required venting and one with all intentional holes sealed.

Results show that ventilation plays a relatively small part in the control of attic moisture and temperature but, conversely, rarely provokes major moisture problems. This suggests that there is no significant advantage in changing current Canadian attic code requirements, except perhaps by allowing more flexibility in venting design.

attic, moisture, air tightness, modelling

#NO 11917 A preliminary experimental assessment of the comparative thermal performance of attics and cathedral ceilings in a cold climate.

Goldberg L F, Huelman P H, Bridges B B

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 11 pp, 6 figs, 2 tabs, refs.

This paper describes a residential research facility built for the experimental measurement of the relative energy and moisture performance of various residential building envelope components and systems. The building comprises 12 test bays on an east/west axis bounded on each end by a guard bay. The eastern six test bays are framed in steel, and the western six bays are framed in wood. Each half of the building contains a symmetrical mix of vented and unvented cathedral and attic roofing systems and is built above a heated basement. During the heating season, the entire building is maintained at a uniform temperature within +/- 0.9 Deg.F (+/-0.5 K) by a computer control system and data are stored with an aggregation period of approximately 20 minutes. The thermal performance phenomenology of a vented attic and cathedral ceiling are analyzed via heat transfer and mass flux parameter correlations. Attic and cathedral ceiling roofing system relative thermal integrities are compared as a function of framing material and ventilation status. Within the preliminary context of the data reported, it appears that metal framing yields a lower thermal integrity than wood framing with particularly poor performance when applied to a vented cathedral ceiling. The ridge vent mass flux in ventilated attics and cathedral ceilings is shown by the data reported to be largely independent of roof configuration.

thermal performance, attic, cold climate

#NO 11918 Heat and moisture response of vented and compact cathedral ceilings: a test house evaluation.

Hens H, Janssens A

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 13 pp, 12 figs, 7 tabs, refs.

In the last decade, public awareness of the greenhouse effect has pushed the building sector toward higher energy efficiencies. This move has had consequences for roofs with a cathedral ceiling. A U-factor in the vicinity of 0.2 W/(square metre .K) instead of 0.6 W/(square metre .K) became the new target value. The move toward such a low U-factor for cathedral ceilings was evaluated in an extended test house program. The major objective of the research was to find answers to the following three questions: (1) What is the impact of air ingress and wind washing on the hygrothermal performance and durability of such well-insulated roofs? (2) Is a vented air space above the thermal insulation needed to prevent concealed condensation? (3) Is a vapor retarder underneath the insulation equally efficient?

The traditional answer to questions (2) and (3) is built on five assumptions: (1) heat is transported through all materials by conduction only, (2) moisture moves through the materials by diffusion only, (3) air ingress is restricted to the air space, (4) outside air ventilation functions under all circumstances, and (5) it always means additional drying capacity. The test house measurements confirmed that in the cool, maritime climate of Western Europe, air ingress and wind washing over-throw assumptions (1), (2), and (3). As assumptions (4) and (5) are not true under all circumstances. The research resulted in the redrafting of the performance requirements for highly insulated roofs with a cathedral ceiling.

attic, moisture

#NO 11919 Issues related to venting of attics and cathedral ceilings.

TenWolde A, Rose W B

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 7 pp, refs.

Current model building codes require attic ventilation in all U.S. climates. Originally, these requirements were strictly based on concerns for condensation in attics during winter in cold climates, and they were based on limited technical information. Nevertheless, attic ventilation has become the uncontested strategy to minimize condensation and ice dams during winter and extreme attic temperatures during summer. However, other strategies exist that address each of these problems as well as or better than attic ventilation. This paper examines issues such as summer attic temperatures, ice dams, and shingle durability and discusses the relative merits of attic ventilation compared to alternative design approaches in various climates. The authors support current recommendations for attic ventilation in cold and mixed climates but recommend that attic ventilation be treated as a design option in warm, humid climates. The authors review the new information on attic and roof ventilation in the 1997 ASHRAE Handbook - Fundamentals and discuss the reasons for the changes.

attic, ceiling, ventilation system, condensation

#NO 11920 Test and evaluation of the attic temperature reduction potential of plastic roof shakes.

Holton J K, Beggs T R

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 9 pp, 9 figs, 4 tabs, refs.

While monitoring the comparative performance of two test houses in Pittsburgh, Pennsylvania, it was noticed that the attic air temperature of one house with a plastic shake roof was consistently 20 Deg.F (11 Deg.C) cooler than its twin with asphalt shingles during peak summer cooling periods. More detailed monitoring of the temperatures on the plastic shake, the roof deck, and the attic showed this effect to be largely due to the plastic shake and not to better roof venting or other heat loss mechanisms.

attic, cooling, roofing material

#NO 11922 Distribution system leakage impacts on apartment building ventilation rates.

Walker I S

USA, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc (ASHRAE), 1999, in: the ASHRAE Transactions CD, proceedings of the 1999 ASHRAE Winter Meeting, held Chicago, USA, January 1999, 13 pp, 5 figs, 8 tabs, refs.

Forced air distribution systems in residential buildings are often located outside the conditioned space, for example, in attics, crawl spaces, garages, and basements. Leaks from the ducts to these unconditioned spaces or outside can change flows through the registers and change the ventilation rates of the conditioned spaces. In this study, duct leakage flows were measured in several low-rise apartment buildings. The leakage flow measurements and other data about the apartments were used to develop a prototype apartment building, The multizone airflow model COMIS was then used on this prototype building to determine internal flows within the building, airflows through the building envelope, and the impacts of the duct leakage on the ventilation rates. The effects of sealing the duct leaks were also examined in order to determine changes in infiltration rates resulting from duct retrofits. The simulation results showed that for the prototype tested here, the excess return leakage tended to decrease envelope infiltration flows by about 20%, but the total infiltration load, including return duct leaks, more than doubled during system operation.

duct leakage, apartment building, ventilation rate

#NO 11931 Spatial variability of pollution induced by traffic in street canyon.

Flori J-P, Sacre C

in: UK, Air Infiltration and Ventilation Centre, proceedings of "Ventilation Technologies in Urban Areas", 19th Annual Conference - Supplement, held Oslo, Norway, 28-30 September 1998.

Concentration of pollutants produced by car traffic in a street below the roof level has large spatial variations. In a street, pollutants are diluted by the turbulent air flow which is induced by the wind speed above the roof level, and also produced by car displacement. The airflow structure is in relation with street size and building shape. Particularly strong gradients of concentrations can be observed vertically and also horizontally in front and along buildings where are set up ventilation inlets and windows. So it is necessary to take into account this variability to consider the influence of outdoor air upon indoor air quality. The street canyon case has been studied extensively in recent years by CSTB and many other authors. A bibliographical synthesis is presented, including results from field measurements, wind tunnel experiments and numerical simulation.

outdoor air, pollutant, motor vehicle

#NO 11936 Measuring energy savings of a comprehensive retrofit in an existing Florida residence.

Parker D S, Sherwin J R, Sonne J K, et al

USA, American Council for an Energy Efficient Economy (ACEEE), 1998, in: proceedings of "Energy Efficiency in a Competitive Environment", the 1998 ACEEE Summer Study on Energy Efficiency in Buildings, CD format, pp 1.235-1.251, 21 figs, 6 tabs, refs.

Simulation analysis suggests that electricity consumption can be reduced up to 40% in existing Florida homes. To test this theory, an all-electric home was located in Miami, Florida upon which to perform a variety of retrofits. The total annual electricity consumption on the one year base-line period preceding the study was 20,733 kWh. Detailed instrumentation and metering equipment was installed in May of 1995 so that each energy end-use could be evaluated. A year of baseline monitoring was followed by installation of a battery of retrofits: radiant barrier with additional attic ventilation, a SEER 15 air conditioner, an add-on solar water heating system, a super efficient refrigerator, a smaller, more efficient pool pump and compact fluorescent lighting.

The results showed a 40-45% reduction in measured daily energy use (28.6kWh/day). Annual savings were between 8.000 and 10.300 kWh depending on the base year of reference. Space cooling was reduced by 42% and water heating by more than 70%.

energy saving, retrofitting, residential building

#NO 11978 The effect of building fan operation on indoor-outdoor dust relationships.

Weschler C J, Kelly S P, Lingousky J E

APCA Journal, Vol 33, No 6, June 1983, pp 624-629, 1 fig, 4 tabs, 11 refs.

As part of an energy conservation program recently implemented by the Bell System, fans in many telephone equipment buildings now operate only when necessary to bring the temperature within allowable limits, rather than continuously. In the study reported here the effects of fan operation on indoor-outdoor dust relationships were monitored at 2 representative telephone offices. Automatic dichotomous samplers were used to collect fine and course aerosol particles inside telephone equipment buildings at Wichita, KS and Lubbock, TX. At both sites, outdoor samples (roof top) were collected at the same time as the indoor samples. During the tests the building fans were repetitively cycled between 2-week intervals of continuous fan operation and 2-week intervals of intermittent fan operation. The indoor dust concentrations typically increased when the fans were off. The results indicate that this increase was due to loss of constant filtration, but not due to loss of building pressurisation (i.e., filtration of the re-circulated air is largely responsible for the lower dust levels when the fans are running continuously). An expression is derived for the relative dust increase when the building fans are switched off.

Among other factors, the relative increase is directly proportional to the efficiency of the building filters and to the rate at which air is re-circulated through them. The present findings can be extended to similar buildings.

dust, outdoor air, indoor air quality, fan

#NO 11987 Air, contaminant and heat transport models: integration and application.

Dorer V, Weber A

UK, Energy and Buildings, No 30, 1999, pp 97-104, 11 figs, 9 refs.

Comfort evaluations cover air quality, thermal, visual and acoustic comfort. Today, only few computer programs allow for the integrated evaluation of several or all relevant parameters. Heat transport, ventilation as well as lighting in a room are influenced by each other. Therefore they should be integrally modelled. As part of the IEA-ECBCS Annex 23 'Multizone Airflow Modelling', such a coupling has been realised by integrating the air flow and contaminant transport simulation code of COMIS into the building and systems simulation code TRNSYS. This paper gives a short description of the concept used for the coupling. Then, two application examples typical for a building design study situation are presented, the first being a multi-storey school building which was passively cooled at night due to natural stack airflow. In the second example the facade of the same building was retrofitted with a glazed outer facade. Ventilation as provided by naturally driven shaft ventilation through the facade spaces. For such cases as described in the examples, it may be necessary due to the complex interactions, to study many configurations to find optimum control strategies for the openings and the blinds with respect to overheating risk as well as to air quality. For the upper floors, the risk of overheating and low air quality may be difficult to minimise without extending the shaft above roof level.

multizone air flow modelling, building simulation, passive cooling

#NO 11994 Building America: real-world results.

Anon

USA, Home Energy, January/February 1999, pp 24-27, 2 figs, 4 tabs.

Describes energy efficiency results of a group of production homes built to Building America specifications, which have been studied in normal operation by Building Science Corporation. The so-called "Snapshot" testing method involves tracking utility bills and measuring how long the water heaters and ventilation systems are on, as well as monitoring return air temperatures in the first- and second-floor return ducts; basement temperatures; and how often the thermostats call for heat, cooling, or activation of air handler fans. Comments on comfort were also sought from the homeowners. Houses in the Chicago development, designed specifically for Chicago's cold climate, saved energy beyond their designers' expectations. For the hot climate of Las Vegas, simple improvements were introduced including modification of the HVAC system. Air conditioner size was reduced by around 2 tons as a result of envelope modifications and correct load calculations. Unusually, unvented roofs were used to reduce duct leakage to the outside.

residential building, production home, testing, energy efficiency

#NO 12000 Builders find new technologies paying off.

Anon

USA, Home Energy, January/February 1999, pp 18-23, 2 tabs.

Describes how builders across the United States are seeing strong sales of homes that can reduce heating and cooling bills by as much as 50% but cost about the same as conventional homes to build. In the process of designing, building and analysing these homes, lessons have been learned about systems engineering that all builders can put into practice. One of the advantages of the Building America program is that, with the variety of groups involved, many different ideas have been explored and tested out. The consortia start out by creating pilot homes through reengineering one or two houses, while monitoring and testing one of the builder's standard houses as a reference. Once the pilots are built, the consortia collect feedback. The consortia also determine how comfortable the houses are, and how well the tradespeople working with the builder members adapt to the new techniques and designs. The most important final question is whether the new design costs more or less to build. One of the consortia showed that unvented roofs perform better than vented roofs in hot-dry and hot-humid climates. They also showed that in many cases, houses don't need a fully distributed return duct system, that supply ventilation works better than exhaust ventilation, that supply ventilation with dehumidification is necessary for controlled ventilation in hot-humid climates, that polyethylene vapour barriers are generally a bad idea, and that batt insulation in basements is always a bad idea because it causes mould problems. The building costs have sometimes been slightly higher than standard houses. 

residential building, energy efficiency

#NO 12102 Natural ventilation of attic space for solar heat removal - heat and air flows along lower surface of a roof.

Yamamoto K, Homma H

Sweden, Stockholm, KTH Building Services Engineering, 1998, proceedings of Roomvent 98: 6th International Conference on Air Distribution in Rooms, held June 14-17 1998 in Stockholm, Sweden, edited by Elisabeth Mundt and Tor-Goran Malmstrom, Volume 2, pp 409-414, 9 figs, refs.

In a hot climate, a large amount of solar heat irradiates on a roof, and it is transmitted to an occupied space beneath it through an attic. To interrupt this heat to attain a comfortable condition in the occupied space, ventilation of the attic is an important and effective measure. There are two ways of the ventilation, one is natural and the other is forced ventilation. The former measure should be considered prior to the latter from such reasons as simplicity in practice and power saving. Even though forced ventilation is applied, the natural air movement in the attic should be known to attain intended effect in forced ventilation.

In this study, the air and heat movements by natural convection were searched for with two electrically heated plates in a laboratory. The heat flux on the surface, incline angle of the plates and aperture on the top joint of the plates were variables in the experiments.

The velocity and temperature measurement and flow pattern observation indicated that an aperture of 50 mm or above is required to evacuate the heat absorbed air to cool the lower surface of a roof effectively.

air flow pattern, full scale experiment, natural ventilation

#NO 12157 Greenhouse natural ventilation by buoyancy forces.

Haxaire R, Roy J C, Boulard T, Lamrani M A, Jaffrin A

EPIC '98, Volume 2, pp 522-527, 10 figs, refs.

Convective transfers mainly determine the energy and mass balances which regulate the micro-climate inside a greenhouse. Air flow and temperature patterns induced by natural ventilation through greenhouse roof openings are only considered here. Flow visualisations were performed on a half scale test cell simulating the absorption of solar radiation at the floor surface of a single-span greenhouse. Temperature and air flow patterns were observed in a steady regime i) with a single sided roof vent and ii) with two symmetrical ones. An air inflow always take place at the lower part of the openings and feed a single convective loop which follows the walls of the greenhouse before escaping through the upper part of the vents. These natural convective patterns were numerically simulated by models of a Computational Fluid Dynamic code (CFD 2000T""). It was found that the convective cell, velocity values and the temperature profiles were generally in good agreement with the experimental results.

natural ventilation, heat transfer, roof

#NO 12163 The design of roof mounted wind driven combined intake and extract ventilators.

Gage S

EPIC '98, Volume 2, pp 691-698, 14 figs, refs.

Reports on work being undertaken as part of a UK government funded research programme into passive ventilation in urban environments. In this type of environment air must be taken into buildings from the top to reduce pollution risks, especially those associated with fine particles. These risks reduce with height. The risks of noise pollution and burglary are also reduced. The forces which drive this type of ventilation have been described in another paper. In the absence of wind a gravity displacement system will induce airflow. It is also most important that wind pressures do not run counter to gravity displacement air flows. A very reliable way of achieving this is to combine air intake and extract in the same piece of equipment. Wind driven devices have been proposed to achieve this, but no devices have been constructed and tested. There are a number of practical issues that need to be studied and problems that need to be overcome before this type of equipment can be fabricated commercially. If successful this type of equipment may also be sued to drive air through low resistance active cooling and heat recovery units.

air intake, air extract, roof

#NO 12195 Relation between building envelope U-value and building form.

Yilmaz Z, Koclar Oral G, Manioglu G

UK, Garston, BRE, 1999, proceedings of Indoor Air 99, the 8th International Conference on Indoor Air Quality and Climate, and the Air Infiltration and Ventilation Centre (AIVC) 20th Annual Conference, held Edinburgh, Scotland, 8-13 August 1999, Volume 1, pp 59-63.

This study aims to introduce a methodology which enables to revise the limit values of overall heat transfer coefficient in accordance with the building form from thermal comfort and energy conservation point of view. In order to prevent excess heat loss, building should be designed as passive heating system. Overall heat transfer coefficient (U-value) of building envelope and building form can be considered as the most important parameters of the passive heating system. Therefore, U-value of building envelope should be determined depending on building form. Building form can be defined basing on the shape factor (the ratio building length to building depth), height and roof type. It is possible to determine a lot of building forms which yields same volume, but different facade area. Therefore, the ratio of building volume to total facade area (V/A) is the best indicator describing the building form. Thus, U-value of building envelope should be determined in accordance with the ratio of V/A. In this study a methodology which aims to determine the limit values of building envelope U-value in accordance with the ratio of V/A is introduced.

building envelope, thermal comfort, building design, building shape

#NO 12224 Modelling methods of building process.

Krutkeviciute O, Viliunas G

UK, Garston, BRE, 1999, proceedings of Indoor Air 99, the 8th International Conference on Indoor Air Quality and Climate, and the Air Infiltration and Ventilation Centre (AIVC) 20th Annual Conference, held Edinburgh, Scotland, 8-13 August 1999, Volume 1, pp 755-759.

Investigation the modelling of the mathematical model of expediency of project decisions of building materials including the human safety the asbestos. The asbestos is most widely used in the production of roof cover-slate. At this moment the building materials in which composition the asbestos is used, become the actual ecological and economical problem of the country. There is created the economical mathematical model there were modelled various building process of work with the asbestos, the alternative variants of those process by estimating quantitatively the building processes and the amount of the asbestos must be reduced up to the minimum. Applying this solution of mathematical modelling and optimisation to the real building process was created a plane of means for avoiding of a harmful influence of the asbestos to the human organism. 

modelling, building materials

#NO 12227 Numerical analysis of natural convection in insulating porous material.

Shankar V, Hagentoft C E

UK, Garston, BRE, 1999, proceedings of Indoor Air 99, the 8th International Conference on Indoor Air Quality and Climate, and the Air Infiltration and Ventilation Centre (AIVC) 20th Annual Conference, held Edinburgh, Scotland, 8-13 August 1999, Volume 1, pp 768-773.

The 'Paper deals with numerical computations, carried out, in order to predict the effects of natural convection on the thermal performance of porous material. In this paper the effect of natural convection in a horizontal porous layer will be discussed. The study of the above configuration is essential to understand the functioning of insulation of the type used in attics. The influence of natural convection on the thermal properties of mineral wool, loose-fill insulation, insulation made of small and large polystyrene balls are studied. The results are presented in terms of dimensionless numbers and the temperature distribution across the insulation.

insulation, building materials

#NO 12281 Long-term testing of gas adsorption filters for ventilation systems.

Ekberg L E, Strindehag O

UK, Garston, BRE, 1999, proceedings of Indoor Air 99, the 8th International Conference on Indoor Air Quality and Climate, and the Air Infiltration and Ventilation Centre (AIVC) 20th Annual Conference, held Edinburgh, Scotland, 8-13 August 1999, Volume 4, pp 79-80.

A test rig for long-term tests of activated carbon filters was developed consisting of eight parallel test-filter sections. The test-rig was installed on the roof of a six storey commercial building located in the centre of Goteborg, Sweden. By this arrangement, eight activated carbon filters are tested simultaneously under realistic conditions, using the pollutants in the ambient outdoor air as challenge substances.

activated carbon filter

#NO 12302 The combined wind and stack effects on the induced air flow volume in a two-story building through the investigation of wind velocity, solar insulation, and roof design.

Chao N-T, Chiang C-M, Wang W-A

UK, Garston, BRE, 1999, proceedings of Indoor Air 99, the 8th International Conference on Indoor Air Quality and Climate, and the Air Infiltration and Ventilation Centre (AIVC) 20th Annual Conference, held Edinburgh, Scotland, 8-13 August 1999, Volume 4, pp 839-844.

One sixth of the total energy consumed in Taiwan is for building operation, mainly for summer cooling. The energy consumed for summer cooling can be greatly reduced if natural ventilation can be exerted in Taiwanese urban apartments. To explore the feasibility of applying stack ventilation in urban apartments during warm season of Taipei, this study examines the ventilation volume induced by the combined wind and stack effect in a two storey building. The examined parameters are roof design, wind velocity, and solar heat flux. This research is conducted in three-dimensional computational fluid dynamic simulations. It is found that roof type I is able to induce larger ventilation volume when weaker driving forces are considered. Roof type II obtains larger induced air volume when stronger driving forces are considered. In this study, the induced air flow volume ranges from 8 to 14 times of air change per hour. This ventilation volume is much larger than required in a naturally ventilated building when the warm season of Taipei is considered.

stack effect, wind effects, air flow

#NO 12379 Roof ice dams. It's not really a roofing problem.

Sartor J

Canada, Solplan Review, May 1999, pp 6-7.

The winter of 1999 produced many ice dams on shingle roofs in central and eastern Canada. The resulting leaks caused widespread damage to ceilings, walls and interior furnishings of many homes, and served to highlight construction shortcomings. States that the cause is closely linked to heat loss due to low insulation levels at the ceiling edge, proper attic ventilation at this point and warm air leakage from the house below. To correct or prevent the ice dams, the ceiling edge insulation, air leakage and eaves ventilation need attention. Specifies full depth ceiling insulation at the roof edge, full ventilation at every rafter space between the top of the insulation and the roof sheathing, and eliminating interior air leakage especially near the outside wall. 

condensation, roof, attic, cold climate

#NO 12387 Large-scale glass atrium maximises natural energy.

CADDET

Netherlands, CADDET, Result 338, March 1999, 4 pp.

The Sapporo Factory is a large-scale commercial building complex in the heart of snowy Hokkaido. The complex has a large barrel-roof glass atrium with a comfortable indoor environment, which is maintained by making the most of cool outdoor air in summer and sunshine in winter. The atrium also provides a bright indoor space, which is never covered with snow, even in winter. Any snow falling on the glass roof is removed using the natural characteristics of snowfall. Energy consumption records for the atrium indicate that it is extremely energy efficient due to the effective use of natural energy.

atrium, commercial building, cooling, daylighting

#NO 12436 Ventilated solar roof air flow and heat transfer investigation.

Sandberg M, Moshfegh B

Pergamon, Elsevier Science Ltd, 1998, proceedings of "Renewable Energy: Energy Efficiency, Policy and the Environment", World Renewable Energy Congress V, 20-25 September 1998, Florence, Italy, edited by A A M Sayigh, Volume 1, pp 287-292, 4 figs, 3 tabs, refs.

The governing parameters for flows generated by heat transfer from solar cell modules to air gaps as discussed. Experimental results are presented from measurements in mock-ups of ventilated facades and roofs. The heat transmitted from the solar cells to the air have been mimicked by the use of heating foils. The inclination angle of the roof, position of solar cell module and the height to width ratio (aspect ratio) have been varied. The bulk properties as the air flow rate in the air gap, local temperatures and velocities have been measured. Results of importance for design of hybrid systems and cooling of solar cells have been obtained.

active solar, hybrid ventilation

#NO 12438 Defying all skeptics, Steve Lentz's homes work great.

Anon

USA, Energy Design Update, October 1999, pp 6-9.

Describes the work of a home builder who has successfully incorporated airtight techniques in his new homes, without suffering indoor air quality or condensation problems, or prohibitive extra costs. The builder charges $1 extra per square foot for a package of airtightening and insulation measures, which meet the US Energy Star rating. The ten measures taken are: Use 2-inch extruded polystyrene on the exterior basement wall instead of the 1 inch specified in the Wisconsin energy code; Wrap all footings with 3-mil cross-laminated polyethylene instead of ordinary poly; Locate all ductwork inside the envelope (within conditioned spaces) and seal it with silicone mastic; Use 1-inch extruded polystyrene (R-5) under the basement floor versus none; Use 1 inch of polyisocyanurate on the exterior instead of 1 inch of extruded polystyrene; Use R-64 blown cellulose insulation in the attic versus R-38; Use cross-laminated 3-mil polyethylene as your air-vapour barrier instead of ordinary poly; Create a continuous air-sealed envelope; Make the attic hatch tight and well insulated; Install a radon-approved sealed sump pump.

low energy buildings, air tightness, cost effectiveness, energy rating, residential building

#NO 12441 Your mobile home. Energy and repair guide for manufactured housing.

Krigger J

USA, Saturn Resource Management, 1998, 224 pp.

The most important feature of manufactured homes for their customers is their low cost - about one third that of the average site-built home. Many metal-sided and metal-roofed mobile homes from the 1960s and 1970s are still in good repair in the United States. Most older mobile homes can be cost-effectively renovated and weatherized. Manufacturing defects, including ineffective insulation and duct air leakage can cause moisture problems, and inadequate insulation is also a major energy problem, along with excessive air leakage. Some new US mobile homes can be very energy efficient. This book describes how the homeowner can upgrade the energy efficiency of the older mobile home, reducing heating and cooling cost by up to 40%. Covers foundations, landscaping, health matters, air leakage, insulation, floors, walls, doors and windows, roofs and ceilings, heating, cooling, water heating, plumbing and electrical matters.

low income housing, retrofitting

#NO 12444 Insulation tops list of low-income weatherization measures.

Anon

USA, Home Energy, July/August 1999, pp 10-11, 2 tabs.

States that the gas savings from the 1994 Ohio Home Weatherization Program (HWAP) were among the highest that have been documented in any published, large-scale weatherization assistance program evaluation based on actual billing data. Electricity savings were also significant. Attic and wall insulation, along with air sealing, provided the bulk of energy savings. For the 244 gas-heated multifamily units, the average reduction in gas usage following weatherization was 251 ccf per year; for the 2,209 gas-heated single-family homes, the reduction was 324 ccf per year. This represented 23% of total usage and 29% of heating usage for the single-family homes. The 150 electrically heated single-family homes and 116 electrically heated multifamily units averaged a savings of 2,000 kWh per year, which represented 9% of total usage and 17% of heating usage. Floor insulation appeared to provide no significant savings, although many of the units receiving floor insulation were mobile homes. A quarter of the homes received duct sealing measures, but the observed savings were not significant. 

retrofitting, low income housing, energy saving programme

#NO 12497 Improving night ventilation into low-rise buildings in hot-arid climates exploring a combined wall-roof solar chimney.

Aboul Naga M M, Abdrabboh S N

Pergamon, Elsevier Science Ltd, 1998, proceedings of "Renewable Energy: Energy Efficiency, Policy and the Environment", World Renewable Energy Congress V, 20-25 September 1998, Florence, Italy, edited by A A M Sayigh, Volume 3, pp 1469-1472, 5 figs, refs.

A theoretical investigation of a combined wall-roof solar chimney to improve nighttime ventilation in buildings is presented. A spreadsheet computer program is used for the parametric study to find out the optimum configuration of the wall-roof chimney. It has been reported that a roof solar chimney alone can induce an air flow rate 0.81 m3/s when the average incident solar radiation is 850 W/m2. The maximum air velocity induced is 1.1 m/s when the 25 Deg. inclined chimney plates are 0.25m apart. The aim of the paper is to predict the induced air flow as a result of the combined effect and to find the best height. The wall chimney height is varied from 1.95-3.45 m to determine the optimum length in relation to the chimney inlet. The results show that air flow is three times more than that of the roof solar chimney alone (0.81 to 2.3 m3/s). The maximum air flow rate of 2.3 m3/s occurs at 3.45m wall height. ACTION Psychometrics software is used to predict the mean cooling load corresponding to the induced ACH. An air change per hour up to 26 could be achieved for a flat volume (321m3). Such ACH could be utilized to improve night ventilation to reduce indoor air temperature and cool low-rise heavy buildings with large diurnal outdoor temperature variations.

hot climate, dry climate, passive cooling

#NO 12507 Advanced bioclimatic architecture for buildings.

Sala M

Pergamon, Elsevier Science Ltd, 1998, proceedings of "Renewable Energy: Energy Efficiency, Policy and the Environment", World Renewable Energy Congress V, 20-25 September 1998, Florence, Italy, edited by A A M Sayigh, Volume 1, pp 271-276, figs, refs.

The town-planning guide for the areas of the high speed rail station of Florence, is finalised at the synthesis of a comprehensive strategic design of the overall objectives bring out by the town-planning scheme of the city. The new bioclimatic strategies realised for the new buildings involved natural lighting systems, roof developed such green areas, passive solar glazed facades, passive neutral ventilation, underground design strategies.

urban climate, environmental design

#NO 12565 Measured airtightness of an installed skylight.

Shaw C Y, Magee R J, Poirier G F

USA, ASHRAE Transactions, Winter Meeting 2000, Dallas, 6 pp, 7 figs, 1 tab, refs.

An art gallery building had problems with moisture. Inspections using thermographic techniques suggested that air leakage through the skylights could be the main cause of the problem. The air leakage rate of an installed metal frame skylight, 26 m long x 8.5 m wide, was measured, using the balanced fan depressurisation method. Also, fan depressurisation tests were performed on the glazing/upstand interface on the south side of the skylight. The air leakage rates were measured through the full interface and on the west and east halves separately. The methods used for field testing of such components and the test results are discussed.

air tightness, roof, window, public building, moisture, air leakage rate

#NO 12582 Pressure coefficient simulation program.

Knoll B, Phaff J C, de Gids W F

UK, Air Infiltration Review, Vol 17, No 3, June, 1996, pp 1-5, 6 figs, 5 refs.

Airflow and thermal stratifications solutions in a single-zone building with buoyancy-driven ventilation are derived. Two new 'empty air-filling box' models are developed, and it is shown that the fully-mixed model overpredicts the clean zone height and the ventilation airflow rate, while the 'emptying water filling box' model underpredicts the two ventilation parameters. It is also found that the fully mixed model predicts a much lower neutral level height for the building than that predicted by models considering thermal stratification.

A computer program named "Cp Generator" has been developed to predict the wind pressure coefficients, Cp, on the facades and roofs of block shaped buildings. The program is based on fits of measured data, including wind shielding by obstacles and terrain roughness. The main advantages of the program are: it needs no expertise in wind pressures; the input is simple. It exists of building and obstacles coordinates and orientations; generating Cp values for ventilation model calculations needs no separate action. By linking the pressure simulation program and the ventilation calculation program as well as their input, wider application of ventilation programs for non-experts becomes possible. The accuracy of the predicted wind pressures in the first version of the pressure simulation program is promising. Some development is still needed, however, in particular complex building shapes and surroundings have to be dealt with more carefully, as well as increasing wind velocities in small passages. Detailed improvements are also necessary, for example, to account for sloped roofs and the position of ventilation provisions above roof level. Consequently, generation and implementation of additional wind tunnel data is planned, to improve the present version of the program.

wind pressure, ventilation rate

#NO 12592 Low-energy house with photovoltaic power system.

CADDET

Netherlands, Centre for the Analysis and Dissemination of Demonstrated Energy Technologies (CADDET), Result 356, October 1999, 4 pp, 1 fig, 1 tab.

A low energy house built in Kikuyo-machi, Kumamoto, Japan, has been designed with a high level of thermal insulation and is very airtight. The design has reduced the thermal-loss coefficient by 60% compared to a house with standard insulation. A central HVAC system with a heat exchange ventilation unit provides a comfortable environment. A roof mounted photovoltaic (PV) system supplies all the power required for air conditioning and cooking during the daytime under a clear sky. This eliminates the need for gas or oil. The special design of the house saves about 44% of the net energy costs compared with an average house in that area.

active solar power, low energy house

#NO 12627 Beheersing van de verspreiding van uitlaatgassen in de Scraphal van Roba te Ijsselstein. Control of the spread of exhaust gasses in the van Roba scrap hall in Ijsselstein.

Knoll B

Netherlands, TNO-Bouw, 1993, TNO-rapport 93-BBI-R1265, 47 pp, 26 figs, 2 tabs.4 refs, in Dutch.

In the scrap hall of ROBA in IJsselstein non-ferrous materials are processed for re-cycle. The transport of material in the scrap hall is done with lorries and cranes. The exhaust fumes from these vehicles are a hindrance to the employees. In previously carried out research it was established that the health factor should not be excluded, especially with short duration stops with high exhaust fume concentrations. With respect to the average concentrations in the hall the existing ventilation systems was nevertheless unacceptable.

For this reason with the help of a computer system developed by TNO for flow simulation, investigations were carried out and especially the effect of possible measures to be taken for the reduction of the high concentrations in the vicinity.

The most effective measure seems to be the constructing of fourteen mixing ventilators in the hall on the ceiling, with a total air circulation of 20 m3/s. The expectations are that even at peak production levels, the exposure is limited to around the proper health levels for an eight hour exposure.

In doing so the complaints are reduced considerably.

Possible disadvantages are that with the higher air movement the chance of draughts are increased.

To reduce this it is advisable to provide a high/low switch in the circulating system that can be adjusted by the users.

An advantage is that the descending air movement reduces heat loss through the roof.

To reduce the heat loss even further with moderate production circumstances, it is recommended to switch the exhausters up to the production intensity. The switching of this system by random hall users is not recommended.

Increasing the ventilation remains a less effective measure from the point of view of generally high exposure.

Other disadvantages are the necessary extra supply features, possible noise interference to the area and additional heating.

motor vehicle exhaust gas, industrial building, ventilation requirements, occupant reaction, controls

#NO 12628 Ventilatie van de overdekte los- en laadplaats van het PTT-expeditieknooppunt te Haarlem. Ventilation of the covered loading and unloading bay of the PTT shipping terminal in Haarlem.

Knoll B, Phaff J C

Netherlands, TNO-Bouw, 1982, Rapport C 506, 8 figs, 2 tabs, 5 refs, in Dutch.

The new still to be established expedition junction of the Post Office in Haarlem consists of an indoor discharging- and loading-berth. The transporting is taken care of by different types of vehicles. The exhaust fumes from these vehicles cause pollution in the inhaling air. To reduce the concentration of pollution to an acceptable level it is apparent that in a peak in the transport a fresh air system is required which meets a ventilation rate of 12 per hour. In the original design it appears that during unfavourable weather conditions with natural ventilation via the outlets only a ventilation size of 6,4 per hour arises. This follows calculations with a sum model for the ventilation. From additional calculations it appears that there are a few possibilities to increase the ventilation: enlargement of the roof gaps to net 300 m2 width of passage; enlargement of the wall gaps with net 430 m2 width of passage; installing mechanical ventilation of approximately 65 m3/s. A combination of these possibilities can also be chosen.

For which design will eventually be chosen depends on the architectural possibilities, the consequences for the noise inconvenience to the area and the installation and company costs.

This choice will ultimately be taken by the architectural agency and consultation with the Post Office. Herein the weather climate should be taken into consideration for the users of the building. That is why this report also contains the influence of the ventilation system on the indoor environment. 

large building, motor vehicle exhaust gas, air change rate, natural ventilation, weather

#NO 12632 Onderzoek inzake de ventilatie van de parkeergarage in het woning- en winkelcomplex aan de Dijkstraat te Zwolle. Investigation regarding the ventilation of the parking garage in the dwelling and shopping complex at Dijkstraat in Zwolle.

Kornaat W

Netherlands, TNO-Bouw, 1993, TNO-rapport 93-BBI-R0355, 30 pp, 6 figs, 1 tab, 7 apps, in Dutch.

At the request of Schutte Building company in Zwolle (contact person Mr. G.R. Bos), research was carried out by the department of Indoor Environment Building Physics and Systems of TNO Building and construction research, concerning the ventilation of a parking garage at cellar level in the (still to be built) housing and shopping complex in the Dijkstraat in Zwolle.

The architectural execution of these parking garages is such, that it does not comply with the rules and regulations that are mentioned in NPR 2443 for naturally ventilated parking garages [1]. The purpose of this research is to establish if possible natural ventilation can be achieved and if there is sufficient ventilation and adequate outlets for the produced carbon monoxide.

The natural ventilation was therefore examined with the TNO Building and Construction Research ventilation calculating model, while in a number of other cases the internal air movement pattern and the concentration distribution is defined with the computer programme WISH 3D.

It is established that the necessary ventilation (fresh outdoor supply) is approximately 1m3/s.

Consideration is taken of a maximum stopping time in the parking garage of 15 minutes. In a situation without additional provisions a similar level is only reached with wind speeds of 5m/s, which is inadequate. Bearing in mind that the required ventilation must be able to be maintained by wind speeds from 1 m/s. Lower wind speeds only happen about 5% of the time. In the framework of this research, the possibility of very low ventilation occurring in combination with a peak load is sufficiently restricted.

The placing of ventilation provisions in the west front is not recommended, because of the possibility of hindrance from high pollution levels on the frontage. This forms an important restriction with the design.

By applying additional provisions in the ceiling of the parking garage, constructed to emerge from between the housing blocks (see configuration B, table 1), the required ventilation level can be maintained. The through flow of the westerly half of the parking garage is then inadequate.

A proper through flow is possible if: the entrance/exit is changed and emerges from the south-west corner of the parking garage; a "round pump" ventilator is attached for the internal mixing. An output of 0,5 m3/s is sufficient, if the air is moved from the easterly to the westerly half of the parking garage. Approximately 10% of the time a similar type of ventilator must be turned on; a shaft emerging at roof level (no hindrance by co-emission) is applied for the ventilation of the south west corner (see configuration C, table 1). However this requires drastic architectural changes.

The required ventilation and through flow can also be achieved by the application of mechanical air supply for the western half.

Insufficient through flow from the westerly half of the parking garage, could possibly be caused by screens because the storage area and the staircase are beside the entrance/exit area. Recommendations are: to find out to what extent these screens can be reduced by architectural adjustment; and to carry out additional research (especially to the internal through flow) to establish if by carrying out these adjustments there is sufficient natural ventilation in the parking garage.

Recommendation is that after the completion of the complex CO-measurements are done, to examine the design.

parking garage, shopping mall, natural ventilation, carbon monoxide

#NO 12633 Evaluatie van het ventilatiesysteem van de los- en laadruimte van het PTT-expeditieknooppunt te Utrecht. Evaluation of the ventilation system of the loading and unloading bay of the PTT shipping terminal at Utrecht.

Knoll B

Netherlands, TNO-Bouw, 1992, TNO-rapport B-92-1087, 30 pp, 1 fig, 2 tabs, in Dutch.

In the closed discharging- and loading-berth of the PTT-expedition junction in Utrecht, the employees have experienced hindrance from exhaust fumes. Especially at the beginning of this year the number of complaints were high.

Since the start the number of traffic activities has increased. In this context the emerging exposures have been measured and the function of the CO-detection system and of the ventilating system have been critically looked into.

The exposures of different components in the exhaust fumes appeared to remain under the accepted limits. 

This was also the case with the carcinogene component benzo(a)pyrene.

Even so the concentrations of this component appear to overstep the target value for the outside air. Therefore taking measures for further reduction is recommended. 

Although the short peak concentrations are acceptable from the health point of view, they are considered responsible for the apparent complaints. 

The large number of complaints in the beginning of this year is presumably caused by closed air inlets in the facade.

The CO-detection system appears to be less accurate with low concentrations. 

With high concentrations the exposure of employees are systematically over estimated. 

Therefore a responsible position of the measuring points should be nearer to the riding hole.

By the cyclic scanning of the measuring points the signal of the CO-detector can change, without any change of the local concentrations in the room. To obviate this a switch off-delay of at least one measuring cycle is recommended.

The action levels of the CO-detector have in principle been adjusted too high.

A reduction in the switching-point of the front and roof ventilation to the MAC-value of 25 ppm is recommended.

For the alarm value a decrease to the 15 minutes limit-value of 120 ppm is recommended.

It has to be established if decreasing the action levels the accuracy of the sensor is still sufficient.

Switching the room ventilation system to short time general peak concentrations is not useful. That is why a switching slowing-down of 5 to 10 minutes is recommended, in combination with a similar integration time of the detector signal. By application of signal-integration a further reduction of the switching level is recommended to anticipate on generally raised concentrations.

The ventilation appears to amount to a diversion in the measurements of about 3 per hour. This coincides with the specification of the ventilation system.

The spatial ventilation is considered to be sufficient. There are no disturbances established in the present ventilation system. 

To improve regulating the general diffusion of exhaust fumes, improvement in the general ventilation or a screening on the edge of the car park and the driving zone is recommended.

Some options for the general flow chart control are: displacement flow with the help of steering air supply from the car park to the driving zone; air-curtain-like screenings between the car park and the driving zone, located at the edge; air-showers located at the working place of the employees.

As an alternative an airtight as possible dividing wall can be applied, possibly provided with car sluices with bushes. To control the through flow from openings the following has to be taken care of: overflow of air by sufficient under pressure in the driving zone with respect to the car park; air-curtains.

motor vehicle exhaust gas, large building, occupant reaction

#NO 12684 Unventing attics in cold climates.

Lstiburek J

USA, Home Energy, November/December 1999, pp 27-28, 2 figs.

Explores the possibility of constructing a cold climate attic with no vents, and achieving large improvements in performance and energy savings. Venting can cause problems in cold dry climates such as allowing snow to blow in, as well as problems with the design of complex geometry roofs. If the roof sheathing is kept above the dew point temperature of the interior air vapor mix, condensation and moisture accumulation will not occur. So the ventless design will depend on installing a continuous ceiling vapour diffusion retarder/air retarder and thick ceiling insulation. 

attic, cold climate, sealing, moisture

#NO 12716 Impact of ASHRAE Standard 62-1989 on Florida retail stores.

Chasar D A, Shirey D B

in: USA, ASHRAE, 1999, "IAQ and Energy 98: Using ASHRAE Standards 62 and 90.1", pp 99-113, 6 figs, 9 tabs, refs.

Increased outdoor air ventilation rates will greatly increase dehumidification loads to be met by air-conditioning (AC) systems in most humid climate applications. In this study, building energy simulation software was used to investigate the impacts of increased ventilation as specified by ASHRAE Standard 62-1989 on a typical Florida retail store. Detailed evaluation of indoor humidity was accomplished through modelling of moisture transport and storage in common building materials. In addition, a model to predict the effect of continuous supply fan operation on air-conditioner latent capacity was included.

Annual simulations of the modelled retail store were performed using hourly weather data for Miami, Orlando and Jacksonville. Heating, ventilating and air-conditioning (HVAC) system performance was evaluated and compared for a conventional direct expansion (DX) system as well as several commercially available alternative technologies. Cost-effective options for meeting the new ventilation requirements were identified through analysis of the installed first cost and life-cycle cost for each system.

Simulation results indicate that conventional rooftop package DX air conditioners with a sensible hear ration (SHR) of 0.75 would be made unable to maintain acceptable indoor humidity throughout the year under the new ventilation standard. While elevated ventilation rates increase both sensible and latent loads on HVAC systems, the ventilation load can be over 90% latent in humid climates. Several of the alternative HVAC systems evaluated in this study were able to offset the increased ventilation loads, including the heat pipe-assisted air conditioner, chilled water system with ice storage, and three pre-treatment technologies in conjunction with a conventional air conditioner (100% outside air DX unit, gas-fired desiccant system, and enthalpy wheel). While all of these systems provided enhanced humidity control, the enthalpy recovery wheel system did so while minimizing the energy impacts of increased ventilation. In addition, the enthalpy wheel system offered the lowest first cost and life-cycle cost of any of the other alternative technologies. 

standard, commercial building, humidity

#NO 12775 Ventilation impact of a solar chimney on indoor temperature fluctuation and air change in a school building.

Khedari J, Boonsri B, Hirunlabh J

Energy and Buildings, No 32, 2000, pp 89-93, 9 figs, 2 tabs, 10 refs.

The aim of this research was to investigate, experimentally, both the feasibility of a solar chimney to reduce heat gain in a house by inducing natural ventilation and he effect of openings (door, window and inlet of solar chimney) on the ventilation rate. The study was conducted using a single-room school house of approximately 25m3 volume. The southern wall was composed of three different solar chimney configurations of 2 m2 each, whereas, the roof southern side included two similar units of 1.5 m2 each of another solar chimney configuration. Those configurations were built by using common construction materials. Experimental observations indicated that when the solar chimney ventilation system was in use, room temperature was near that of the ambient air, indicating a good ability of the solar chimney to reduce house's heat gain and ensuring thermal comfort. The air change rate varied between 8 - 15. Opening the window and door is less efficient than using solar chimneys, as temperatures between room and ambient was higher than that obtained with solar chimneys. 

natural ventilation, school building, tropical region, field testing, thermal comfort

#NO 12789 Ventilation in 2 or 3 unit multifamily buildings before and after weatherization.

Gerbasi D

Canada Mortgage and Housing Corporation, December 1999, 29 pp + app,., 11 refs.

This study investigates the fresh air distribution in 2 or 3-unit multifamily buildings before and after weatherization and evaluates the effectiveness of exhaust-only ventilation in providing the minimum recommended fresh air flows to dwelling s in such buildings. Low-rise multifamily buildings often have no mechanical ventilation system and rely on the air leakage through the exterior envelope to provide outdoor air to occupants. Weatherization of the roof space, a common energy conservation measure applied to 2 or 3-unit multifamily buildings (also known as Duplex or Triplex) in Quebec can greatly reduce the equivalent leakage area of the exterior shell and change the location of the neutral pressure plane. Consequently, this has major impact on the outdoor air supply to the building and how it is distributed on a unit-per-unit basis. Field test data characterizing the shell leakage and inter-zonal leakage of a case study building was used to define various pre-and post-weatherization airflow models. Airflow models were introduced in CONTAM a software developed by the National Institute of Standards and Technology (NIST). To determine the air change profiles (fresh air change & total air change) for the individual dwellings. The results of simulations presented herein shed light on the most popular mechanical ventilation strategy used in weatherized low-rise multifamily buildings. 

retrofitting, apartment building, air distribution

#NO 12792 The parameters of the ventilation system of uninsulated cow shed.

Kavolelis B

Energy and Buildings, No 32, 2000, pp 1-4, 2 figs, 1 tab, 3 refs.

According to the equations of the balances of heat and moisture, the experimental and the analytical data, the mathematical model is created to ground the temperature regime and to calculate the parameters of the ventilation system of the uninsulated cow shed and that with the insulated roof. The suggested countable difference of the value between the internal and external temperatures is 3oC, the greatest permitted meaning is 6oC, and is does not depend on the other parameters of the building in the damp climate zone (in winter, the average dampness of the air is 85%), when the heat transmission coefficient of the external barriers of the cow shed is k = 3.0 W /(m2K). When the roof is insulated (kr + 0.3 W / (m2K)), the countable value of the temperature differences rises up to 7 - 11oC. 

animal house, temperature difference, openings

#NO 12865 Ryomintatilan ratkaisut ja rakennusfysiikka. Kosteustekninen suunnittelu. Crawl space types and building physics.

Matilainen M, Jerkku I, Kurnitski J

Finland, Helsinki University of Technology, Laboratory of Heating, Ventilating and Air Conditioning, Report B63, Espoo 1999, 61 pp, in Finnish.

Different types of crawl spaces are listed and their physical behaviour including heat, moisture and air change is discussed. The objective was to collect information on the behaviour of crawl spaces, especially concerning moisture control and optimum air change. In addition, the results of two other reports are given in the form of preliminary guidelines for crawl spaces. The behaviour of ordinary crawl spaces ventilated naturally or mechanically by outdoor air as well as heated crawl spaces, unventilated crawl spaces and crawl spaces ventilated by indoor air are discussed. Preliminary guidelines are given for crawl spaces ventilated by outdoor air. Ground moisture evaporation and the crawl space temperature are the most critical factors affecting the moisture behaviour of a crawl space. If the ground moisture evaporation is not reduced by ground cover, the humidity of the crawl space will rise over the limits of mould growth. Properties of ground cover and calculation methods to assess moisture evaporation are given. Air change will affect both humidity and temperature in crawl space. The need for air change is discussed based on results from previous and the present research and some guidelines for optimum ventilation are given. The given guidelines are specific and include the control of roof-, surface- and ground water as a part of crawl space design. The guidelines are preliminary and will be revised in the second stage of the project. Publishing of preliminary guidelines is considered to be useful, as even a small improvement of the current situation might be a notable step ahead towards properly functioning crawl spaces.

crawl space, guidelines, ventilation strategy

#NO 12881 Field measurements of performance of roof solar collector.

Khedari J, Mansirisub W, Chaima S, et al

Energy and Buildings, No 31, 2000, pp 171-178, 13 figs, 11 refs.

To reduce the mechanical cooling cost of new housing built in a hot and humid region, the design should maximize the natural ventilation and minimize the fraction of sun energy absorbed by a dwelling. This objective is accomplished by using the roof structure to act as a solar collector. The roof solar collector design (RSC) used CPAC Monier concrete tiles and gypsum board. Two units of RSC were integrated in the roof structure of the school solar house. The effects of air gap and openings of RSC on the induced air flow rate and thermal com fort were studied experimentally.

solar collector, field monitoring, natural ventilation, openings

#NO 12892 Candid canon.

Field J

UK, Building Services Journal, June 2000, pp 18-22.

Describes Canon's new headquarters, which departs from the usual air conditioned head offices of major corporations. Taking full advantage of its site, the naturally ventilated building features narrow-plan office spaces with exposed concrete ceilings and restful atria. Overheating is reduced by daytime cross-ventilation and automatic night ventilation. The presence of lux detectors should provide effective control of office lighting. The building has one of the UK's largest photovoltaic roof cladding installations.

natural ventilation, case study, office building, atrium

#NO 12908 Comparison of Windows and DOS versions of the DOE2 in simulating a passive building.

Nutalaya S, Givoni B, Schiler M, Labib T

in: PLEA '99 "Sustaining the Future - Energy, Ecology, Architecture", proceedings of a conference held Brisbane, Australia, September 22-24, 1999, edited by Steven V Szokolay, published by PLEA International, in conjunction with the Department of Architecture, The University of Queensland, Brisbane, Volume 2, pp 603-608, 6 figs, 1 tab, refs.

Visual DOE is a Windows interface version of the DOE2 simulation program. Its purpose is to help save time in writing BDL input for the simulation. As its calculation engine is the same as DOE2 in the DOS version, DOE should result in the same output as the DOS version. However, difficulties arise in identifying the building's con figurations, materials and construction and systems in the two input versions. While modelling a simple one-storey "passive" building, it was difficult to get a good match in the simulation results in the two versions. Furthermore, using the Windows version of DOE is not as simple as it should be. For example, it was harder to model a simple "pitched" roof using the Windows version than in the DOS version. Similar problems with shading devices is the difficulty in modelling the configuration of the shading, resulting in errors in calculating the correct solar gain. As a result, it is necessary for the Windows users to create an input file, run the program to generate a BDL file, freeze the BDL manually, and then run again using the modified BDL.

Even after such modifications, the match between DOS and the Windows versions of DOE-2 was not consistent. Comparing the simulations of the two versions with measured data, when the buildings were closed and un-shaded, show better a match with the Windows version. On the other hand, when the same buildings were shaded, the Windows version showed a poorer match with the measured data. In simulation sequences of days with varying climatic conditions, the Visual DOE's output was lower than the DOS output on some days and higher on other days. 

building performance, simulation, calculation techniques

#NO 12921 Torre Guil environmental educational centre, Murcia, Spain. Proposal for energy saving and demonstration.

Blanco I, Casanovas A J

in: PLEA '99 "Sustaining the Future - Energy, Ecology, Architecture", proceedings of a conference held Brisbane, Australia, September 22-24, 1999, edited by Steven V Szokolay, published by PLEA International, in conjunction with the Department of Architecture, The University of Queensland, Brisbane, Volume 1, pp 59-64, 5 figs, 1 tab, refs.

The buildings of this Environment Educational Center, designed with innovative energy saving features, minimize the impact on the preexisting environment. Renewable energy concepts have been applied to the building design, and intelligent control of lighting and air-conditioning has been included. Most of the buildings are green roof underground buildings, where domes that allow spans up to 42 m have been designed. Average energy saving is over 70% on heating and cooling demands and 60% in lighting. The design optimize the energy savings on underground constructions through several innovative concepts as the use of specific natural materials that act both as insulators and thermal mass or the selective distribution of the thermal mass on building perimeter. The Center will promote the demonstration of rational use of energy and disseminate on environmental protection. The studie of the view was made to integrate architecture and surrounding. From our point of view, "it is necessary to gain knowledge and to cultivate lectures of natural environments from all points of view, including the architect who must be able to adopt a posture of respect towards nature, even when this means you are unable to leave your artistic print at the building site". 

energy efficiency, renewable energy, building design

#NO 12934 A "new" approach to passive design for residential buildings in a tropical climate.

Soebarto V I

in: PLEA '99 "Sustaining the Future - Energy, Ecology, Architecture", proceedings of a conference held Brisbane, Australia, September 22-24, 1999, edited by Steven V Szokolay, published by PLEA International, in conjunction with the Department of Architecture, The University of Queensland, Brisbane, Volume 1, pp 369-374, 5 figs, refs.

The typical passive design suggested for residential buildings in tropical hot-humid climates is a lightweight building with many openings on the north and south walls to allow continuous natural ventilation, shaded by wide overhangs. In reality most people no longer favour this design approach for several reasons: building durability, noise problems, privacy, and social status. The work presented in this paper challenges the typical design suggestions and shows other alternatives that are more suitable for this climatic region. The use of massive construction, which is a common practice in Asia, is tested. Other investigations include examining the effects of using radiant barriers and roof insulation, changing the building orientation and shading conditions, and using various floor an roof claddings. The results demonstrate that the default approach of using lightweight, continuously ventilated structures, is not necessarily the most climate-responsive for this climatic region. Also. The use of radiant barriers provides the most significant improvement in cimatic region. Also, the use of the radiant barriers provides the most significant improvement in the indoor thermal comfort. 

passive design, tropical climate, residential building

#NO 12941 Roof design for natural cooling.

Yannas S

in: PLEA '99 "Sustaining the Future - Energy, Ecology, Architecture", proceedings of a conference held Brisbane, Australia, September 22-24, 1999, edited by Steven V Szokolay, published by PLEA International, in conjunction with the Department of Architecture, The University of Queensland, Brisbane, Volume 1, pp 427-434, 5 figs, ref.

A recent European project explored combinations of radiative and evaporative cooling processes involving the roof for application in the Mediterranean region. The paper introduces the experimental applications which were built and tested as part of the project and the design considerations and applicability data from simulation models validated with the experimental results.

roof, building design, cooling, natural ventilation

#NO 13006 Insulating an attic access.

Anon

USA, Home Energy, March/April 2000, pp 10-11.

Guidelines for insulating an attic hatch.

attic, openings, air sealing, residential building

#NO 13026 Ventilation and IAQ for the hospitality industry.

Turner W A

Heating Piping and Air Conditioning, July 2000, pp 36-44, 8 refs.

Designers of HVAC systems for the hospitality industry are faced with the challenge of providing suitable indoor environments for both an establishment's customers and its workers at an affordable price. This involves consideration of first and operational costs, system maintainability, and degree of environmental control, which includes: temperature control; interior moisture management; pollutant control; interzonal pressure control and the influence of adjoining facilities. This article explores these environmental control challenges and discusses ways to meet them. Concludes that many advanced ventilation designs can address most, if not all, of the environmental challenges described. It is especially important to implement these designs inclimates that are hot and humid, very cold, or both, which can be found throughout much of the continental United States. In many ways, the environmental challenges found in the hospitality industry are no greater than those found in health care facilities and semiconductor manufacturing. However, in general, HVAC capital equipment and operational costs are expected to be lower in hospitality industry applications than in either of the other tow types of applications. All of the advanced solutions noted here require an investment in capital equipment beyond packaged, off the shelf rooftop units; however, in most cases, the costs canbe recovered in a relatively short period of time. It would be useful for ASHRAE to develop more information regarding these advanced equipment approaches. This expanded section on the control of tobacco smoke emissions as a point source or mobile point source in the American Conference of Governmental Industrial Hygienists' Industrial Ventilation: A Manual of Recommended Practice' would help designers to more unformly address these issues.States that until sufficient educational material is available, the development of advanced solutions that work well will depend on the talents of engineers and designers who create them through research efforts.

duct, maintenance, residential building

#NO 13029 Hygrothermal performance of attics.

Samuelson I

J. Thermal Env. & Bldg. Sci, Vol 22, October 1998, pp 132-146, 9 figs, 2 tabs, refs.

This paper describes the results of measurements of temperature and relative humidity in six different attics (roof spaces) under controlled conditions. All six attics have the same dimensions and have been constructed adjacent to each other in a single line, but with different insulating materials and ventialted in different ways. Using this fund of measured data, a number of researchers have attempted to apply their mathematical models and, starting from the basis of measured ambient climatic conditions, have calculated expected values of temperature, relative humidity, and in one case, the moisture ratio in the attics. The results of these calculations showed difficulties in matching the performance of the models to real conditions. Notes that there is some degree of moisture buffering in hygroscopic insulation materials (cellulose materials) compared with non hygroscopic insulation (mineral wool). However, the difference is not particularly large; there are considerable differences in moisture and temperature variations in roofs with high and low ventilation rates. The higher the amount of ventilation using outdoor air, the greater the variations; The climate in the attic becomes drier the less it is ventilated. States that moisture can be introduced during the building stage or in normal use. Building moisture must be allowed to dry out before it can cause damage. During the subsequent use stage, convection of moist air up into the attic must be prevented. This is done by ensuring that the structure is airtight in combination with an internal negative pressure.

attic, moisture

#NO 13041 Static split duct roof ventilators.

Gage S A, Graham J M R

UK, Building Research and Information, Vol 28, No 4, 2000, pp 234-244, 10 figs, 1 tab, refs.

Split-duct roof ventilators or windcatchers are used to provide both supply and extract ventilation to the spaces which they serve. However, building are often erected in conditions where there is no prevailing wind direction. An investigation into four and six segment windcatchers to determine their relative performances under different wind conditions was undertaken using scale models in a wind tunnel. Conclusions indicate that six segment windcatchers have a more predictable, reliable performance in uncertain or variable wind conditions. However, a four segment windcatcher that is orientated 45 degrees to the prevailing wind will generate the highest pressure differences and consequently the highest duct speeds in an installation. Further work on strategies for windless conditions are summarised, and scope for further research is indicated.

natural ventilation, ventilators, ducts, wind effects, alternative technology, wind tunnel

#NO 13044 Designs on learning.

Anon

UK, Energy and Environmental Management, July/August 2000, pp 28-29.

Discusses whether the optimum energy efficient design can be achieved within standard UK school building costs. States that it can. States that a well designed, comfortable school is not only conducive to efficient learning but also provides the opportunity to reinforce the sustainability message to learners. Describes Weobley Primary School in Leominster and Notley Green County Primary School in Essex. The former is fuelled by locally produced wood chips. The architecture is classic passive solar design using cross ventilaton and optimising use of natural daylight. A central courtyard further assists daylight and natural ventilation. There is also shading to minimise summertime heat gain. The building also utilises a 'breathing wall' system. For the second school, the client asked the design team to explore ideas which could be adapted on other projects while working within Essex Primary School Model Brief and the standard Essex budget for new school buildings. They are interested in how sustainability extends beyond construction into the use and management of the building. Features include an energy efficient plan shape; a 'breathing wall' uses recycled newspaper as insulation; masonry internal wall s will contribute to the thermal mass required to avoid summer overheating; daylighting is provided by a combination of perimeter windows and clerestory lights, and rooflights; natural ventilation and gas condensing boilers, and zoned underfloor heating.

school, sustainability, passive solar design

#NO 13088 Experimental testing of a ventilated roof component for energy saving in cooling.

Dimoudi A, Androutsopoulos A, Lykoudis S

UK, Air Infiltration and Ventilation Centre, proceedings of "Innovations in Ventilation Technology", 21st AIVC Annual Conference, held The Hague, Netherlands, 26-29 September 2000, paper 39.

A Ventilated roof component was built and tested in the outdoor testing facilities (Test Cells) of CRES, Greece. A conventional Greek roof structure of the same area was also installed in the roof of the Test Cell allowing simultaneous measurements in order to perform a comparative study of the performance of the two parts. Different configurations in the Ventilated roof were investigated, like ventilation air gap height and application of a radiant barrier. The tests carried out under summer weather conditions will be discussed in this paper. The experimental results showed a better performance of the Ventilated roof compared to a conventional roof construction under summer climatic conditions.

roof, cooling, test cell

#NO 13111 Thermal performance of the exterior envelopes of buildings VII proceedings.

Geshwiler M (ed.)

USA, Atlanta, American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), 1998, proceedings of a conference held Sheraton Sand Key Hotel, Clearwater Beach, Florida, 6-10 December 1998, 874 pp.

The papers of this conference are divided into subject areas as follows: roofs and attics - principles; whole building performance; moisture analysis - principles; whole building performance - practices; moisture assessments - principles; indoor air quality and sustainability - practices; moisture surveys - principles; walls - practices; window design and performance - practices; roof and attic issues - heat, moisture, ventilation - practices; window modelling at the University of Massachusetts - principles; moisture - practices; thermal analysis of building systems - principles; fenestration and energy costs - practices; wall systems - principles; infiltration - practices; building systems - principles; performance of air barrier systems - practices; airtightness and airflow in buildings - principles; materials and foundations - practices.

thermal performance, building envelope

#NO 13112 Application of a new type of air and vapour retarder in a self drying dloped roof with a cathedral ceiling.

Hens H, Janssens A

USA, Atlanta, American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), 1998, proceedings of "Thermal performance of the exterior envelopes of buildings VII" a conference held Sheraton Sand Key Hotel, Clearwater Beach, Florida, 6-10 December 1998, pp 15-27, 8 figs, 8 tabs, refs.

In cool and cold climates, sloped roofs with cathedral ceilings are quite sensitive to moisture damages caused by built in moisture and prolonged concealed condensaton of water vapour produced inside. Conventional solutions are to leave a cavity between the thermal insulation and the sheathing and vent it with outdside air and/or to include a vapour barrier below the insulation layer. An alternative, however is the self-drying roof. This concept was evaluated experimentally. For that purpose, three well insulated roof sections, all covered with shingles and lined inside with a gypsum board, were tested in a hot box. The first had an airflow and vapour tight polyethylene film between the glass fibre insulation and the gypsum board internal lining. The second had the gypsum board only as an airflow retarder, and the third has a new type of organic, glass fibre fabric reinforced felt as airflow and vapour retarder. The plywood deck under the shingles contained a known amount of built in moisture. The sections were exposed to a sunny period first, followed by a steady state cold period afterwards. Section I remained wet, with the moisture moving from the plywood to the polyethylene during the sunny period and back to the plywood during the cold period. Section 2 dried during the sunny period; however, it got less than roof 2. Apparently, roof 3 came closest to the concept of self-drying. In order to evaluate to what extent simple engineering tools and simplified models could predict the measured response, the tests were also simulated using three such models.

air barrier, vapour retarder, roof, cold climate

#NO 13113 Convective processes in loose fill attic insulation - metering equipment.

Wahlgren P

USA, Atlanta, American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), 1998, proceedings of "Thermal performance of the exterior envelopes of buildings VII" a conference held Sheraton Sand Key Hotel, Clearwater Beach, Florida, 6-10 December 1998, pp 55-64, 9 figs, refs.

A large scale model of an attic construction has been built in a climatic chamber. The purpose of the attic test model is to investigate heat transfer - in particular, heat transfer by convection - in loose fill attic insulaton. The influence of a number of factors on heat flows can be investigated using the attic test model; for example, insulation thickness, attic ventilation, ceiling construction, roof slopes, and the quality of installation workmanship. The heat flow through the attic ceiling construction is measured with a metering box. The design and calibration of the metering box is described in detail in this paper. During calibration of the metering box, the thermal conductivity of the calibration board was determined within 0.6% of that determined at the Swedish National Testing and Research Institute, SP. Computer simulations carried out to help design the attic test model and to predict the function of the metering box are presented. The location of convection cells in the loose fill insulato will be determined by investigating the temperature variations on the surface of the insulation by using thermocouples and an infrared camera. The preliminary test program for the attic test model is also presented.

attic, loose fill insulation, scale model, test chamber, heat transfer

#NO 13123 Condensation risk assessment.

Janssens A, Hens H

USA, Atlanta, American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), 1998, proceedings of "Thermal performance of the exterior envelopes of buildings VII" a conference held Sheraton Sand Key Hotel, Clearwater Beach, Florida, 6-10 December 1998, pp 199-206, 8 figs, 7 tabs, refs.

The methodology of risk analysis and assessments is reviewed and applied to study the reliability of condensation control measures in lightweight building envelopes. It is generally recognized that airtight construction is an essential part of condensation control. Nowadays, different air barrier systems are developed and documented to prevent air leakage and moisture accumulation in the envelope. But does this mean that the condensation risk is sufficiently minimized and that the protective system is reliable? Considering the high occurrence of human error in the building process, the possibility of air barrier defects during the service life of a building envelope may be high.

To define the reliability of the condensation control system, the consequences of air barrier failure are quantified using a two-dimensional numeric control volume model for the calculation of combined heat, air, and vapor transfer in multi-layered building envelope parts. A set of failure modes and design calculation conditions is defined for an exemplary wood frame insulated roof, and a failure effect analysis is performed in order to predict the condensation risk as well as a result of air barrier defects. The effectiveness of redundant design measures to improve the reliability of the condensation control system is studied.

condensation, building envelope, air tightness, model

#NO 13130 Case study - ice dam remediation for Northeast ski area condominiums.

Fennell H C

USA, Atlanta, American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), 1998, proceedings of "Thermal performance of the exterior envelopes of buildings VII" a conference held Sheraton Sand Key Hotel, Clearwater Beach, Florida, 6-10 December 1998, pp 445-463, 11 figs, refs.

This is a case study describing the procedures for locating, prioritizing and repairing the causes of ice dam formation at a complex of over one hundred Northeast ski-area condominiums. The testing, performed on four typical units, as commissioned by the Owner's Association to prove the feasibility of preventing ice dam formation without replacing all of the existing roofs and to determine the costs of this approach. 

Ice dam formation is one of the predominate problems for building in cold climates. The causes for such formations are often misunderstood by building owners and construction industry professionals alike. Consequently, because the heat-loss sources usually cannot be visually detected, solutions to the problem are more apt to be attempts at limiting damage from the symptoms rather than preventing damage to the building by eliminating the root causes of the ice dams. In addition to roof leaks, hazards from falling ice and potential structural damage to the building are additional reasons to prevent ice formation rather than just addressing leakage. Systems for limiting damage and preventing the intrusion of water from ice dams into the building envelope can be successful but are often more expensive and do not improve the energy performance of the structures. Eliminating the actual causes of ice dams i.e., excessive warming of the roof surfaces in subfreezing weather, always saves energy. This case study looks at a complex of buildings where it was possible to utilize conservation measures to remediate ice dams. It is broad in the scope of its examples because these multi-family buildings with their complicated construction details included many warm air leakage and conductive heat loss problems that have led to ice formation during extreme winter conditions.

condensation, eaves, cold climate, roof

#NO 13131 Moisture in the roofs of cold storage buildings.

Tobiasson W N, Greatorex A R, Fabian B A

USA, Atlanta, American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), 1998, proceedings of "Thermal performance of the exterior envelopes of buildings VII" a conference held Sheraton Sand Key Hotel, Clearwater Beach, Florida, 6-10 December 1998, pp 465-467, 2 figs, refs.

The low-slope on roofs of ten cold storage buildings in the Dallas area visually and thermographically (Tobiasson and Korhonen 1985) from above and below. Two inch (51mm) diameter cores were taken to verify infrared findings and to determine moisture contents for estimating wet thermal resistance (Tobiasson et al. 1991). Twelve inch (0.3 m) square specimens of much of the insulation was removed for laboratory studies of their thermal properties and structure. Types of Insulation encountered included fibrous glass, fiberboard, perlite, woodfiber, expanded and extruded polystyrene, isocyanurate, and phenolic. Six of the ten roofs had suffered problems and had new single-ply membranes. Of the six, all but one has insulation added above their old bituminous membranes.

Visually, all ten roofs appeared to be in good condition. However, areas of wet insulation were found in eight of them. Some moisture was associated with infiltration of warm, moist outdoor air at roof-wall intersections without effective air seals. Figure 1 shows photographic and thermographic images taken within a freezer of a corner suffering such problems. Frost has formed there as warm moist outdoor air infiltrated into the freezer. The bright portion of the thermogram is the area warmed by infiltrating air. The adverse effects of air infiltration on the thermal performance of freezer roofs deserves further study. Of all the insulation examined, permeable fibrous glass was the most susceptible to wetting by air infiltration. While fibrous glass insulation may be able to be dried out (by warming up freezers), the rapidity at which cancers of wet insulation can grow in it make it somewhat ill-suited for use in freezers and coolers where vapor drive and air movement are both usually inward. Some wetness was due to leaks caused by flaws in the roofing membranes and their flashings. Figure 2 shows photographic and thermographic images of a ballasted roof that contained wet phenolic insulation due to and inch (25 mm) long cup in the EPDM rubber roofing membrane there. The phenolic insulation has lost almost all of its insulating ability and thus the surface of the roof appeared colder (darker) in the thermogram than does the roof of surrounding area where the phenolic insulation was dry and effective.

Nighttime on-the-roof infrared moisture surveys were more valuable than daytime indoor infrared surveys, but the indoor surveys and indoor visual inspections helped define the nature and extent of the moisture problems in these roofs.

Since the undersides of these roofs do not contain deliberate vapor retarders, it may be possible to recover some of the insulating ability lost to wetting of fibrous glass insulation by warming each freezer for a few days to allow ice to melt and the meltwater to drain our of the roof at seams in the decks. However, the other insulations cannot be dried this way since they take much longer to dry. Thus, a cost-effective, easy, reliable way of drying most of the wet insulation in these roofs is not available. Flaws in the new single-ply membranes caused wetting of new expanded polystyrene insulation placed between the old bituminous membrane and the new single-ply membrane. Unfortunately there is no way to dry such "trapped" insulation. One roof with a steel deck contained several areas of wet phenolic insulation. Had that deck not been cold, the wet phenolic probably would have rusted through. Being cold, the rate of rusting has been quite slow, but a safety hazard is developing there. As long as a roof membrane and its flashings keep water and moist air away from the insulation in the roofs of cold storage buildings, almost any insulation will stay dry and perform well. However, sustained one-way vapor drive, the sealing-in of moisture at the base of insulation in roofs of freezers by freezing, and the limited opportunities for wet insulation in such roofs. Provide incentives to use insulation that is very resistant to wetting. Its very low rate of moisture gain by vapor diffusion and its resistance to wetting in the presence of freeze-thaw cycles (Tobiasson et al. 1997) makes extrude polystyrene insulation particularly appealing for the use in the roofs of freezers and coolers. The Cold Regions Research and Engineering Laboratory (CRREL) Special Report 98-13 "Moisture in the Roofs of Cold Storage Buildings" documents the details of this study. Copies are available from CRREL, 72 Lyme Road, Hanover, NH 03755-1290

moisture, roof, insulation, air infiltration, air sealing, cold store

#NO 13147 The pressure response of buildings.

Lstiburek J W

USA, Atlanta, American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), 1998, proceedings of "Thermal performance of the exterior envelopes of buildings VII" a conference held Sheraton Sand Key Hotel, Clearwater Beach, Florida, 6-10 December 1998, pp 799-817, 21 figs, refs.

Airflow in buildings is one of the major factors that governs the interaction of the building structure with the mechanical system, climate, and occupants. If the airflow at any point within a building or building assembly can be determined or predicted, the temperature and moisture (hygrothermal and psychometric) conditions can also be determined or predicted. If the hygrothermal conditions of the building or building assembly are known, the performance of materials can also be determined or predicted. This paper shows that airflow in buildings is complex, time dependant and multidirectional. The understanding of airflow through and within buildings has been based on the requirement for continuity of mass and momentum caused by wind forces, thermal effects (stack action), and forces associated with the operation of mechanical cooling, heating, exhaust and other ventilation systems.

Interstitial airflow and interstitial air pressure fields are not often considered. Building analysis typically develops the building pressure field from the airflow field. In doing so, exterior and interior walls, floors, and roof assemblies are either considered as monolithic or having openings resulting in flow across the specific assemblies. 

This paper shows that many problems associated with pollutant transfer and the spread of smoke and fire cannot be explained by cross-assembly (one-dimensional) airflow as well as such moisture effects as microbial contamination, corrosion and biological decay. Even the analysis of energy consumption and comfort within buildings needs to be considered in terms of multidirectional airflow. This paper shows that buildings typically comprise multi-layer envelope assemblies with numerous air gaps or void spaces that are often connected to service chases. Complex three-dimensional flow paths and intricate air pressure relationships must be considered. 

This paper also introduces an alternative pattern of analysis: developing the flow field, the leakage areas, and the flow relationships from the measured building pressure field - the air pressure regime within and surrounding the building. This approach accounts for interstitial air pressure fields and resulting interstitial airflows. It provides a powerful diagnosis tool for solving many of the problems related to direct and indirect effects of airflows.

air flow

#NO 13152 Greenhouse for tropical butterflies and sport palace Sicily.

Nicoletti M

UK, Pergamon, 2000, proceeding of "Renewable Energy. Renewables: The Energy for the 21st Century. World Renewable Energy Congress VI", edited by A A M Sayigh, held 1-7 July 2000, Brighton, UK, Part 1, pp 51-56, 4 figs.

Tropical butterflies can not be housed in air conditioned spaces. To reproduce the climate conditions of the tropical forest, at the Zoological Institute of the University of Catania a special multifaceted greenhouse was designed as to keep constant in the day and through out the seasons the natural solar heat gained. 

In the tensi-structural of the sport palace of palermo, the shadowing of the fully glazed opposite ends of the building is controlled by two spectacular array of 27m long stainless steel pipes describing two different warped shapes in space. They also are functional to carry off the rain water collected by the 60m span, 100m long concave roof whose intrados by a laminar air flow naturally activated.

sports building, hot climate, animal house, passive solar design


 


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