AIVC - Air Infiltration and Ventilation Centre

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Wind loads on low-rise buildings-effects of roof geometry.

Describes measurement of wind pressures on low-rise buildings at Aylesbury. Pressures were recorded simultaneously at over one hundred positions divided between seven houses in an estate and a specially constructed building situated on open ground adjoining the state. The roof pitch of the experimental building could be quickly varied to any angle between 5 and 45 deg. and this was used to investigate the variation of pressure distributions over the surfaces of the building. Data are presented for two skew wind directions. Initial comparisons are made with wind-tunnel tests.

Measurements of ventilation rates in houses with natural and mechanical ventilation systems

Describes measurements made to compare ventilation rates in six Belgian houses with both natural and mechanical ventilation systems using O2 and N2O as tracer gases. Ventilation rates were correlated with wind speed. Air leakage across individual components of the house was measured and from this the distribution of leakage areas calculated.

A tracer gas method for the continuous monitoring of ventilation rates.

Describes how ventilation rates in two houses with recirculating air distribution systems were monitored by injecting CO2 tracer gas into the supply and measuring its concentration in the return air. In one house with solid concrete floor, normal windows and air bricks, ventilation rates were mainly dependent on wind speed. In the other with suspended timber floor and weatherstripped windows ventilation rates were much lower and mainly dependent on internal to external temperature difference.

The prediction of ventilation rates in houses and the implications for energy conservation

Developes mathematical model of air infiltration based on crack flow equations. Describes measurements made on test house. Shows that actual pressure distributions in walls deviate considerably from values in guidebooks. Finds background leakage area of house by pressurizing house with electric fan and measuring pressures. Suggests two distributions for leakage areas. Measures infiltration rate using helium tracer gas, recording temperature and pressure differences. Concludes that comparison between prediction and experimental results is encouraging.

Ventilation research in occupied houses

Gives results of measurements of air-change rates and heat loss in occupied and unoccupied houses on two sites, one exposed and the other sheltered. Observations of the wind pressures on the houses and of the window-opening habit of the occupants are discussed. These are used in conjunction with the results of a regional survey of the temperatures maintained and the window-opening habits in local authority houses to extend the application of the results of other housing.

Determination of the ventilation rate in a series of social houses

Describes the determination of infiltration rates for houses in Seneffe. Gives infiltration rates for individual rooms, found using O2 as tracer gas, and recording wind speed and direction. Determines global air renewal rate using N2O as tracer gas, by injecting gas through ventilators into all rooms and measuring concentration in each room. Calculates global concentration from individual measurements.

Comparison of measured and computer-predicted thermal performance of a four bedroom wood-frame townhouse.

Measurements of the dynamic heat transfer in a four-bedroom townhouse were made under controlled conditions in a large environmental chamber to explore the viability of a computer program developed at N.B.S. labelled NBSLD for predicting heating and cooling loads and inside temperatures. Test house was factory-produced, of modular design and lightweight (wood) construction. Tests were performed with simulated outside summer, winter and autumn diurnal temperature cycles. Inside temperature was maintained at 75 f and the activities of a six-member family were simulated.

Approaches to evaluation of air infiltration energy losses in buildings.

Outlines parameters governing air infiltration. Discusses problem areas of house to house comparisons of air leakage. Deals primarily with tracer gas procedure as compared with pressurisation/depressurisation approach. Describes testing in townhouses of recent construction as well as in a number of older homes of varied design. Uses roof-top laboratory test chamber to examine relations between wind effects, buoyancy effects and building openings and how they effect air infiltration. Uses results to clarify evaluation of air infiltration.

Estimating air infiltration into houses: an analytical approach.

There is at present no analytical step-by-step procedure for calculating air infiltration into houses. Extracts useful house air infiltration data from almost 20 years of scattered research work. 1) Highlights important conclusions of these papers andgives some selected notes on the many variables involved. 2) Reduces this information and summarises it in 2 tables. sets out 2 worked problems using these tables to demonstrate their application.

The effect of insulation, mode of operation and air leakage on the energy demand of dwellings in the U.K.

Describes results of computer study of behaviour of 2 better insulated houses, one of rationalised traditional and one of timber frame construction. Compares their performance with a contemporary house. Provides most important results regarding mode of operation and effects of air leakage. Concludes that better insulation is effective energy conservation measure but heavyweight characteristic of insulated structures result in intermittent heating being a less attractive means of reducing heat demand. Air leakage, if not controlled, becomes animportant component of the total heat loss.

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