AIVC, Air Infiltration Review, Volume 20, No 4, September 1999

Edinburgh Hosts a Popular 20th AIVC Annual Conference

by Malcolm Orme, AIVC

This year the 20th Annual AIVC Conference was held between 9th to 13th August, 1999, in conjunction with Indoor Air 99 at the Edinburgh International Convention Centre in Scotland. Indoor Air 99 itself covered all aspects of the indoor environment, with the AIVC sessions concentrating on areas of particular relevance to building ventilation. In particular these were:
  • energy,
  • guidelines, operation and comfort,
  • modelling and simulation,
  • systems and strategies,
  • air cleaning and filtration,
  • natural ventilation, and
  • components.


A total of 730 papers and posters were presented at Indoor Air 99, in both plenary and parallel sessions. From these, 140 were presented in the AIVC sessions. A selection of AIVC papers from the Conference are described below.

Plenary Sessions

Two AIVC papers were presented during plenary sessions. The first, presented by Martin Liddament (AIVC, UK) reviewed the purpose of ventilation and the quality of ventilation air. In his presentation, he stated that ventilation is the process by which 'clean' outdoor air is intentionally provided to a space and 'stale' air is removed. In an occupied space, its fundamental purpose is to provide oxygen for metabolism and for the dilution of unavoidable pollutants. However, too often it falls upon ventilation to accomplish tasks for which it is not appropriate. For example, pollutant source control is a better strategy than dilution and removal by additional ventilation. Furthermore, the quality of ventilation air may be affected by:

  • outdoor air quality,
  • the siting of air intakes,
  • active control of intake air,
  • filtration, and
  • cleanliness of the ventilation system.

The second AIVC plenary paper described a survey that has been conducted across 7 European countries. This survey concerned current design methods for ventilation systems in residential and commercial buildings and was part of the EU TIPVENT project. Discussing the results, Åke Blomsterberg (J&W Consulting Engineers, Sweden) indicated that traditional design methods seldom involve advanced calculations. Instead, the preferred methods are simple calculations, rules of thumb, manufacturers' design programs and catalogues and may involve many different handbooks and guidelines. For these reasons, innovative, low energy ventilation systems are seldom introduced.

Selected Papers from the AIVC Sessions

The influence of nocturnal ventilation reduction on daytime indoor air quality has been investigated by Lars Gunnarsen (Danish Building Research Institute, Denmark). (An untrained panel of 45 people assessed the air quality in terms of acceptability.) He suggested two effects may lead to a deterioration of air quality. The first is caused by pollutants being absorbed at night and then re-emitted during the day. The second is due to the slower removal of pollutants at the reduced average ventilation rates. He concluded that if ventilation is stopped for 12 hours every night, then the daytime rate may need to be more than doubled to compensate.

Giorgio Giorgiantoni (ENEA, Italy) has used a detailed description of a typical modern Italian dwelling, with airtightness characteristics determined from blower door tests, to produce a prediction of the IAQ in the dwelling. The ventilation air flows were simulated using the multi-zone model CONTAM96, which was additionally used to calculate the time-dependent concentrations of 3 cooking-generated pollutants. This study represents part of a larger investigation into the characteristics of the Italian dwelling stock in terms of energy use and IAQ (indoor air quality).

In a paper presented on behalf of the authors Mark Bassett and P Gibson, the findings from measurements made in 12 naturally ventilated New Zealand schools were explained. It was found that the wintertime ventilation rates (estimated from changes in carbon dioxide levels over time) were substantially higher than the estimated air infiltration rates alone. However, the average rates were not quite as high as 8 litres per second per person, the value stated in New Zealand Standard NZS 4303 for mechanical systems.

Ultraviolet germicidal irradiation (UVGI) may be used for air disinfection, and therefore to reduce the number of hospital originating infections. This is becoming increasingly critical as the number of drug resistant micro-organisms increases. Clive Beggs (University of Leeds, UK) has undertaken optimisation of a UVGI system in a UK hospital building. He explained how lower air velocities in a system, together with the face area presented to the ultraviolet source, allow greater irradiation doses to be applied to micro-organisms in the air.

Oil is used for corrosion protection for new galvanised sheet metal HVAC components, during storage and transport. However, if this layer remains after installation, it may increase dust accumulation and also serve as a potential growth media for microbes. Pertti Pasanen (University of Kuopio, Finland) gave an account of the development of methods to measure the level of contamination of oil, so that manufacturers are able to check for remaining residues. The 'filter contact' technique was found to give the best recovery of oil from surfaces and the repeatability was good.

In his presentation, Ornulf Kristiansen (NTNU, Norway) explained how an inspection of a representative number of HVAC plants in Trondheim, Norway, has revealed that snow and sometimes rain are easily able to pass through their air intake louvers. This ingress of moisture, which may lead to unwanted microbial growth, was observed in almost all of the systems.
In cold climates, the supply air through vents in mechanical exhaust ventilated buildings may be excessively cold. A way of reducing the draught from such supply vents is to use preheating. In an experimental study of a particular design of supply vent for displacement ventilation incorporating preheating, Elisabeth Mundt (KTH, Sweden) found that for them to operate as intended, a large under-pressure and an airtight building are needed.

Low temperature heating (LTH) systems are those that use, for example, residual, ambient, or renewable sources of heat. Herman Eijdems (Cauberg-Huygen, The Netherlands) discussed the impact of these systems on IAQ, thermal comfort and energy use. He concluded that LTH systems can provide good thermal comfort if they are used in buildings with a high level of insulation and an airtight construction. The IAQ is also positively influenced, with a reduction in dust mites and suspended particles, as well as less stuffiness and odours, because of the lower air temperature.

At the Conference, Klaus Fitzner (Technical University Berlin, Germany) explained his experiments to investigate the influence of air flow patterns in a room on evaporation and humidity distribution around a simulated person. (He has achieved this with a heated wet cylinder to represent a human body.) His work compared the surface temperatures and humidities for mixed and displacement flow. In fact, he demonstrated that the evaporation of water from a heated, wet surface is 20% higher in mixed flow than displacement flow.

The combined control of natural and mechanical ventilation using 'fuzzy' control algorithms was the subject of a contribution by Gordon Sutherland (University of Athens, Greece). In his system, the indoor CO2 level is taken to be the controlled parameter for IAQ. The conflicts between the IAQ control strategy and the control of thermal and visual comfort are resolved through intelligent compensation and adjustment of, e.g. the indoor air velocity and solar control devices.

Best AIVC Paper and Best AIVC Poster

The Best AIVC Paper at the Conference was awarded to Bill Nazaroff (University of California at Berkeley, USA) for his paper, "Particle deposition from turbulent duct flow". In his account of his work, he described a comparison between three theoretical models of particle deposition in rough-walled ducts and also experimental data. He found that all three models predicted particle penetration through an entire ventilation system would be independent of particle size for particle diameters less than 2 micrometers. However, the predicted results between the models differed considerably.

Anne-Marie Bernard (CETIAT, France) won the Best AIVC Poster, for her poster, "Energy loss due to ventilation: impact of average values and simplifications on calculations". In this poster, she explained how simplification of input data for calculations of the energy loss due to ventilation may affect the results. Particularly significant, she determined, are building airtightness, meteorological and site conditions, as well as wind pressure coefficients.

References

  • Liddament 3,1-6 (AIVC #12,421)
  • Blomsterberg 4, 7-12 (AIVC #12,422)
  • Gunnarsen 1,1-6 (AIVC #12,185)
  • Giorgiantoni 1, 708-713 (AIVC #12,216)
  • Bassett 4, 298-303 (AIVC #12,284)
  • Beggs 2, 659-664 (AIVC #12,260)
  • Pasanen 5, 19-24 (AIVC #12,312)
  • Kristiansen 4, 55-60 (AIVC #12,277)
  • Mundt 5, 45-50 (AIVC #12,317)
  • Eijdems 1, 7-12 (AIVC #12,186)
  • Fitzner 1, 732-737 (AIVC #12,220)
  • Sutherland 1, 367-372 (AIVC #12,208)
  • Nazaroff 2, 24-29 (AIVC #12,231)
  • Bernard 1, 76-77 (AIVC #12,198)

 

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