PR1995

A study was set up to compare the effectiveness of passive stack ventilators (PSV) with mechanical extract fans (MEF) in providing adequate ventilation in UK homes. New build and refurbished homes with PSV and MEF were identified and questionnaires posted to 3000 households of which 1223 were returned. The survey showed that in homes installed with a PSV system, only 7% of those in the kitchen and only 8% of those in the bathroom were reported as blocked up. There were also few cases in which the MEF was blocked up or disconnected: 1.5% in kitchens and about 5% in bathrooms.

This paper describes the new indoor environment research facility recently constructed at the Institute for Research in Construction, National Research Council Canada. This facility allows full-scale testing and physical modelling of office space lighting, thermal comfort, indoor air quality, airflow and contaminant-flow patterns, ventilation, acoustical characteristics, and occupants' reactions to these parameters. The facility consists of a test room, approximately, 12 m by 7 m by 2.74 m high, with adjustable interior partitions.

So as to better understand and predict IAQ problems, the velocity field and distribution of local mean age of air were determined experimentally with three-dimensional anemometry and decaymode tracer gas measurements inside a classroom. We also performed 3-D numerical simulations of the velocity field in this room, using a CFD code. The time dependent concentration decay of tracer gas was simulated using the previously determined flow field in the pollutant transport equation. Relatively good agreement was found between the simulated and experimental concentration decay curves.

Disadvantages and advantages with different heating and ventilation systems in modern housing have been discussed during many years in Sweden. The discussion has intensified for modem low energy houses, where the use of forced air heating has increased during the last fifteen years, mostly in one-family houses. In many articles and the general debate diverging opinions have been presented concerning the thermal comfort, the air quality, the ventilation and the energy use in modern one-family houses with forced air heating.

Nowadays it is rather common with demand controlled ventilation in public buildings and offices. The purpose of demand controlled ventilation is to adapt the ventilation to the varying needs of the occupations. In dwellings it is rather unusual with demand controlled system. The main reason for that is the high investment cost for the system. The outdoor air used for ventilation in dwellings is therefore not effectively used. For example in a mechanical exhaust ventilation system 50 % of outdoor air is leaving the house without being used of the people.

The installation of packaged heat recovery ventilation (HRV) systems has recently become common practise in new homes in Canada. Despite improvements in product quality and reliability, HRV systems are only capable of providing safe, continuous, efficient and effective ventilation if homeholders have a understanding of the basic operation and maintenance procedures and the system's interaction with other house systems. Furthermore, homeholders must be able to perceive the value of HRV systems if they are expected to operate them.

The work concentrated on estimating the effects of building leakages and terrain parameters on the air infiltration. The analysis was performed mainly using a multi zone airflow model Movecomp with which the building and its ventilation system could be described in detail. The computations were performed for a flat in a 418-storey building. The highest infiltration occurred in an untight two-facade flat in open terrain. The calculations gave valuable information on the effect of the location of the leakage.

ASHRAE has developed a draft of a measurement standard, Standard 129, entitled "Standard Method of Measuring Air Cliange Effectiveness." This standard defines a method of measurement for measuring air change effectiveness in mechanically ventilated spaces, and provides a discussion of how the values of air change effectiveness may be used to demonstrate compliance with ASHRAE 62-1 989.

The use of IR detectors to steer the ventilation is in principle an attractive approach for optimising the ventilation according to the occupants needs. In order to evaluate the performances under real conditions, one of the BBRI office buildings in Limelette (some 31 offices with in total 51 persons and a variable occupation load) was equipped with a mechanical supply ventilation system in which each terminal is controlled by an IR detector.

The IEA Annex 27, "Evaluation and Demonstration of Domestic Ventilation Systems" is aiming at developing tools by using the most developed computer models and equations available including modul development. Before staring up all the simulations an in depth review of the variables influencing the evaluation of a ventilation system have been done and a report is to be published. All parameters are needed to be mapped so that realistic assumptions can be made for the simulation phase.