Some Factors Influencing Thermal Comfort and Air Quality in Residential Buildings. Field Measurements and Laboratory Tests

Doctoral thesis, 1996

The main prerequisite for applying a specific ventilation system in residential buildings is that the demands set upon the indoor air quality and thermal climate can be satisfied. If this cannot be guaranteed using a simple exhaust system, a system with treated supply air, i.e. balanced ventilation, should be considered. From the viewpoint of air quality, the location of the air intakes is important, while the location and design of air inlet devices is significant for achieving an acceptable thermal comfort in a building. The aim of this thesis is to contribute to the knowledge about the factors that should be considered. The thesis is based on both field and full-scale laboratory tests which are presented in eight papers. Since the results are based mainly on measurements, the monitoring procedure and evaluating tools have been thoroughly analyzed. The results presented show that a balanced ventilation system is usually preferable when a building is located adjacent to streets with heavy traffic. It is also shown that investigations of air quality have to be carried out over quite a long period of time, so that the influence of various sources can be charted. Measuring equipment based on photoacoustic spectroscopy is useful for this type of studies. The interference from methane when determining the total concentration of volatile organic hydrocarbons is sometimes regarded as a problem. However, some of the measurement series carried out indicate that it is possible to eliminate this influence. The measurements also show a clear correlation between the concentrations of different traffic related contaminants. The critical part of a room from the viewpoint of thermal comfort is often the near-zone of an air inlet device. If the demands on thermal comfort are fulfilled here, the thermal climate is often acceptable in the rest of the occupation zone as well. The occupation zone should include the whole room volume, except the zones close to inlet air devices, near windows and outer walls and above head height. It is shown that air supply via the slot devices studied, can not be regarded as an acceptable solution especially at low outdoor temperatures, while air supply via a radiator air device can be acceptable if the radiator is warm. The thermal comfort in a room should be characterized mainly by individual parameters and indices not including clothing insulation or activity level. The results presented in this thesis also show that consideration should be taken to the inaccuracy of the measuring equipment when evaluating the thermal comfort. An instrument with a time constant larger than 0.5 s (90%) can be too slow to allow correct recording of the air velocity fluctuations. In addition, demands on the time constant of air temperature sensors may be set since temperature fluctuations up to 3°C can exist in ventilated rooms. The upper frequency of those fluctuations is mainly found in the range 0.2 to 1.2 Hz.