Ventilation Introduction Air movement through a building is the main element of passive cooling in many Australian climates as the moving air cools the occupants through increasing evaporation rates. It is the least expensive means of cooling a building and the lowest environmental impact. Air movement within a building may be uncontrolled or accidental and is referred to as infiltration, or may be deliberate via natural ventilation through doors, windows and other openings. It may also be due to forced ventilation provided by extractor fans or simply ceiling or wall fans moving air within a room. Air movement provides useful cooling in all climates but may be less effective in tropical climates during periods of high humidity. Modelling Air Movement Infiltration Infiltration is the uncontrolled airflow that occurs through gaps, cracks, wall and ceiling vents that are unable to be closed and flues without dampers. Infiltration is detrimental to thermal performance in all climates, although performance in winter is much more sensitive to drafts than in summer. The building’s occupants require a minimum flow rate of half an air change per hour that changes oxygen and expels carbon dioxide and water vapour. Larger infiltration rates may be required where the indoor air quality is poor due to the out gassing of surface finishes, carpets, plastics etc. Infiltration can be reduced via the following means: Draught sealing doors and windows and caulking gaps and cracks is low cost, and particularly worthwhile on windy sites. Enclosing the under floor space of timber houses is effective in reducing drafts. Dampers should be fitted to all or chimneys. Strategic planting around the house can reduce the speed of the winter winds, and reduce the resulting heat loss through infiltration. The diagram below shows some possible infiltration sites.
Ventilation Introduction Air movement through a building is the main element of passive cooling in many Australian climates as the moving air cools the occupants through increasing evaporation rates. It is the least expensive means of cooling a building and the lowest environmental impact. Air movement within a building may be uncontrolled or accidental and is referred to as infiltration, or may be deliberate via natural ventilation through doors, windows and other openings. It may also be due to forced ventilation provided by extractor fans or simply ceiling or wall fans moving air within a room. Air movement provides useful cooling in all climates but may be less effective in tropical climates during periods of high humidity. Modelling Air Movement Infiltration Infiltration is the uncontrolled airflow that occurs through gaps, cracks, wall and ceiling vents that are unable to be closed and flues without dampers. Infiltration is detrimental to thermal performance in all climates, although performance in winter is much more sensitive to drafts than in summer. The building’s occupants require a minimum flow rate of half an air change per hour that changes oxygen and expels carbon dioxide and water vapour. Larger infiltration rates may be required where the indoor air quality is poor due to the out gassing of surface finishes, carpets, plastics etc. Infiltration can be reduced via the following means: Draught sealing doors and windows and caulking gaps and cracks is low cost, and particularly worthwhile on windy sites. Enclosing the under floor space of timber houses is effective in reducing drafts. Dampers should be fitted to all or chimneys. Strategic planting around the house can reduce the speed of the winter winds, and reduce the resulting heat loss through infiltration. The diagram below shows some possible infiltration sites.
ThermLearnGdC9.docx