Wall air leakage speaks to what is wall air leakage, why wall air leakage and type of wall air leakage.
It is air moving through a building assembly wherever air pressure differences exist between one side of the assembly and the other.
These pressure differences can be created in a number of ways.
By wind forces acting on the external surfaces of a building.
By stack effect, which is the tendency of tall buildings to act somewhat like chimneys, drawing air in at either the top or bottom and expelling at the other end. This stack effect may be decreased or eliminated if a proper air balance is done for the building. If the air systems return air is set that equal air is returned from the lower floors as the upper floors stack effect may be greatly reduced.
Correct minimum air volumes with carbon dioxide control as an overriding factor should be done. This may be accomplished by correctly setting the air systems mixed air controls for building mechanical systems equipment such as air handling systems and exhaust fans.
When outside air infiltrates a building through exterior walls and roofs, it increases building energy consumption. A recent study, in the year 2005, by the US National Institute of Standards and Technology estimated that air infiltration can account for as much as 40 percent of a building’s heating, cooling and ventilating costs.
This infiltration is worse when the building is operated a negative inside building pressure as compared to outside.
Outside air infiltration also introduces unfiltered air pollutants and unfiltered air into the building’s interior, where it can compromise indoor air quality and reduce occupant comfort. Air leakage transports water vapour into insulated walls and roofs, increasing the risk of condensation and moisture damage to building components.
When air leaks between spaces within a building, it can disrupt pressure differentials maintained by heating, ventilating and air conditioning systems (HVAC) for the purpose of controlling the spread of odours or contaminants between separately zoned sections of the building.
For example, unpleasant cooking odours can be drawn from one apartment building living unit to another, car exhaust or carbon monoxide fumes from a parking garage can infiltrate adjacent occupied areas, dust particles can be carried into a laboratory clean room or bacteria may be introduced into a hospital operating suite.