Leakage and Infiltration
A cornerstone of energy efficient buildings, in both new and renovated existing homes, is having tight envelopes and effective air distribution systems. Leaky buildings waste energy spent on space conditioning as the conditioned air can escape. However, once you have built a tight building, well-controlled fresh air needs to be brought into the house and distributed uniformly within a home. There are a number of short term tests that are used to quantify the air tightness of a home and duct system and to determine the distribution of outside air.
The blower door and duct pressurization tests use similar equipment to pressurize or depressurize the whole house or the duct system, respectively, to measure leakage. The flow rate of air required to maintain a certain pressure can be used to characterize the total leakage area of the house or the duct system. Tracer gas tests provide a more accurate test method, and use the decaying concentration of a harmless gas to calculate ventilation rates.