Noel's Green (make that SUSTAINABLE) Blog

I just love this subject. Do you know whether your building is sucking or blowing? Did you know that even a new building, built to the usual building methods, will leak air? In a new project, the key is to make allowance for that, and design, build and validate accordingly. On an existing building, it is important to determine how much and where your building blows or sucks, so you can take action, if need be. Windows, doors, and construction joints all have a normal tendency to leak air or allow infiltration. Varying pressures within the building and across each envelope, causes air to move through these openings.

“Blower door” tests are a key tool for determining how much leakage occurs and in which direction, in (negative pressure) or out (positive pressure).

The major issues surrounding air leakage are indoor air quality, compromised comfort due to drafts or uneven temperatures, and energy usage. A good HVAC designer will account for all of these, and assure that undesirable effects, such as sucking cold or hot-humid in through the building joints is prevented. Likewise, a good architect/builder will account for the behavior of the envelope assembly, air leakage being but one behavior, in his/her design. (You can’t have a 100% tight envelope in practice, it rather more expensive to achieve 0% infiltration, so we plan for it, and plan to blow rather than suck. This rule does NOT apply to “clean rooms”, of course, where 0% infiltration is mandated.)

Blower door testing is a key component of new building commissioning or re-commissioning an existing building. If you know where all the intakes, exhausts, and door openings are, and their size and type, and then the remainder (theoretically) is the “tightness of the building’s construction”.
Continue reading Building Air Leakage and Air