In the March/April Issue of Spray Foam Insulation & Roofing Magazine, we discussed how recent changes in the 2009 & 2012 International Energy Conservation Code (IECC) affected the construction of building envelopes. In the process of doing so, we asserted the building code mantra “build tight, ventilate right.” While the previous article focused more on the former part of the phrase, this article focuses on the latter: the proper sizing of HVAC systems. By and large, we will be discussing this in the context of residences.
The Old Way vs. The New Way
For decades, it was commonplace in the building industry to construct houses in such a manner that they would “breathe,” which is to say, “leak.” When the “build tight” paradigm started to emerge, it was sometimes thought a home that could breathe was equivalent to a tightly-built and ventilated home. This is simply not the case. “A leaky home depends on random holes, in random places, and wind and temperature differences to make the air move into and out of the home. It only works occasionally and when it does it’s purely by chance,” said Doug Garrett, Owner of Building Performance & Comfort, Inc. and author of the white paper that inspired this series of articles (found in Resources on 43).