Architect Peter Pfeiffer traces the genesis of his radiant-barrier roof design back to the early 1980s, when spray foam was gaining popularity. “When we were first thinking about applications for spray foam, adding it to attics was a radical change agent for the construction industry,” he recalls.
As a young architect, he felt ventilating attics to keep them cool made little sense because the major heat source was solar radiation, which he reasoned should be prevented from entering the attic in the first place. “Trying to fight radiation with convection, which is what venting is, is a weak strategy from a physics standpoint,” he explains.
Bad attic details waste energy
Peter determined that air leakage was No.1 on the list of reasons for excessive energy usage. Consider that most air conditioners are set up to suck air out of the house, cool and dehumidify it, and send it through a network of ducts back into the house. When ducts are not airtight, they leak, and a good percentage of that conditioned air never makes it into the home. The house then “goes negative,” meaning it takes 100% of the air out to condition it but doesn’t return all of it, which creates negative air pressure. That forces the house to suck makeup air from every crack and crevice. The result can be a 20% or greater energy loss. The process also brings hot, humid air into the house, which the air conditioner then needs to handle.
The knowledge of this energy loss led to efforts on Peter’s part to make duct-blaster tests a code requirement, which would ensure conditioned air is not lost outside the envelope. But even sealed ducts can be less effective if they are located in an unconditioned attic. Peter envisioned not only sealed ducts but also a…
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