Unfortunately, fiberglass, which is most commonly used, allows air to readily pass through it, significantly dropping the manufacturer's listed R-value for the insulation. The new Massachusetts building codes are requiring that builders address this issue by demanding that fiberglass in walls be sealed with an air barrier on all six sides (front, back, both sides, top and bottom). Some towns, such as Newburyport, that have signed up with the Green Communities Act have adopted the stretch code; it requires an overall house depressurization test (easily performed by a home performance contractor using a blower door fan) to achieve a certain level of air-tightness in new construction.
There is beginning to be a shift away from hiring an insulation contractor, who usually just brings your home a one-size-fits-all sweater to hiring a home performance contractor who has the ability to test and analyze and then make your home perform efficiently. With the application of an air barrier and the right insulation, a building performance contractor — soon to be a familiar term — can best ensure comfort, safety, house durability and, yes, energy savings.
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Tim Gould is director of Energy Egghead (www.EnergyEgghead.com), an Amesbury-based home improvement company that provides thorough energy audit and conservation services.