, Newburyport, MA

December 20, 2011

Finding your thermal weaknesses

Tim Gould

Homeowners may want to consider that addressing their home's comfort issues or attempting to save on heating costs may not be a matter of simply calling an insulation contractor.

Unfortunately, however, there is still a whole lot of insulation being installed that is less effective than it should be. For example, fiberglass batts are still being installed on attic floors without any prior air sealing that would stop warm air from entering the attic from lower floors; also, insulation is being installed without eave baffles that would stop cold air from flowing into the insulation, thereby significantly lowering its R-value.

In order for a home environment to be as comfortable as possible and be energy efficient, a house's overall performance should be examined, usually by a home performance contractor. This involves looking at the house as an interactive system and having an eye for "thermal bypasses," or thermally weak areas. It seems simple, but it is often challenging to look at the alignment of an air barrier and a thermal barrier, which is critical in terms of energy effectiveness.

A good analogy to having your home's barriers in place is to think of a person wearing just a sweater while inside. The sweater keeps him or her warm. However, when going outside, a slight wind will penetrate the sweater, making the person feel cold immediately. A thin windbreaker over the sweater stops air movement and allows the sweater to perform as it should to keep the person warm. Remember, too, that the windbreaker typically completely covers the sweater. It has a drawstring around the waist and fits closely around the neck. A house needs to be effectively insulated the same way with continuous and complete alignment of an air barrier (windbreaker) and a thermal barrier (sweater).

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 (, an Amesbury-based home improvement company that provides thorough energy audit and conservation services.