![]() ![]() ![]() In most climates, it needs a vapor barrier. Like other batt-type insulation, fiberglass has a predictable R-value if not compressed but is difficult to fit around obstacles without leaving gaps. Illustration by Ian Worpole Fiberglass Insulationįiberglass batts, the insulation found in most houses in the U.S., are inexpensive and quick to install. But its open-cell structure still allows moisture to escape. Sprayed against the underside of the roof deck, it seals against air movement, eliminating the need for a vapor barrier or ventilation. When Tom insulates a cathedral ceiling or a finished attic, he also turns to foam. While spray foam is expensive, its installation costs are offset in the long run by lower heating and cooling costs. Consider its advantages: It forms a lock-tight bond with studs and sheathing that blocks all air movement, it flexes enough to accommodate seasonal wood movement, and it retards (but doesn't halt) moisture passage. In fact, a bad job can actually make matters worse.Īs far as Tom Silva is concerned, low-density polyurethane spray foam is the insulation technology to beat. Its effectiveness at resisting this movement is called its R-value the higher the value, the lower your energy bills.īut to achieve its rated R-value, insulation must be installed correctly. Whether it's thick blankets of fiberglass batts, meringue like mounds of spray foam (Tom's favorite), or layers of seaweed (discovered under the floors of the first TOH project), all insulation works the same way: by trapping tiny air pockets that slow the movement of heat out of a house in winter and into a house in summer. "A well-insulated house will make you more comfortable in every season. "It's the wisest way to invest that I know of," he says. When it comes to insulation, says This Old House general contractor Tom Silva, money truly can buy happiness. ![]()
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