Foam Insulation
As far as Tom Silva is concerned, low-density polyurethane spray foam is the insulation technology to beat. 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. While spray foam is expensive, its installation costs are offset in the long run by lower heating and cooling costs.
Insulating Cathedral Ceilings
When Tom insulates a cathedral ceiling or a finished attic, he also turns to foam. Sprayed against the underside of the roof deck, it seals against air movement, eliminating the need for a vapor barrier or ventilation. But its open-cell structure still allows moisture to escape.
