A.Michael Uniacke, owner of Advanced Insulation in Prescott, Ariz., replies: When it comes to insulation, quality control is at least as important as the choice of materials and methods. If all the work is done carefully, you can effectively insulate a floor over a cold space using fiberglass batts. But the more plumbing, wiring, central vacuum pipes, and the like that run through the floor, the harder it is to achieve a careful fit and the more I'm inclined to use a blown-in or sprayed-in product. I'd rather rely less on hand labor and more on a mechanical process that has some measure of inherent quality control.

A critical detail like this also needs good coordination between the builder, the insulator, and the other subcontractors (especially the plumber). The big worry is the potential for pipes to freeze. If plumbing runs within the floor system, it's vital to have the plumber hold the piping as close to the subfloor as possible, away from the cold,...

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