Fiberglass Insulation

Fiberglass batts, the insulation found in most houses in the U.S., are inexpensive and quick to install. Like other batt-type insulation, fiberglass has a predictable R-value if not compressed but is difficult to fit around obstacles without leaving gaps. In most climates, it needs a vapor barrier. Some builders rely on batts with attached kraft-paper facing to do that job, but Tom recommends unfaced batts, covered in plastic with all the seams taped shut.


Batts in the Rafters
Simply jamming batts between the rafters of a cathedral ceiling or insulated attic will interfere with the roof's ability to breathe. The resulting buildup of moisture can soak the insulation (nullifying its R-value), foster the growth of mold, or even rot the framing. The illustration above shows how Tom Silva maintains adequate ventilation and avoids those problems.



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