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Technical Bulletins

Technical Information / Technical Bulletins

Technical Bulletin 18

Mold and Performance of Wet Insulation

When insulation becomes saturated with water, it will temporarily lose a substantial measure of its thermal resistance (R-value). The spaces of air between the fibers are now occupied by water instead of air, and since water is a much better conductor of heat than air, its presence will cause the insulation to have reduced thermal performance. This is a temporary situation; as soon as the water evaporates and the insulation becomes dry again, it will regain its original performance levels providing it has not lost its thickness.

In addition, since fiberglass insulation does not absorb water, the insulation fibers will not be structurally altered or permanently affected in any other way. Because fiberglass insulation is manufactured from glass, it will not promote mold or mildew. Our fiberglass batt product is also tested to ASTM C1338 test method for determining fungi resistance of insulation materials and facings and passes this test.

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