Wet insulation


Old 03-21-03, 09:14 PM
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Wet insulation

My contractor left 15 rolls of R-30 fiberglass insulation bagged in plastic outside. We got a heavy rain storm lasting many hours. Most of those bags now contain wet insulation. Some have told me that you can not use insulation that's been wet no matter how well you dry it out because it will grow mold once installed inside the walls. Other's have told me that once it dried out, it's fine to use and hasn't lost its insulating ability. Anyone got a suggestion for me?
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Old 03-22-03, 07:10 AM
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It depends.

Glass will not rust or rot because it has a very low absorbancy and fast expulsion rates towards moisture. Once the fiberglass insulation is dried, in most cases you can install it without any adverse effects. Fiberglass should never be installed when it is wet. Because it will transfer the moisture to the structure almost immediately. Depending on the amount of moisture and other applications used in conjunction to install the fiberglass, the fiberglass may trap the moisture inside the structure and create a situation where mold and mildew may prosper. Example is an air barrier like Tyvec.

The 2 other concerns with wet fiberglass is compression and vapor barrier deterioration. What gives fiberglass its thermal effect is the trapped air inside the insulation. Compressing the insulation reduces the thermal effect dramatically. In most cases when the fiberglass dries out it will go back to its original form. It is when there is dirt or dust on the insulation and the moisture forces the debris inside the insulation is when the fiberglass will not go back to its original form.

Most vapor barriers are moisture resistant. But are not designed to be immersed in moisture. This will usually degrade the tabs used to staple the insulation and the adherence of the vapor barrier to the insulation itself.

So if fiberglass insulation is to get wet like in your situation, the inspection of the insulation prior to installation is warranted. If any of the aforementioned conditions exist, then I would not recommend the insallation of the insulation.
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