Eben writes from Wasilla, Alaska: "We built our home last year and just last week we sprung a leak on the window next to the fireplace (the leak was about a pint or less in a bucket). The builder replaced the metal fireplace cover on top of the chimney. Assumption here is that this was the cause of the leak. I know the insulation is wet because I opened an electric outlet box on the wall and placed a Q-tip in the crack and it got wet. The builder fixed the leak and says that the fiberglass insulation will dry out. Should I open the wall space and check it for wet insulation and replace? There has been no leak since replacement of the metal fireplace pan above."
Answer: When fiber glass building insulation becomes wet it will temporarily lose some of its thermal resistance (R-value). The amount of loss depends on the degree of water saturation. In this case, the spaces between the fibers that were previously occupied by air would be occupied by water. Since water is a much better conductor of heat than air, its presence would cause the insulation to "short circuit."
However, fiber glass insulation does not absorb water and the insulation fibers will not be structurally altered nor permanently affected in any other way. So, provided the insulation becomes dry again and regains its original thickness, it will regain its original performance level.
A physical and visual inspection should be done to ensure the insulation is dry. If the insulation is wet, Owens Corning recommends that it be removed from the cavity space to ensure that the insulation and facing (if applicable) are completely dried. Drying time may vary depending on the wetness of the insulation, ambient air temperature and relative humidity.
In the case of dirty or contaminated water entering the product, there is only one answer - replace it! Whenever any foreign substance (dirt, mold spores or bacteria) comes in contact with the insulation, we advise you to remove and replace it. The moisture and foreign substance can support mold and mildew growth and even give off a musty odor.
The Kraft facing should not deteriorate when subjected to water. There is a possibility of discoloration but the water should actually be repelled by the facing due to the process in which it is manufactured.
