If you go into your attic and find that your insulation feels moist, it's important not to ignore this issue. Not only will mold begin to develop in the wet insulation, but the ability of your insulation to block heat transfer will be impeded, so your energy bills may shoot up and your home may grow cooler (or warmer in the summer.) There are two common causes of moist attic insulation: roof leaks and poor attic ventilation. Here's how to proceed in each case.
If the moisture seems concentrated in certain areas, then a roof leak is most likely to blame for your wet insulation. See if you can trace drips or water lines along the attic ceiling back to a specific location. Also, take a look at the outside of the roof. While missing shingles are an obvious source of a leak, also look for nails with exposed heads and loose flashing (the metal around the base of chimneys and other items that project from your roof.)
Once you identify the source of the leak, hire a roofing contractor to make a repair. Or do it yourself if you're handy and confident climbing on the roof. Only once the leak is repaired should you replace the insulation. Otherwise, the new insulation will just get wet, too, if the roof leaks again before you get the chance to fix it. You can replace fiberglass batt insulation quite easily by rolling up and bagging the old insulation, and then unrolling new rolls of it across the attic floor. Remember to put the second layer perpendicularly across the first one.
Lack of Ventilation
If you cannot find a place where the roof is leaking, then you probably have an issue with inadequate ventilation. When hot air accumulates in the attic and then the temperature drops, water condenses out of the air and moistens your insulation.
Adding ventilation to your attic is a job for the pros. Your roofing company will either have to add some new soffit vents along the edge of the roof or install a ridge vent along the roof's ridge. In extreme cases, a large attic fan may be needed to air the space out. Once your roof is venting properly, you can replace the insulation without worrying that the new insulation will get wet.
Don't ignore moist insulation! The longer you let it sit, the greater the chances that it will mold, leading to respiratory difficulties and allergic reactions. For more information, talk to insulation contractors by Green Penguin Insulation.