The previous owners of our 80-year-old house had put insulation in the attic. Leaky shingles on the roof and a bathroom vent that shot up directly into the attic has caused the insulation to flatten considerably. We are going to replace the shingles and install a bathroom exhaust. Once that is done, is it necessary to replace the flattened insulation, or is it possible to somehow salvage it?
Whether or not you can salvage the flattened insulation depends on what kind of insulation it is. If it is fiberglass or rock wool, it can be fluffed back to its original appearance. You can use any garden tool or a large-shaped fork to do the trick. If the insulation is cellulose, you will have to replace it. Cellulose insulation becomes hard when wet, turning into something similar to papier-mâché. The flattened insulation may have blocked some of the vents, so be sure that they are clear of any blockage. While you are at it, check for rotten wood. Lastly, it is very important that you redirect the bathroom exhaust out of the attic and not out the soffits, where the hot moist air can simply rise back into the attic.