My new house has some old fiberglass insulation in the attic. It’s matted down with dust and has lost most of its fluff. I want to know if I need to pull it out before putting in new insulation or if it’s OK to just plunk new stuff right on top of it.
I don’t see how there would be a problem, but i’ve been know to be wrong on this type of tying.
In general, the more insulation you have, the better - it should be more effective overall if you just leave it in place.
Unless you’re planning to install boards on top, and the combined thickness means compressing the insulation considerably - that could render it less effective.
I’m with Mangetout. Leave it be and put the new stuff on top. I did this with my house. I would not recommend putting boards over it. If you need to have access I’d lay out a path with 2x6 that way you minimize compression.
Thanks, that’s what i figured. But i could foresee someone telling me the dust created a fire hazard or something like that, so i wanted to check.
If the dust is between two layers of non-flammable fiberglass insulation, I don’t think you are increasing a potential fire hazard as decreasing it. Of course, just make sure any electrical fixtures in the ceiling are well ventilated (think ceiling fans and ceiling lights) so as to prevent creating a fire hazard. You don’t need to pack insulation directly against the fixture; in fact, the code probably states that should not be done.
I’d check to make sure you have eave vents. They are inexpensive Styrofoam shields that keep the insulation from cutting off the air circulation. Without them, moisture builds up and you get mold & dry rot.
It should look just like this. Every few feet along the attic wall. Then outside, there should be a few soffit vents. It’s even more important when you pack in a lot of insulation.
http://www.sunsethomerepair.com/blog/wp-content/uploads/2009/02/soffit-vent.jpg
A couple of years ago a tree hit the house I am renting. there was not nearly as much damage as there could have been - the tree luckily hit the brick chimney at the corner, which stopped it pretty effectively. There was just a small 1 foot square hole in the ceiling in the den.
Well, that and the ancient fiberglass fromt he insulation, which disintegrated and spread throughout the house. The house in which my baby was crawling.
It was a complete nightmare. Not just the fiberglass itch as we just couldn’t clean enough to get it all up, but the neverending sinus infections from the dust mold and mildew it brought in with it.
Get the old stuff out of your house, and treat it like asbestos. . .
Make sure there’s no insulation in front of those vents, too. Put up the eave vents, then insulate around them - underleath, but not over the soffit vent. That just ruins the whole point and also leaves you with wet moldy insulation.
“Treating it like asbestos” means, to the intelligent trained asbestos professional, that you don’t fuck with it. Seal it off and leave it be – and that good advice for old insulation, too.