Impacts and repair of disturbed blow-in fiberglass attic insulation
I topped off the blown-in fiberglass attic insulation last fall after performing air sealing. I received a thermal camera for Christmas and have identified some areas that should be inspected. It seems clear that the insulation will never be the same after it has been disturbed (even small disturbances created when insulating my attic hatch have caused noteworthy settling and clumping). How much will the new insulation be damaged by investigating these newly identified anomalies and what is the best way to repair it? Will leveling it and then adding new insulation to maintain the original depth restore the full r-value, or close too it?
I live in climate zone 6.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
You can run old fiberglass insulation through a blower and reinstall it again with no impact on performance. You can manually reshuffle it too, but you'll probably have a small reducation in performance since it won't settle as evenly this way. There is a product called "shake and rake" that is loose fill fiberglass specifically made to be installed without a blowing machine. This stuff is GREAT for small patch jobs, or insulating small areas with loose fill insulation. While the manufacturer says you could insulate your entire attic with this stuff, I think that for larger areas it would be much more efficient in terms of labor to use a regular blowing machine and not the shake and rake product.
If you spread stuff back out as evenly as you can, making sure to break all the clumps up into small bits like when it was newly installed, you'll get it back to near original performance. Adding some extra over the top would be a good idea if in any doubt.
Note that blown cellulose is MUCH less tolerant of rearanging like this.
Bill
Good info. Thanks for your response.
I am a little surprised to hear that cellulose is less tolerant to movement. I'm curious to know why this is the case? Is it related to clumping?