Insulation, Radiant and Vapor Barriers - Blowing cellulose over blown fiberglass

Doityourself.com community forum was created to provide answers to all questions related to home improvement and home repair. Doityourself community can help you find information about how-to topics on small fixes to large remodeling projects. With comprehensive how-to content and expertly moderated community forums DoItYourself.com makes it easy to tackle even the most complex home improvement projects.



PDA
swandog1
12-18-06, 09:59 AM
In my attic the builder used blown fiberglass for insulation...at least I think it is blown fiberglass it is white and "fluffy"..and the house is 2 years old..anyways I am going to be blowing cellulose over my garage and I was thinking about adding some over the blown fiberglass in the attic...is this ok to do?

Thanks
Doug

Concretemasonry
12-18-06, 03:48 PM
The two types of insulation are compatible, so there should be no problem.

When you add insulation, make sure you do not close off the ventilation from the soffits to the roof vents.

Dick
XSleeper
12-18-06, 09:29 PM
Blown fiberglass is most effective when it remains "fluffy" as you put it. It's r-value decreases if it compressed. You can add more cellulose, but keep in mind that if you add 6" of cellulose, and it crushes the fiberglass by 3", you will still be increasing your insulation, but not as much. I wouldn't think that a light blanket of cellulose would crush the fiberglass at all.