Attic Insulation, Can they be mixed?

Can a different type of insulation be placed over an existing fiberglass insulation, already in place? I have only 12 inches of fiberglass insulation in my attic. A contractor said that I needed to place additional insulation to bring that up to 20 inches. Another contractor said that I could use cellulose over the fiberglass.

Question is? Is there any reason you can’t use a different type of insulation on top of the existing, such as cellulose? Or would I be best to keep consistent, and use the fiberglass insulation? Is weight a factor? Do I REALLY NEED 20 inches of insulation. I live in hot north central Texas.

Fiberglass seems to cost more, so cost is a factor as well. But, I also am concerned about cellulose becoming a fire hazzard. What are my best alternatives here?

Gerri Williams

Dbl post

Adding different insulation on top is okay.

Cellulose, typically, has a flame retardant added. It closes off gaps better that batts, IMO.

Here are some links to help you decide but adding anothe 8 inches of cellulose on top of 12" of batts may be a little much.

Recommended levels of insulation:

Adding insulation to an existing home:

Estimating the payback of adding insulation:

I see different insulations all the time. No problem.

I did a commercial building some time back that had 3 different types of insulation. They built out the building in 4 different stages. The first 3 attic areas each had a different type of insulation (probably whatever was cheapest at the time of buildout). The 4th attic area had a mixture of the leftovers of the first 3.