There are 4 common types of insulation available for attics: fiberglass batts, cellulose, loose-fill fiberglass, and spray foam. Spray foam offers the best attic insulation performance available.
This types of insulation fill all of the holes in a space and make a flawless air barrier. Now, you have zero heat transfer through convection.
The only thing that you should know is that spray foam insulation is expensive stuff, and it shouldn’t be installed by a DIYer. It is better to an expert with a spray foam gun done this job for you.
A poorly insulated attic means an energy-inefficient home. In the cold season, warm air escapes from your living quarters into the attic and out of the house. In the warm season, warm air builds up in the attic and invades down below.
Insulation is the best way to keep it where you want it. And Insulation doesn’t last forever, nor is it impervious to weather, moisture, or mold.
If your home isn’t maintaining the steady and stable temperatures you’d prefer – or if your energy bill is higher than it ought to be — there’s a good chance your attic insulation isn’t up to snuff. So it seems you need to do something about the problem.
It might be the first question that bops your head “Can I Add New Insulation Over Old Insulation?”
Yes, You can absolutely do this. But you should consider that your old insulation should not be damaged by fire, water, or animals like rats. If so, unfortunately, you need to remove the old one.
Now by considering your budget and your other concerns like; energy efficiency, any health concerns you might have, and being eco-friendliness of the material, you can choose that you want to install new insulation over existing insulation or not.