I'm in the process of replacing my windows and siding, and I've been thinking about upgrading my wall insulation while I'm at it. The house has its original fiberglass insulation from the 1960s. One contractor says it's a good idea to remove the old sheathing and replace the fiberglass with new insulation, but another contractor thinks that would be impractical and suggests just adding rigid foam board over the existing sheathing instead. He claims that adding foam is cheaper and more efficient since it offers better coverage. I'd love to hear what others think about this approach and if it's worth the effort to replace the wall insulation.
3 Answers
Foam board will give you continuous insulation and can serve as an air barrier, which is great for noise reduction too. If you choose to go for foam, strip the siding first and deal with the insulation in the stud bays before you put in your doors and windows. Just remember to get jamb extensions to match the wall thickness afterward.
Are you sure the original insulation is in bad shape? Adding foam can stop thermal bridging through the wall studs, which simply changing the interior insulation won’t fix. Plus, it helps with energy efficiency.
Great point! I never considered how thermal bridging affects efficiency. Not sure about the condition of my insulation though.
So if I go this route, do I just hang vinyl siding on the foam? Or do I need to secure it through to the sheathing?
If you’re already insulated on the inside, adding rigid foam on the outside is hard to beat. It really helps prevent thermal bridging. Just make sure to tape and seal everything properly for maximum efficiency!
As a contractor, I completely agree with this. Using rigid foam on the exterior is a smart move.
I hear you, but my contractor suggested leaving the old insulation as is and just putting the foam over the existing sheathing instead of swapping the fiberglass.