Thread: Spray Foam

I'm going with foam for insulation on my new home. The sales guy and friends are trying to talk me into spraying the roof-line as well. What are your thoughts on pros/cons cost vs benefit ?

Thanks.

Roof is the best place to use the foam. no cons with spray foam other than upfront cost is a little more than fiberglass batt insulation. I think I posted some videos in my other thread on here showing it being applied.

Here was a pic in my other thread showing a roof where half (newly renovated part) has spray foam, and other half doesn't. You can see how the half with foam still has frost on the roof as very little heat from inside the home escapes through the roof to melt it.


*note how you can even see the individual roof rafters as more heat transfers through them than the foam insulation

Here was the post Some Pics of our Projects
along with the video

Spray foam works great, but I'd be careful about spraying it directly on the underside of the roof sheathing. You might end up with a "hot roof" which will shorten the life of your shingles.

Maybe J08M3 could clarify this for me, but I've seen a couple roofs on additions that were foamed and the shingles on the foamed portions of roof deteriorate much faster than the non-foam portions next to them. It looked to be like the shingles on the foamed portions were staying hotter in the summer. Maybe the wrong type of foam was used?

Originally Posted by RT3

Spray foam works great, but I'd be careful about spraying it directly on the underside of the roof sheathing. You might end up with a "hot roof" which will shorten the life of your shingles.

Maybe J08M3 could clarify this for me, but I've seen a couple roofs on additions that were foamed and the shingles on the foamed portions of roof deteriorate much faster than the non-foam portions next to them. It looked to be like the shingles on the foamed portions were staying hotter in the summer. Maybe the wrong type of foam was used?

What type of shingles? asphalt, cedar?

I'm using "spanish tile"

Check into Soybean foam. Its environmentally safe a better r- rating than regular foam.

Originally Posted by rstang42

Check into Soybean foam. Its environmentally safe a better r- rating than regular foam.

I've used it and it's not exactly what it's hyped up to be. The R value is no different than "regular" foam, and it's still a petroleum product, only part gets replaced with soybean. The flip side is now you are cutting into food supply which many critics argue is far from green.

It's a comparable product, use either one you like. See who gives you better pricing.

Originally Posted by J08M3

What type of shingles? asphalt, cedar?

Asphalt shingles.

Originally Posted by RT3

Asphalt shingles.

I never heard of this issue with asphalt shingles. When we build cedar shingle roofs we use a double layer of lathe to let the shingles breathe and prolong the life of them. Due to local building codes (but also for energy efficiency) solid sheathing is required for roofs here. So we always used double lathe. The shingles breathe and the spray foam is directly applied to the plywood sheathing beneath.

There's a lot more info here:
Foam Insulation for Vented or Unvented Attic Spaces - Spray Foam Information Directory - SprayFoam.com