Thread: Icynene underneath a slate roof

Did a 100+ year old victorian with a slate shingle roof. First time I have seen Icynene underneath a slate roof. I didn't get a good feeling about it. Old slate roofs tend to leak here and there. Where's the water that gets past the slate shingles going to go? There must be other reasons why having this foam insulation under a slate shingled roof is not good. Could use some other opinions.

The knob & tube wire in the photo was dead but what if it wasn't?

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Originally Posted by Dennis R

Where's the water that gets past the slate shingles going to go?

That's always been my concern with Icynene since I first saw it.

On an existing house like that, there is little or no UV burning of the surface from sunlight, but on new construction the surface receive quite a bit of UV burning and gets much harder than even the surface skin in your photo.

I've taken big left over gobs of the stuff, pulled out some of the inside stuff, and filled it with water - which stayed there and never seeped through (like it is supposed to do).

The only way you would know you had a roof leak is when someone was on the roof and the truss (rafter in your case) failed because it was rotted out.

The knob & tube wire in the photo was dead but what if it wasn't?

Dead? Or just switched 'off'? Could you see the cut off and abandoned end of the "dead" section?

Originally Posted by Dennis R

The knob & tube wire in the photo was dead but what if it wasn't?

Knob and tube hot and neutral are separated. Maybe that's the neutral?

This might help if I did the attachment right.

Unvented Attic System - 7pt.jpg

unvented attics.pdf

unvented%20attic%20and%20cathedral%20ceiling%20construction.pdf

Vol10_01_CathedralCeilingRetrofit.pdf

David,

That's the *theory* behind it.

In practice, you must take into consideration real life application problems and environmental effects. The problem is that in real life applications the covering skins over must harder, and is burned even harder by UV when exposed to sunlight, that it becomes much more resistant to moisture and water penetrating through the skin.

The sample and tests I did showed that the foam would hold *a lot* of water for *a long time*, and (as the foam is sprayed directly onto the wood) that means holding lots of water for a long time directly in contact with wood. Which is not necessarily a *good thing*.

Mostly, the concern is from, as Dennis said "Old slate roofs tend to leak here and there. Where's the water that gets past the slate shingles going to go?", "leaks", not necessarily the moisture traveling with and through the air (which is what that attachment is about).