icynene foam insulation

[sadiebelle]

We live in Northern New York. Our home has cathedral ceilings with no air space to the metal roofing, in the winter we get severe condensation and leaking. We were told that removing the metal roof and having the spray foam put in then a 2" air space, plywood and metal roof put back on would be the answer. Does the icynene work on roofs or only attics? It can get as cold as -50 here and when the heat goes thru the ceiling we need to have it stopped before it gets to the cold of the metal. Please advise

[Nexus7]

If you can stand to have the ceiling dropped 4" or so, you could put up drywall separated with 2x4 from the present ceiling, and fill the air space with insulation.

Where do you get condensation? I'd think it'd be inside the house, not between the ceiling and the metal roof. In that case, the warm air has to be stopped before it gets to the present ceiling.

[Joseph Meehan]

Well, it will work, but it will only be 2 inches. That may or may not be sufficient to fix the problem. In Northern NY I would think that only 2 inches even icynene would be minimal at best. It is possible to add more above the current roof or below. I would want a second opinion from someone in the business in the area. It just seems like you may regret not doing more.

[ransley]

I dont know what R value icynene is but there is R 7.5 foam from Honywell, R 75 would be great if you could do it, code for my area zone 5 is r35 but codes are minimums and outdated, Id say R 40 would be a minimum , I have R 100. Doing all that work and not putting in enough R would be a waste.

[Cliff Hartle]

Its 2 inches of air space not 2 inches of foam. Depending on the size of the rafters you would get 6" to 10" of foam.

[Chris Friesen]

Icynene is only R3.5/inch, but doesn't offgas and doesn't shrink as it ages.

Just curious...did you calculate the payoff period for R100 over R50?

Chris

[scott21230]

if it were mine I would have a regular (not vaulted) ceiling put in and insulate the crap out of it. My second best choice is the drop ceiling with lots of insulatino. 2" of insulation is everly inadequate in NY. I'd want at least 12" of insulation, but since you most likely have the space I'd want something much greater than that even.

[Pat]

Why wouldn't you blow in cellulose instead?

[Chris Friesen]

One advantage to many of the spray foams is that they also act as a vapour barrier. This is useful for retrofit work as it can often be difficult to install a proper vapour barrier after the fact.

Chris

[Pat]

Yes, but he's in upstate NY and blow in is much more common.