NonVented Cathedral Roof Foam Insulation
Hello all,
I am new to this forum but from browsing around it looks like there are a lot of very knowledgeable people here with a lot of very helpful information. I am hoping you can shed some light on a project I’m working on now.
I have an old new england home, about 100 years old, which I am renovating from top to bottom. The roof is a hip with a steep pitch that provides for a very large attic room. The roof was re-done very recently as was all of the siding, sofits, etc. Currently the rafter bays are un-vented. My plan is to finish the attic space with a master bedroom/bath set up. What I would like to do is have spray foam insulation applied in the rafter bays and then cover with drywall to create an un-vented cathedral ceiling.
My question is: With all of the different types of foam insulation available, which would work best for this set up and region? The roof is brand new standard asphalt shingles – with the rafter bay being un-vented and insulated, will this have a negative affect on the life span of the shingles? Any tips/tricks I should know about an application like this? Finally, can anyone recommend a good installer in the Springfield Massachusetts area?
Any advice/info you guys can give me would be greatly appreciated.
Thank you in advance,
Ed
Longmeadow, MA
Replies
Oh boy, did you ask a loaded question. In a few sentences I can say there are at least 2 types of spray foam, open-cell and closed-cell. There are questions about whether your shingle manufacturer will void your warranty if you create a hot roof. One question, you say the rafters are not vented but is the attic vented otherwise (dutch-hip vents?).
In any case, this has been covered in tremendous detail in the past. If you do a search on 'foam insulation', I'm sure you'll find a lot of reading material.
http://www.corbond.com/main.htm
Beer was created so carpenters wouldn't rule the world.
Only the shigle makers will make any sort of claim about unvented roofs changing the shingle lifespan. They will not produce any data or evidence to back such claims up (the warranties are all written as if it were true, though--but, many, many other things invalidate shigle warannties if they want to be pedantic about it.).
The only thing about insulating the roof, is tying that insulation into the walls in a uniform and "tight" matter (none of this is much good if there's a "gap" between roof and wall.
This is a good place to talk to prospective insulators to get a feel for the contractor. If your insulator has a blank look when you talk about the wall to roof conncection, you might want to talk to a different insulator (or not--said worthy might just be glassy-eyed, too).
Now, to my thinking, you ought to insualt over the ends of the rafters, too, otherwise, the heat travels through the rafter and into the drywall you have over that. Even an inch of rigid board over the rafter bottoms will help keep simmer heat out of your attic room.
Ed,
You came to the right place. I guess I did too....
I own a spray foam insulation company in East Longmeadow, SAFCO Foam .
We install both Corbond, which an earlier poster recommended, and also Icynene. Both highly regarded and leaders in the industry.
Please feel free to contact me or visit me at the home show at the Big E in West Springfield tomorrow (Sun 10-22) from 11a-5p. I'm just in the front door to the left. If that is not possible simply visit my web site http://www.safcofoam.com and you will find all my contact info.
There is another Icynene dealer there as well that you can speak to for a second opinion if you would like.
The effect on shingle life is negligable. Moisture in the roof is a far worst problem then a slightly higher temperature. The foam lets no air movement thru so eliminates condensation against the roof deck or in the foam for that matter. Let me know the shingle manufacturer and I can help determine if they fully warranty their product in a 'hot' roof application. Elk, Certainteed, and others do.
Look forward to meeting you!
Stuart
I used Corbond in my unvented vaulted ceiling in my formerly 3 season, now 4 season, porch (and in the walls and floor too). Great stuff.