Icynene, Roof Venting and Shingle Damage
I am largely reconstructing my house (75% new), with new second floor rooms under eaves. I would like to have incynene insulation installed, applied directly to the underside of the roofing deck, from the soffits all the way to the ridge. I could avoid having to install soffit vents, ventilation channels or ridge vents (less $$). My thoughts are that this would give me a tighter house, and lots of conditioned attic space.
I’ve heard concerns about composite shingle life, but some articles I’ve found indicate that this approach does not significantly reduce the lifespan of a good quality shingle, or of the decking. I live in a moderate Northeastern climate.
Agree? Disagree? Concerns?
Replies
How deep are your rafters? In the northeast the problem is ice dams so we try to keep our heat in the living space and the attic at the same temperature as outside. That's what the venting is about. R-38 is the minimum insulation value for ceilings. Can you get that or more with isocyene? Any less and you will have problems. The sun and UV rays break down shingles. If the attic is only for storage I would not heat it. If you are on the Jersey coast with little or no snow the insulation will be more important for keeping the heat out in the summer. In either case the higher the r-value the better.
Thanks for the helpful feedback. Almost all of the attic is living space. The r-value for Icynene is 3.6 (about the same as fiberglass). That would mean I would need 10-1/2" to get r-38 or 8-3/8" to get r-30. I will have to find out what local code will require. I am still pursuing this. I am convinced that it is going to give us the most efficient house.
Thanks again.
Two points.
The fiberglass R rating is theoretical. Installed fiberglass is usually nowhere near what the advertised value is. And, as temps fall R value of fiberglass decreases.
The foam will give you the actual claimed value, AND it will be in all the spots the fiberglass installers missed.
How's the headroom? You could add a couple of inches of foam sheet on the inside to gain more Rs.
Joe H
We recently had an Ohio Icynene@ dealer tell us it was not necessary to spray more than 6 inches (they srayed an average of 6 so it went from 3-8 inches) in a 2 x 10 cathedral rafter because anything over 5.5 inches was inefffective and wasted. The brochure states 3.6 per inch but they said the factory said "it works as good as". I called another Icynene@ dealer and they confirmed this practice. The building inspector turned it down based on the required R-38, at 3.6 per inch which gave us an average of R-22. The dealer and Icynene@ manufacturer could not back it up so they came back (four months later) and re-sprayed to get R-34 which the inpector accepted. Although it is a good product, make sure you get what you need.
You will have a better job of insulating and tightening the house.
You will as you say have a conditioned attic that is cleaner and drier than if it is open to the great outdoors. No drafts & less creaking and groaning when the wind blows.
Shingle life would not be a consideration in my choice, I think the shingle companies see it as an excuse to void their warranty. A vented roof in Florida gets much hotter than yours.
Go for it, it's worth the bucks if you have them to spend.
Joe H
Thanks Joe! Exactly my thoughts. I am convinced that this will give us the lowest energy costs.
We will see what the estimates come in at. Lets hope I can find competitive bids in Southern Connecticut.
Competitive bids in Southern Connecticut? You are an optimist! <G>Andy Engel, The Former Accidental Moderator