Are Owens Corning Premium Cool Architectural Shingles worth the cost?
user-7005676
| Posted in General Questions on
We are in zone 6 and planning not to vent our roof to wall new addition. We plan on using I-Joists with 4 inches of closed cell cell spray foam (R26) against the underside of the roof sheathing and fill the rest of the rafter cavity with an air-permeable insulation, additional fiberglass R25 underneath.
Wondering if it is worth the cost, (more than double) for this “cool” architectural shingles?
Thanks for any advice you can provide
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Replies
User-7xx, in cool climate zones, "cool" roof surfaces typically don't make much of a difference one way or the other over the course of a year. There are situations where heat-absorbing roofing can be a good thing, both for the free winter heat and to help with moisture control in the roof assembly.
You didn't ask, but I have to add--if you are set on using spray foam, have you considered using one of the new HFO-blown products, such as Lapolla Foamlok 2000 4g or Demilec HFO High-lift? Their blowing agents are much more benign than those in conventional closed cell foam, which are potent, persistent global warming agents (aka carbon polluters). Plus the HFO-foams have higher R-values.
Thanks for the quick response. I was thinking of going with a local contractor who uses BioBased 1701s, a water-blown closed-cell foam. which doesn't use either CFCs or HCFCs as blowing agents. Has an R value of 18 at 3.5 inches.
User-7xx, that's an interesting looking product, really somewhere between what is usually considered open cell and closed cell. It's semi-vapor-permeable at 1" (2 perms) and semi-vapor-impermeable at 2.5" (.73 perms), but extrapolating those numbers it should be fairly vapor-closed at 3.5".