Another foam insulation question, closed cell vs icynene?

[Dexter]

I'm thinking seriously about having spray foam in the roof of my new house (vaulted w/ no attic). Metal roof.
It's expensive but seems should pay itself off in time with the cold/hot temp extremes here.
Walls will be fiberglass as even the foam guys admit it really makes most sense in the roof.
Does anyone know the difference between Icynene and closed cell spray foams? I gather closed cell is water proof(wicks water from leaks down to soffit) while the alternate will allow leaks to drip into the drywall- allowing you to source a leak. Both good/bad. Not sure which contractor to believe, and both are the same price.
Any ideas would be appreciated! Thanks

[Old Vet]

You are right about the water. Most roofing companies use the close cell for the same reason that you have posted. I would use the closed cell. The good thing is that if you get some damage it will not leak unless it goes all the way through.

[Dexter]

Good point.
But I wonder if the compromise for no water leaking into home- is rotted plywood up there that won't be noticed till it caves in?
The roofer suggested closed cell- call me paranoid but closed cell would mean he won't need to come out for warranty issues as I wouldn't know my roof was even leaking.

[SolarGary]

Hi,
The closed cell has a much higher R value per inch -- its about 6.5 per inch vs about 3.8 per inch for the open cell. The closed cell stops water vapor -- you can spray it directly against the roof sheathing with no ventilation space because the foam keeps the water vapor from getting to the cold roof surface and condensing. The closed cell actually has some strength and stiffness, and will stiffen up the roof structure.
Unfortunately, the closed cell also costs quite a bit more.

You said you would use FG in the walls. I'd consider using cellulose.
Have a look at the ORNL report listed in this section:
http://www.builditsolar.com/Projects...htm#Insulating
Its titled: Convection Losses in Loose Fill Fiberglass Insulation

Or, go to the Finehomebuilding "Breaktime" forum, which has lots of insulation experts, and ask them what they think of FG -- or just search the old posts.

Gary

[PlowGirl]

I had the closed cell foam sprayed directly onto the metal of my quanset building. It is fairly stiff and a great insulator, plus sound dampening. It was a little pricey, but well worth the cost.
I don't know how much of a coincidence it is but, I've not had a single URI or sinus infection since the foam was installed over 7 years ago. I used to get them often during the winter.

[Mrrsteelers]

Originally Posted by PlowGirl

I had the closed cell foam sprayed directly onto the metal of my quanset building. It is fairly stiff and a great insulator, plus sound dampening. It was a little pricey, but well worth the cost.
I don't know how much of a coincidence it is but, I've not had a single URI or sinus infection since the foam was installed over 7 years ago. I used to get them often during the winter.

Probably not a coincidence, spray foam is insect and mold resistant. It fills every nook and cranny, and then continues to expand for a couple hours. It's great stuff, but we rarely get to spray it because of cost.

[PlowGirl]

Originally Posted by Mrrsteelers

Probably not a coincidence, spray foam is insect and mold resistant. It fills every nook and cranny, and then continues to expand for a couple hours. It's great stuff, but we rarely get to spray it because of cost.

Then it was definitely worth the extra expense.

[wally]

Not sure this will help but some friends are buiding a new home here in kansas and the company doing a 1800 sf ft home wants to spray the walls ( not sure of the kind) and put fiberglass in the attic. total cost around 9000.00 due to the 6 inch walls. The roof is a mix of metal and shigles..dont ask me why

[WisJim]

Usually they foam the walls as a first choice because it does such a good job of sealing against air and moisture leakage, which is almost impossible to do equally well with fiberglass batts.