Spray foam in attic
 

I have gotten some conflicting advice regarding spray foam in my attic. I currently have blown in insulation covering 90% of the attic and the other 10% is batts over a vaulted ceiling. I am considering adding spray foam in the spring and was thinking of spray foaming the underside of the roof vice the actual attic floor. I recently read an article on this

http://www.sprayfoam.com/spps/ahpg.cfm?spgid=66

and have been advised to remove the current blown-in/batts and stick to spray foaming the floor. Any additional advice and comments (especially from those that have spray foamed the underside of the roof) are welcome.

I have read and read on spray foam. some good, some bad. I know that the chemical mix is the most important thing. that being said,


if it were me, I would want the fiberglass etc removed, the area cleaned and the upper side of the ceiling foamed, not the roof plywood etc.

I dont like the idea of a conditioned attic with no ventilation. I dont like the added expense and more foam and more weight on my roof (I have tile already, which is heavy) also roof repairs would be harder.

with it on the upper side of the ceiling, there would be less foam used, less weight used and gravity would not be trying to pull it loose. also, this way it seals the ceiling from air leaks.

just my thoughts based on my reading and opinions...

Spraying the ceiling would add more weight to the ceiling. Any romex ran across the rafters would then be insulated, and have to be derated.

Spraying the roof and gable ends works good. A small supply and return is all that is need to the sealed attic.

What is the ROI

Return on Investment time?

If it takes 10-20 yrs to pay for itself in NRG savings then whats the point? Where I live and it gets to -40F or C we use R40 blown in the attic. If all that extra insulation was important then we would be going higher than that. Point being that unless you are in Alaska why would you need more than R40. Sounds like overkill 2 Me.

Better bang for your buck would be improved 3 pane low e argon windows IMO. Most basic windows are less than R4 and look how many you have and the total exposed area.

Beside the insulation value. the sealing of the attic greatly reduces the heat loss and gain.

Up where you live, you guys already build your houses much tighter then we do down here.

Probably true. We caulk and seal all the joints in our vapor barrior etc and yes we build very tight. I would hate to try that spray foam idea and then 10 yrs later they find it is causing structural damage to houses or some other problem like with UFI formadehyde insulation. Point being that it takes 10 yrs B4 the REAL problems show up and I would not want to be the guinea pig to find out and then have to remove it.

We've already done the low E windows and are working on the doors. I probably wouldn't do spray foam except a mutual friend owes me a favor, and would do the work for a good price. Of course, I could also just add additional blown-in insulation; just thought I might try the spray foam route.