Polyurethane Foam used in rafters

Started running into this used to fully encapsulate the attic making it part of the building envelope. I have only seen this in my area twice. Would like to know if anyone has long term experience with this and any issues. Does it keep the attic cool enough in the summer? Is there any decking decay issues with the open cell type foam? Just wanting to get more of a feel for this product and procedure. Thanks

An older thread on same topic I think.

Green Building adviser has a good forum on it. Sprayfoam has become very popular over the last couple of years. Hope this link helps. I usually go in there to read on green building.


How was the home exchanging air? Spray foam makes a home so tight that there should be a system to exchange air, whether it is as simple as bathroom fans on timers or an air exchange system for the whole house.

The OP is talking about the attic. It is not ventilated.

Spray foam reduces conduction through the roof, lowers convection in the attic, and blocks radiation. But it may raise the roof temperature which could damage your roof materials (where you work).

Hybrid applications that still ventilate the roof deck (on top or from baffles underneath) reduce the temps.

Open cell does not hold water.

Yes, it still gets hot. But have you inspected many attics in Tennessee in the summer?
Any reduction of temperature differential between the attic and interior of the house is significant. If you simply lower the average attic temperature by 10 degrees, that is ten times less heat transfer through the ceiling.


This article may help a little. :slight_smile: