We are homeowners building our on buildings.  We recently built a 6,000 sq. ft barn out of ICF’s (Insulated Concrete Forms).  When we designed this building we were influenced by someone who had built in this manner.

For roof insulation this person sprayed a semi-open celled soybean product (icynene-requires dealer installation) directly to the underside of the roof sheathing and trusses.  The attic is unvented.  The amount sprayed was only 5-7 inches which technically doesn’t meet code but when compared by performance it is supposed to outperform traditional insulation methods of R40 we were told.  (We have not been able to verify how this building has performed)  This building was located in northwestern, PA.

In theory this works because the spray foam air exchange between the outside air and the conditioned inside air therefore there is no point for condensation and moisture is not an issue.

We have sinced meet another builder who has used similar approaches but has also been required to add additional insulation to bring the R value up to the R40’s required by code.

This builder had some initial problems but is now doing a third house with some adjustments.

There is information about nonvented cathedral ceilings at www.buildingscience.com/resources/roofs/unvented_roofs_summary_article.pdf and other sources.

We are looking for anyone who has had any experience with products such as Icynene, Tiger Foam, Selection500 or other means of doing unvented cathedral ceilings.

Any help out there?

Sincerely,

Darbie