Spray foam on roof of kneewall space? - Contractor Talk - Professional Construction and Remodeling Forum

Wideawake · 07-30-2007, 01:52 PM

I have a homeowner who wants to spray foam insulate on the underside of the roof of her knee wall area. Its a 1924 house with everything from wood chips to blown in cellulose, all of it not doing very much. I checked the internet and it seems possible but I'm wondering if anyone has ever done>? Any hiccups?

theroofinggod · 07-31-2007, 11:13 PM

I have a buddy in canada who just started doing it,you would seal to the sheetrock and leave ventilation space between the roof,the foam is very high r-value,and expensive ,approx.150 sq. ft. 1 " thick,about 150$ for material

Chris Johnson · 08-01-2007, 12:49 AM

Demilac has been approved to spray directly to the underside of the roof deck, I have used this several times without hiccups.

Wideawake · 08-05-2007, 11:50 PM

Thanks for the replies. I'm getting some concerns from the architectural techs that spray foam will create too impenetrable a seal for vapour, and that I should look at rigid foam panels instead. The current wood chips in the rafters, held by 10 inch wood boards, would stay intact. Not sure if this is good advice or not. any thoughts out there?

red_cedar · 08-06-2007, 06:14 AM

I dont mean to high jack the thread but this is of interest to me.

We are roofing contractors and will be involved in a project where the homeowners are going to have spray foam put right under the roof deck with no vented air space between roof deck and foam. I am concerned about venting. There are some gable vents on the house and I suggested more for a full cross ventilation of the roof attic cavity.

Sorry for the interuption, I hope this is adding a little to this thread.