insulation

[Raider Bill]

Scott,

What do they charge per sqft for the spary in?

[scsmith42]

Bill, I don't know but I can ask.  I was fortunate in that the owner of a spray-foam insulation company is building a house near my farm, and we did a trade out (I did some grading work at his homesite and he insulated my farmhouse project).  To do the entire perimeter walls of the house 24 x 36 x 10', plus the upstairs end walls (14' tall) and the rafters(12/12 pitch - about 15' of exposed underside), he originally estimated around $3,500 - $4,000.00

Running the numbers, the house ( 24 x 36 footprint 2 story) has around 8,600 square feet of 3" insulation (lower walls), 330 square feet of 5" insulation (upstairs end walls), 1000 square feet of 6" insulation (roof), and 864 square feet of 3" insulation (upstairs floor for noise deadening).  The insulation guy recommended - whenever possible - leaving an air gap between the insulation and the drywall, versus totally filling in the space, as the airgap provides additional insulating properties by reducing thermal transfer from the foam to the drywall.  I couldn't do this on my 2 x 4 walls, but could on the 2 x 6 and roof joists.

In general, I'm told that 6" of open cell spray foam costs about three to four times the amount of 6" of fiberglass.

My insulation guy tells me that the "R" value measurement typically used for insulation is not totally applicable to spray foam, and that the actual performance is about twice the "R" rating.  I think that this is partially based upon the fact that properly applied spray foam will insulate in areas where fiberglass cant (such as behind an outlet box installed in a 2 x 4 stud), and also that it provides a complete vapor and draft barrier when properly installed.

One thing that I noticed in my farmhouse project, was that the open cell foam provides significantly more noise insulation than fiberglass.

Scott

[Raider Bill]

In my case with a ICF house I can't see skimping on my ceiling insulation. If I did the ICF's would be a waste. Through this building process I've saved some $$$ by not going timber frame and by doing all the work myself so I can and will apply that to a super insulation overhead.

[Qweaver]

Scott, the only problem that I've found with skip sheathing is the occasional rain of condensation that I will get on a sunny morning after an overnight frost.  Full sheathing with 30 lb felt over that stops that problem.  For some reason I don't have the condensation problem in my saw shed but I get a real "rain" in my motorhome shed.
Quinton

[scsmith42]

Quinton, thanks for the tip.  I'm hoping that by spraying foam 100% on the underside of the tin/skip sheathing, I will eliminate the condensing surface and prevent the "rain".

SS