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Cost to install exterior foam or Roxul?

I am curious about what the installation labour costs are for exterior insulation boards - foam or Roxul. For comparison, lets just say one layer that does not include taping or caulking. Does anyone have a cost per square foot of wall or floor area that they charge or have paid?

My only experience is with the rigid mineral wool boards and that cost $4,600 for materials for two dwellings which I figure is about $1.09 Canadian per square foot of wall area (or 2,900 square feet of building space.) The installation cost was $5,000 or a little over $1/sq. ft. of wall area. The siding, strapping, housewrap, flashing came in around $20,000 which was $2,000 over our quote. I would attribute most of that extra to the strapping installation over Roxul and some adjustments to the new product, but also some was due to extra taping and air sealing we insisted on.


Asked by Patrick Walshe
Posted Feb 20, 2013 3:06 AM ET
Edited Feb 20, 2013 5:42 AM ET


3 Answers

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A lot depends on local labor cost, the scrap fraction from cutting around windows/doors, as well as the size of the project. In my area on very uniform surfaces (rectangular roof pitches without valleys) EPS and iso can run as low as 12 cents per R-foot (eg: R10 runs $1.20 per square foot, R20 about $2.40, installed.) But on walls with window & door openings there is a larger scrap rate, more labor in cutting & fitting, which can come in close to double that. At relatively low R (say, R15 or less, single layered) the labor rate is pretty constant independent of R-value, but goes up with multiple layering & air sealing.

Both the complexity and R-value makes the installed $/R-ft highly variable, making it sometimes cheaper to go with closed cell spray polyurethane foam (effectively zero scrap rate, self-sealing & flashing, running 17-20 cents/R-ft installed no matter what shape or R-value.) But there are other issues with ccSPF that have to be factored into the design and design goals.

I have yet to use rigid high density stone wool but my understanding is that the material cost per unit-R is higher than EPS or iso, either of which tends to run around 9-10 cents/R-foot f.o.b. the distributor's yard, give or take. XPS is usually a bit more.

What thickness or R-value were you getting for $1.09/ft? Any idea what the scrap-fraction was?

Answered by Dana Dorsett
Posted Feb 20, 2013 12:20 PM ET


1.09 / sqft was 2" roxul R 8.4 - not sure of scrap fraction but lots of south windows. We are using scraps on shed and in attic

Answered by Patrick Walshe
Posted Feb 20, 2013 1:11 PM ET


$1.09/8.4= about 13 cents/R-foot material cost, which is comparable to EPS or iso at ~25-30% scrappage from window & door cuts.

Answered by Dana Dorsett
Posted Feb 21, 2013 4:53 PM ET

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