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Cost Comparison: Spray Foam vs. EPS foam

ryanl75 | Posted in General Questions on

Hi. I’m guess this has been asked plenty of times but I couldn’t search the q&a.  I’ve always been interested in energy efficiency but this site has really got me motivated.  I’m having built a Zone 5, 28×32, slab on grade home and would really like to go with 2×6 w/batt or cellulose then 2” ext eps/XP’s foam.  Does anyone have a ball park cost (per sq ft)”?) on the costs of this vs just 2×6 or 2×6 with spray foam.  It would help me a ton so I can better plan my conversations with the builder.
thanks! Ryan

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  1. user-1072251 | | #1

    I'm not familiar with the current costs of spray foam so I cannot answer your direct question, but the larger question is which will work better in your home. A large amount of the heat inside your home is lost through 'thermal bridging" - heat traveling through conductive materials - like wood - from the inside to the outside. Spray foam, or any other type of insulation filling your stud bays - has -0- effect on eliminating thermal bridging. And, the studs in your wall amount to 20-25% of the total wall surface, so it matters. Polyiso has a higher R value than EPS, but either would be better than a higher R value in the wall cavities.

  2. ryanl75 | | #2

    Thanks for the reply. As you said I’d really like to insulate to reduce the thermal bridging. I’m anticipating a high cost going that route from some very initial talks with my builder. We have a quote of An additional $3900 for adding 2” of spray foam to the 2x6 wall (on the interior) and a ball park number of $7000+ For a 2x6 with batt and 2” exterior. Those are materials and labor costs in addition to my original planned 2x6 batt Only wall. So Im just trying to work my way through the costs of each route and was hoping someone might have some ballpark numbers. In my mind also is whether I might pay a bit more using a builder who hadn’t built with that method before. From many of the gba articles spray foam is usually said to be expensive but there wasn’t a good reference comparing it to other “pretty good” methods. Thanks for the wonderful site. Very informative

  3. user-1072251 | | #3

    In my area, 2" EPS (R-8) is $12.50 a sheet. (It's the unfaced white coffee cup stuff) While I dislike fiberglass for many reasons, and prefer either dense pack cellulose or Rockwool batts, fiberglass would probably work, it's relatively inexpensive and the combined R value is probably higher than the spray foam route. We buy it at a commercial roofing supply; it seems to be hard to source elsewhere. We use 1x3 spruce strapping screwed through it into the studs, and the siding is fastened to the strapping. Slightly more work, but it's lightweight and fast to install. Since you'll get the most bang for your buck by making the house air tight, use taped ZIP or permeable Henry peel and stick on the sheathing.

  4. soarak | | #4

    In regards to spray foam. Please google some issues people have had with improper installation of spray foam. There is a good video on CBC, but I could not find it. I found an article though.

  5. ssnellings | | #5

    What state are you located in?

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