I am building a 2900 sq. ft. house this upcoming spring near the town of Carbondale, Colorado. The site is at 6700 feet and has good solar gain, which I will be taking advantage of to some degree at least. What I am trying to figure out is what type of insulation and insulated methods is going to be the best bang for my buck. I was hoping to do the spray foam, but after getting some rough estimates from a few GC's, I don't think I am going to be able to go that route. One GC said his last house that he did with spray foam in a 3100 sq. ft. house was about $25,000! That surprised me even though I knew that spray foam was an expensive route. I plan on doing at least 2 by 6 walls. I am looking for suggestions on crawl space, wall and roof insulation options. I also understand that air sealing is just as important as R factor, so I have to take into account the money spent doing that as well. I have not priced a double, staggered framed wall yet to avoid thermal bridging and increase depth, but again the cost of that concerns me. However I have not got pricing on that yet. Any advice or suggestions would be very welcome. As a few guys have suggested, I was hoping to be able to get away with using several mini splits to heat the house, so I am guessing that I am going to have to have a pretty high R factor house with a low ACH. thanks very much !

Best bang for the buck would be 1" to 2" of rigid EPS foam sheets over the wall sheathing (What kind of siding are you planning on installing?) with the stud cavities filled with wet sprayed cellulose. For the attic, I have found stabilized cellulose on the attic floor to give the most R per $. For the crawlspace, seal it up tight with with a vapor barrier product with at least 2" of rigid EPS foam insulation on the foundation walls and at the ground level. Cover the foam on the ground with sand, gravel, or a thin (~2") layer of concrete to protect it.

Open cell foam runs about 13 cents per square foot per R, installed price.

Closed cell foam runs bout 18 cents per square foot per R, installed price.

Open-blown low density cellulose on the attic floor runs about 3-4 cents /R-foot, installed.

Dense-packed cellulose in wall cavities varies with labor rates, 10 cents/R-foot is probably typical (big error bars here), installed.

Damp sprayed low density cellulose in wall cavites runs 6-8 cents/R-foot, installed.

Rigid EPS and polyiso run about 10 cent/R-foot plus installation.

Rigid XPS runs about 14 cents/R-foot, plus insulation.

Batt solutions aren't worth considering unless your installers are the Michaelango of batt installation, and you are adding exterior foam.

In your location 3-4" of EPS and 2x6 w/damp-sprayed cellulose is a good bet. You need at least R7.5 of exterior foam on 2x6 construction for dew-point control at the sheathing in US climate zone 5, R11.25 for Zone 6, and you are in the cold edge of zone 5. 3" of EPS is R12.5 at a center-foam temp of 75F, but in your climate you'll see sustained winter temps where the center-foam temp would be in the 20s, where 3" EPS will be performing at R14. But from a long term energy use point of view it's still cost-effective to go with 2 seams-staggered layers of 2" (R16.8 nominal, for Type-II EPS.) On 2x6 studs with damp-sprayed cellulose, with 4" you'd have a whole-wall R of about R30, for a wall U-factor of 0.033 BTU/hr per square foot per degree-F-delta.

Air sealing the sheathing to the studs, and doulbed stud plates to each other, and between the bottom plate & sub-floor with acoustic sealant caulk, and blower door testing/remediating the shell prior to the cavity insulation is key to getting the full performance out of the insulation you're paying for.

I was planning on doing quite a combination of siding. A very small amount of stone, a fairly large area of stucco with a pretty decent area of rusted tin and then a bit of old barnwood. Yea, four different siding materials!

As usual, Thanks Dana for the info! again and again. Thanks so much! Cheers!