Hey everyone, Some of you know im about to build a house in northern Maine on a insulated slab and now im starting to think about my walls. Got a quote on having someone foam it and the estimate almost knocked me out. My budget is tight but im trying to take the time to do what i can in finding a way i can insulate this home well and keep my wallet in check as well. I could foam it myself (walls) for about $4300 using the estimater at sprayfoamkit.com Or i thought about fiberglass (yuk) and putting two layers of rigid foam on the exterior. Im just lost in making good insulation decisions. Any advice out there?

blow in a R49 or somthing in ceiling? Sigh tough decisions are worse when the budget dictates alot of it.

We'll need a better description of your wall assembly to give reasonable advice.

DIY foam kits are pretty expensive at high-R, and are easy to screw up with on larger projects. (Temperature control of both the chemicals and the surface you're spraying are critical to getting good results, and hacking the stuff out for the re-do is an expensive PITA.)

Double layered rigid polyiso over the exterior sheathing on high-density batt insulated framed walls can be done at reasonable cost. 2x6 24" o.c. framing w/R23 rock wool plus 4" of exterior polyiso comes in at ~R40 after thermal bridging. If you can get reclaimed roofing iso from commercial building re-roofing/demolition it can be cheaper than batts. (insulationdepot.com or other- I have multiple vendors in that stuff near me advertising on craigslist.)

Double studwalls and dense-packed cellulose is usually more cost effective if you're looking for super-high R.

Air-sealing the structural sheathing with acoustic sealant caulk is a heluva lot cheaper than spray foam.

keep in mind the house has to be designed for the extra insulation; at least to do it with the least expensive methods.

You'll probably find that foam is the most expensive way to insulate your house. Fiberglass is the cheapest, but it doesn't actually work well. The least expensive commonly accepted method is double walls insulated with dense packed cellulose or fiberglass. I'd suggest aiming for (2) 2x4 walls with a 5" space, so you'll have 12" of insulation.

Hello:

I have almost finished my house and I used Roxul insulation - See: http://www.greenbuildingtalk.com/Forums/tabid/53/aff/22/aft/81782/afv/topic/Default.aspx

It cost $2,173 for about 1340 sq ft (gross) of wall space.

R-30 total. (Not whole wall R-value)

Rob.

IMO, it's pretty hard to beat cellulose plus a couple of inches of EPS foam.