I have been trying to cost out several styles of building but mostly stick built, SIP roofs and ICF. It's not easy to get actual prices for comparison.
About the only thing I can say is that foam is expensive. I think what I have arrived on for a roof is I-joists sheathed with ZipR insulated OSB that also has a water barrier coating. I will use plenty of Zip tape and liquid flashing to get a water and vapor impermeable roof deck, then add a radiant barrier, air gap and standing seam metal roof. The ZipR sheathing will add some insulation with it's foam layer, create a thermal break between the deck and I-joists and should make for a good water/vapor barrier. This seems a lot cheaper than plain OSB with a separate water/vapor barrier and an inch of foam sprayed underneath and a whole lot cheaper than going thick with the spray foam. Under my ZipR, I want to do a "blown in blanket" insulation that is a lot cheaper per R value than foam so it will let me get around R50 without breaking the bank.
You could do similar construction in walls and be a lot cheaper than foam but not as high R value if you only have 5.5" of wall to fill.
I was going to go that way but the more I looked at ICF vs the stick built wall I wanted with metal siding, exterior foam and peel-and-stick water barrier, the ICF seemed just a little more expensive but it's easier to make a really tight envelope, it is easy to make it insect resistant, it will never rot and some types can be nearly fireproof. Since my living area is going to be attached to my garage/shop space, fireproof is great for me. I think it is worth the premium because stick built just doesn't last as well as concrete. I expect mine to be standing in 200 years and if someone wants it gone, they are going to have a big job ahead of them. A stick built home can be around 100 years later (I'm currently living in a house that's about 102) but they have issues, lots of issues.
I'm going to go to great lengths to make my home/shop perfect for me and as future proof as possible because it should be around for a very long time.
Resale value is also an issue. With a stick built home, I don't think metal siding or peel-and-stick are going to move the needle much but ICF could. It's going to be built like a vault.
The math could be different where you live.
I am waiting to start building because of the time it will take to get permits, I should be starting in about a year. If you can wait, those wood prices should come down and DH might be healed up, that will change the math.
I am planning to do as much of the labor as I can with minimal help except for site work and concrete. If you can avoid paying a crew, that is probably a lot more savings than the difference between stick built and ICF.
Good luck. |