Better insulation option than cellulose?
I’ll leave the specific history of my build aside for a minute and simply say my builder is trying to convince me to go with a different air sealing and insulating strategy for my house than what is explicitly spelled out in the current sales contract (dense pack borate only cellulose in walls, blown borate only cellulose in attic, and foaming the rim joist areas).
If the builder had built the envelope and framing the way he advertised and promised in terms of materials and steps to ensure super air tightness, I likely wouldn’t even be considering this. But because of how leaky the house is right now and how little confidence I have the air sealing step yet to come right before they insulate will be done well enough to overcome the issues I already see, I’m considering my options in an effort to end up with something as air tight as possible and as well insulated as possible that is a viable overall wall assembly that won’t create issues down the road…
I’m in central NC and building a house with a double wall assembly, raised heel roof trusses, etc with a vented attic currently framed but amenable to sealing it up if that makes sense. So i have 8-9 inch thick wall cavities between the 16″OC framing. Climate zone 4 technically but only a few miles from ashrae zone 3 border on the map.
Builder is offering 4.5 inches of open cell foam in the walls, vaulted ceilings, rim joists, etc and then filling in the rest of the cavity spaces with fiberglass batts (or all blown fiberglass in the attic spaces).
I’m not on board with this offer as is as that let’s him get away with a wildly cheaper overall solution than the upgrade charges I paid for the extra air sealing, closed cell rim joists and dense pack cellulose solution in the contract right now.
The idea of foaming the entire wall cavities and rim joists and all other areas to a depth of foam that gets better air sealing is appealing to me, be it open cell or closed cell foam. It would ensure better air sealing results for the house overall without having to wait for the blower door test after the house is nearly finished to learn they didn’t really air seal as well as they promised they would and now I’m stuck with whatever the results show…
In an ideal scenario, should I just plan to oversee the air sealing activities and force them to do a good job there and stick with the cellulose in the contract?
Or would doing the house entirely in open cell foam everywhere be better? If they balk at doing 8-9 inches full depth as open cell foam, how much minimum should be done to get true air seal with icynene open cell foam options?
Or should I try to get the house done with a minimum of 2-3 inches of closed cell foam (or as much thickness as possible given its higher board foot cost and my current contract allotment for the insulation) and then finish with fiberglass batts or netted and blown fiberglass?
The builder’s primary insulation contractor doesn’t do cellulose. So the builder has likely lied to me from day 1 and always planned to try to pull this crap no matter what he signed on for in our sales contract. So part of me wants to force the contract to be honored and do the dense pack cellulose. But if I can get an even better performing wall assembly and better air sealing overall than what I expect if i force the cellulose, I’m willing to explore it and make the builder pay for it after all the things he has been pulling for the last 2 years on this house build…
Thoughts? Thanks in advance 🙂
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