Trying for R40/R60 in Colorado (zone 5)
Sorry if this is in the wrong category, I’m a newbie.
Hi all. My partner and I recently purchased 2.5 acres in the Denver area. We’re in the final design stages of the modern efficient home we would like to build.
We are GCing/self-building this home. It’s our first, but we’re leveraging the experience of my FIL, who has built about 8 homes himself. We decided to use the “family” architect, who has been receptive and great to work with but may be old school.
I’ve been heavily researching the PGH philosophy for about 9 months now. We’re at the stage of deciding what to do about insulation and I’m getting the feeling that my ideas are somehow atypical despite being commonplace in the green building world.
I put my foot down on no spray foam…we don’t want to be responsible for that environmental impact nor the amount of VOCs in the house.
I initially proposed (inside out): painted drywall>Rockwool batts (2×6 studs)>Zip sheathing>4″ recycled polyiso>furring strips (rainscreen)>siding. Similar design for the roof, we’ll have a vaulted rafter section where we’ll use 11″ batts or cellulose and the same recycled polyiso. Total wall: R-40, total roof: R-60+.
He immediately balked at this as it seems to be very nontraditional for the region. He was also very concerned about the 3 “trips” raising construction costs astronomically. He also pointed out we will have a large 6-panel bifold patio door, so exceptional effort might be wasted.
His proposal is (inside out again): painted drywall>batts/cellulose (2×6 studs)>Zip R-3 sheathing>siding. On the roof he’s suggesting: painted drywall>cellulose/wool batts in the trusses and rafters>OSB>6″ thick polyiso bonded to OSB>ice and water shield>roofing. Total wall: R-20, total roof: R-60+.
I’m not sure what I’m asking but is it worth combining the sheathing, exterior insulation and furring steps into one trip at a loss of significant insulation value and rain screen? Am I way overthinking insulation for our high desert climate?
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