Balancing embodied & operating carbon – wall assembly
I’m building an apartment building in Minneapolis (climate zone 6) trying to balance three goals: 1) minimize the embodied carbon of the building 2) minimize operating carbon emissions and 3) make the pro-forma work.
The building will be all electric (mini-splits for heating/cooling) with a solar array sufficient to meet the needs of all six units.
The originally specified wall assembly was 2×6 studs @ 24 OC, dense packed cellullulos in wall cavity 1)and 3″ of continuous GPS exterior insulation.
Question: Which assembly would you choose given my goals?
In the midst of value engineering with the builder, it looks like I need to drop the GPS all together. The proposed wall assemblies (cost equivalent) are:
1) SIPS using FSC certified plywood and GPS insulation achieving R29
2) Stick framing with T-Studs and dense packed cellulose (R20/21)
Option 2 has lower embodied carbon by quite a bit, but has 30% lower R-value than the SIP assembly. That said, the building will be heated/cooled with solar power…so the lower operating efficiency doesn’t result in more carbon emissions.
I don’t have the knowledge, team or extra budget to pay someone to actually calculate the expected trade-off in carbon….so would love the community’s thoughts on this dilemma!
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