This national report from LBNL points to the Zero Energy Now (ZEN) approach as costing about half as much while saving twice as much carbon compared to other alternative approaches. See the full report here:
The Cost of Decarbonization and Energy Upgrade Retrofits for US Homes: https://www.researchgate.net/publication/355753251_The_Cost_of_Decarbonization_and_Energy_Upgrade_Retrofits_for_US_Homes
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Xavier Walter
State Outreach
Building Performance Association
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