Some developer-owners are building multifamily to the Passive House energy standard, paying tenant utilities, charging as if energy efficient, sending a tiny fraction to the power company, and banking the rest. Yields one hundred twenty dollars per month per apartment unit increased cash flow. See project examples at https://multifamily.phius.org/ Partial prefabrication reduces construction cost by 5%, and designing for constructability can further reduce cost by thirty-nine percent.