Ever since it celebrated the opening last year of zFab, its 91,000-sq.-ft. factory in Sacramento, California, ZETA Communities has been pushing hard to expand the market for its prefab construction products, which include commercial and residential structures intended to deliver high performance at relatively low cost.One of ZETA’s showcase projects, a 1,561-sq.-ft. two-bedroom town home in Oakland, had construction costs of about $165 per sq. ft. and earned a HERS Index of zero. ZETA has since dug deeper into the affordable, energy-efficient housing realm with commitments to build a number of single-family infill projects and many more multifamily communities.The first three homes of Tierra del Sol, a 22-home community in Stockton, were in fact recently completed at zFab, and the developer, a local nonprofit called Visionary Home Builders, is now fielding buyer inquires on the houses, each of which features three bedrooms, two baths, 1,268 sq. ft. of conditioned space, an attached garage, good air-sealing and insulation, and a 4.5-kW photovoltaic system that is expected to bring the performance of the building to net zero energy.About $127 per sq. ft.All 22 houses are built to the same basic design, with an R-22 floor, R-26 walls, an R-50 roof, and airtightness of about 1.03 air changes per hour at 50 Pascals pressure difference. As noted in a recent Jetson Green post, the mechanical systems include a hybrid heat-pump water heater and minisplit heating and cooling. The cost to the homebuyer for all this will be $160,000.Tierra del Sol homes are limited to buyers with annual household income of no more than 80% of the area median, and financing must come through a Federal Housing Administration-approved lender. Approved buyers also will be eligible for $30,000 of down-payment assistance. ZETA estimates that annual energy savings for each house will average $2,000.