One goal of ZETA Communities, the San Francisco-based designer and manufacturer of energy efficient prefab buildings, is to produce 2,800 housing units by 2013. It is an ambitious target, given current economic conditions, but ZETA is forging ahead.In September, at a former Air Force hangar near Sacramento, California, the company completed the conversion of the facility into zFab, a 91,000-sq.-ft. factory that currently handles all its production. One of ZETA’s model homes, a 1,561-sq.-ft. two-bedroom townhouse in Oakland, California, has attracted substantial attention, including positive comments from GBA Advisor Ann Edminster, who toured the completed house in February. And last week, the company announced it had secured $5 million in financing from Black Coral Capital, a private equity fund specializing in the clean-tech sector.Modular and relatively low-costTo date, the company – in collaboration with various developers, public agencies, and suppliers – has committed to design and build more than 130 housing units. One recently announced example is now in the entitlement phase: a 30-home infill development in Sacramento that ZETA says will target median and low-income customers. Called 2500 R, the project is being pursued by ZETA in partnership with Pacific Housing Inc., a nonprofit specializing in affordable-housing services. The homes will include solar-power installations and are being designed to operate at net zero energy.ZETA and Pacific Housing have attracted support for the project from the Department of Energy’s Building America consultants, mechanical engineering and energy efficiency specialist Davis Energy Group, and the Sacramento Municipal Utility District’s Home of the Future program and SolarSmart initiative, which offers rebates for solar installations on homes that meet the program’s construction standards. The first few 2500 R homes are expected to hit the market by the end of the year. ZETA told the Sacramento Business Journal that the project’s 1,400-sq.-ft. two-story homes have been tentatively priced at $315,000, or about $225 per square foot, including land, foundation, and site work.If the performance of the townhouse in Oakland is prologue, this could turn out well. The townhouse, assembled with four factory-made modules, came in at $165 per square foot, excluding land, foundation, and site work. And as Ann Edminster notes, it achieved HERS 0 rating.