The Zoning Board of Appeal today approved plans for a proposed 23-unit, four-story co-op building on Highland Street between Centre and Marcella streets that would have 15 affordable units and would be designed to generate more energy than it uses.

Under Rees-Larkin Development's proposal, three of the units would be reserved for people making no more than 30% of the Boston area median income, seven at 60% and five at 100%. The remaining eight units would be sold at market rates.

The building will sit on what are now seven individual vacant lots owned by the city.

The building will have 19 parking spaces and a 900-square-foot space for art displays.

Unlike condos, which are sold like individual houses with deeds, co-op units come with shares in a limited-equity company that owns the entire building.

The proposal needed board approval because it is larger and taller than the street's zoning would normally allow. The developer's attorney, Nick Zozula, said the project warranted variances in part because of the extra affordable housing provided, in part because of the challenges of the site's topography - which rises roughly 15 feet from the street to the rear.

Board Chairwoman Christine Araujo voted for the project, but asked the BPDA to pay particular attention to architectural details that would better help the building better reflect "some of the character of that historic district."

The BPDA approved the project last month. The mayor's office and the office of City Councilor Kim Janey supported the proposal.

Highland Street project documents.