The president of the San Francisco Board of Supervisors says that he will propose a resolution requiring all new buildings in the city, both residential and commercial, to include rooftop photovoltaic (PV) arrays where feasible, SFGate.com reports.There is “potential for sustainability on every single roof in the city,” David Chiu said. He called for PV arrays, rooftop gardens, or both on all new construction in an initiative called “Solar Vision 2020,” which would simultaneously reduce greenhouse gas emissions in the city and benefit the solar industry.Chiu acknowledged that might not be practical on all buildings. HVAC equipment can take up a lot of space on the roofs of high-rise towers, for example, and some houses don’t lend themselves to rooftop PV installations.“Certainly for commercial buildings we believe this is absolutely feasible,” he told SFGate. “If it were up to me we would do it on larger residential [buildings] and then see what’s possible on smaller residential. But at this point we need to get the conversation going.” Solar Vision 2020 has broad goalsChiu’s proposal contains several other provisions:A San Francisco program that helps homeowners and business owners pay for the installation of solar panels, now scheduled to expire in 2018, would be made permanent.By the year 2020, the capacity of PV installations in the city would double, from its current level of 26 megawatts (MW) to 50 MW.PV arrays with a combined capacity of 2 MW would be installed at “tenant-occupied residences” each year.The director of the Housing Action Coalition, Tim Colen, didn’t argue with the intent of the initiative. But he said that California already has the toughest standards in the country for new construction and that Chiu’s plan could increase construction costs “at a time when we’ve got a crisis in affordability,” the web site reported.