As reported here, the City of Boston, after conducting a design contest dubbed the E+ Green Building Program, selected three firms to design and build ten “energy-positive homes” on city land, which will be available to buyers for less than $400,000 (an energy-positive home produces surplus energy that’s returned to the power grid). Recently, one of the winning firms, Urbanica, broke ground on the first of these homes to be built in Boston. While Urbanica’s project achieves its net-positive status primarily through liberal use of solar panels, other innovative design features include the use of double insulation, three-layered glass windows with argon gas-filled cavities, skylights to increase natural light, sun shades, green roofs, and an energy-recovery ventilator. The energy-recovery ventilator transfers stale air out of the homes, replaces it with fresh air, and then captures the heat and energy involved in the process. The demand for these types of homes is steadily increasing and green communities – such as Allston’s new Green District – are coming into vogue. Give Mayor Thomas M. Menino and Boston’s planners an A+ for leading the way on the green building front.