This four-story apartment project in Portland’s Munjoy Hill neighborhood is one of the most high-tech buildings in Maine. It produces 9,600 kilowatt hours of solar electricity annually, uses air source heat pumps, a heat recovery ventilation system, and solar thermal hot water. With three units and over 4,500 square feet, there is no furnace required. This is a net zero home designed and built by Portland’s Kaplan Thompson Architects and Mike White of Island Carpentry. The building is very air tight; the outside walls are more than 9 inches thick, keeping the heat in for the winter and the hot air out in the summer. The building’s air source heat pumps provide heat in the winter and cool air in the summer months while the ninety hot water tubes on the roof of the building, provide hot water to three hot water tanks (one for each unit) and the back up to the hot water tanks is solar. Since the solar electric panels offset all the building’s electrical needs, there is no oil or natural gas in this building (the only propane used is for the kitchen stoves, a personal preference of the building owners).