Green housing initiatives are taking off across the nation, with the Pacific Northwest leading the way in energy-efficient design. One vacation home in Portland, Oregon represents this trend perfectly, sending just as much energy back into the grid as it consumes, all while welcoming a steady stream of new guests.

Heated mostly by the sun and energy produced by daily household activities, the O2 Haus system is backed up with solar panels to gather power for the limited energy that it does consume. A heat-recovery system collects heat, filters the air, and disperses it equally throughout the home to offer a comfortable environment in every room without any hot or cold pockets, while a highly-efficient heat pump accommodates the water heating needs.
The house is built on a concrete slab installed over nine inches of EPS foam insulation (R-36). Inside, the walls are framed with 2 x 8s and packed with blown-in cellulose, though they are also insulated on the outside with four inches of rigid polyisocyanurate foam insulation (R-52). Triple-pane windows add to the insulation value for maximum efficiency, with remote-powered exterior shades further helping with temperature management. Custom exterior doors with Vacuum Insulated Panels complete the framework for this ultra-efficient space, which boasts an impressively low heating load of only 4,500 Btu/h.

Natural materials fill the house to further support the sustainable design. All its counters are quartz, while...