The accessory dwelling unit (ADU) market is alive and well in the Concordia neighborhood of Portland, Oregon.  People like these tiny structures — sometimes referred to as backyard cottages, granny flats, or laneway houses — because they can be leased out or used to accommodate an expanding family situation.  And, as these structures grow in popularity, they’re getting greener, too.  For instance, check out this high-performance ADU built by Hammer & Hand and designed by Departure Design.

This 800 square-foot structure won’t obtain Passive House certification, but Hammer & Hand used the Passive House Planning Package to plan the most energy-efficient and cost-effective approach to materials and construction.

The ADU is expected to be about 60% more efficient than a code-built home, and that’s because of details like airtight construction, insulation, and efficient ventilation.  Footers rest on geofoam and the foundation slab was poured over type II EPS.  The walls have a layer of seam-sealed plywood, 2″ of type II EPS, and 5.5″ of high-density cellulose insulation.

Inside, the backyard ADU is ventilated with a Panasonic ERV system in the kitchen.  In the same area, all of the appliances are Energy Star or better and the total project cost came in at $125,000.  It has a kitchen, two bedrooms, and one bathroom.

[+] More info on this high-performance ADU with a small footprint.

Credits: Bright Designlab.