The key innovations

Poured-earth walls create a patterned effect and add insulation. The multihued layers of earth turn the stair wall into a natural mural.

The well-insulated roof is supported on ready-made curving laminated beams. The lower section, which extends into the interior, has galvanized metal roofing and an interior light shelf that reflect low-angle winter sunlight onto the curving ceiling and deep into the living space.

The 3-kilowatt photovoltaic array is tied into the electric company’s grid, allowing Frerking to sell excess solar-generated energy to the local utility.

An attached sun space on the lower level collects heat for growing fresh vegetables, while heating the main floor mass from below.

A heat-recovery ventilator mixes outside air with captured heat or cool air, so fresh air is provided without compromising energy efficiency.

Native and drought-tolerant plants are used for landscaping.

Low-cost precast concrete tiles are set in sand over a standard membrane roof to create exterior decks.