When a couple from Santa Cruz said they wanted to “push the ecological envelope,” architects David Arkin and Anni Tilt thought a straw bale house could be just the thing. But the architects didn’t stop there. Their clients needed enough room for four kids, and they hoped to include a space that could be rented out for additional income or for aging parents to come live. A sprawling manse was exactly what the clients didn’t want, so Arkin and Tilt built a house with a compact plan and an energy-smart, low-impact sensibility. With four bedrooms, an office, and a one-bedroom apartment with its own entrance, the house measures 2,500 square feet total. For a family of six, that’s modest.

Abundant natural light, fluorescent and LED lighting, and Energy Star-rated appliances keep energy use minimal. When extra is needed, a heat pump kicks in hot water for space heating and domestic use. This usage is in turn offset by photovoltaic panels on the roof. Another thing: There’s not a fan or an air-conditioner in sight. That’s because the windows—especially the ones in the dining room that are two stories high—provide natural ventilation. Recycled and salvaged doors, interior windows, flooring, and driftwood pickets reduce environmental impact. They give character, too, and the sense that a house like this one is especially at home in Central California. For a closer look, check out the slide show.

Learn more about markets featured in this article: Santa Cruz, CA.