The Madrona Passive House

Design and Slope Issues

Due to the steep slope of the property, the home was essentially built as a structure on stilts. A structural slab that is supported by 26 piles drilled deep into the hillside essentially allows the home to float above the poor soils of the hillside, offering stability despite the difficult conditions. 

The home was designed for a family of four with two older teenagers. Since the children were close to moving out, the initial design placed their rooms in the basement. This area could eventually be turned into an accessory dwelling unit and help the home generate income. The home site includes gorgeous views of Lake Washington and the Cascade Mountains; a large deck was built facing the views.

The home has a 9.8 kilowatt (kW) solar array that allows it to produce more energy than it consumes routinely. During the 12-month performance period monitored by the International Living Future Institute, the home used 9,866 kilowatt-hours (kWh) while producing 10,768 kWh. This is over 900 kWh more than what was used by the homeowners. 

They also put upwards of 8,000 miles per year on a small electric car they own. They charge it with their solar panels system and still manage to live in a “net energy negative” home.

The home incorporates a heat recovery ventilator that maintains optimum indoor air quality while simultaneously allowing the home to recuperate up to 90 percent of exhaust air for further heating inside the home. 

Water—Inside and Out

In terms of water use and recycling, the Madrona Passive House has a green roof on the garage, an effective rainwater harvesting system from the main roof of the home, and permeable pavement for the driveway and other hardscapes on the property. The combination of these three elements helps to reduce the amount of damaging stormwater run-off while also mitigating erosion issues that can occur due to the steep slope. The landscape of the home is planted with drought-tolerant plants that are periodically irrigated from water captured by two large cisterns that are fed by the roof of the house.

For hot showers and laundry, the home operates a Sanden CO2 Heat Pump Water Heater that offers direct hot water and radiant heat into the home. Because passive houses tend to be particularly sensitive to temperature changes within the walls of the home, it took a bit of tinkering to find the optimum temperature settings with this heat pump. Part of the challenge in maintaining a comfortable temperature in the home was also related to manually controlling the blinds to either block the sun or let sunlight in. 

Over years of occupancy, the owners discovered the best way to keep their passive house running efficiently. Like all sustainable and energy-efficient homes, the process of living in the home reveals the best strategies and techniques for optimum performance. The owners are encouraged to continue to find ways to minimize their energy consumption.