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Solar Home on Capitol Hill (Seattle, WA, USA)

This project's most visible green feature is the array of photovoltaic panels and solar-hot-water collectors mounted atop the penthouse roof. The PVs can produce 3,200 kWh of electricity per year, and, with the help of assorted energy-saving strategies throughout the house, they provide a significant portion of the owners' energy needs.

Follow the link to an in-depth case study of the project designed by Blip Design Architects, provided by USDOE's High Performance Buildings database.


Vacuum-tube solar-hot-water collectors supply water to a storage tank, reducing or eliminating the need to heat water with gas. Wastewater heat-recovery coils wrapped around the shower drains further reduce the need to heat water by exchanging heat between the water running down the drain and the supply water.

The house is heated by a hydronic radiant floor. The only mechanical ventilation in the house is that required by the energy code for whole-house ventilation. The fresh-air intake is located in the basement server room. The computers in the room preheat the air entering the house and, in turn, the fresh air cools the computers. The required upstairs ventilation fans are oversized to act as the whole-house fan.

All of the lighting in the house is fluorescent or low-voltage. There are no line-voltage incandescent fixtures in the house.

The photovoltaic (PV) system can produce up to 3,200 kWh of electricity per year, supplying a significant portion of the owners’ energy needs. The PV system is tied to the utility grid, and the owners have a net-metering agreement with the local utility.

The house boasts a super-tight, super-insulated envelope. Blown-in, low-density, open-cell foam polyurethane insulation insulates to greater than R-30 in exterior walls and R-45 in the roof. The professionals who performed the blower-door test said it was the tightest house they’d ever seen.

Because the remodel did not add to the home's footprint, opportunities to improve the orientation and massing were limited. The interior was opened up considerably to allow natural light to penetrate all areas of the house. The penthouse and roof terrace allow the owners to enjoy the outdoors and views in any kind of weather.

Energy security

The house has a “smart” whole-house monitoring system, in which the major systems are interconnected. It serves the lighting, electrical, HVAC, audio-visual, and security systems. This interconnectedness increases the home's efficiency. For example, the motion detectors for the security system sense when a room is occupied and adjust the lighting accordingly to save electricity. Ventilation can be adjusted to room-specific needs through the system, which uses the VNOS/CEBUS protocol.

Grid-tied photovoltaic modules on the roof generate electricity for net-metering, but storage batteries provide electricity during power interruptions.

With one or two exceptions, all of the windows in the house are operable.


Green Strategies


  • Wall Insulation
    • Achieve a whole-wall R-value greater than 25
    • Add blown-in or sprayed-in insulation to existing walls
  • Daylighting for Energy Efficiency
    • Design an open floor plan to allow exterior daylighting to penetrate the interior
    • Locate floor openings under top-lighting to increase daylighting penetration
  • Non-Solar Cooling Loads
    • Provide high-low openings to remove unwanted heat by stack ventilation
    • Use operable windows
    • Use a whole-house fan for night cooling
  • Water Heaters
    • Use solar water heaters
  • Photovoltaics
    • Use a photovoltaic (PV) system to generate electricity on-site
  • High-performance Windows and Doors
    • Optimize energy performance of glazing systems
  • Luminaires
    • Use luminaires that accommodate compact fluorescent lamps
  • Air Infiltration
    • Perform blower door testing
  • Ventilation Systems
    • Draw supply air from favorable microclimates around the building
  • Lighting Controls
    • Use occupancy sensors
  • HVAC Controls and Zoning
    • Use occupancy-based conditioning controls
  • Roof Insulation
    • Achieve a whole-roof R-value greater than R-35