From the architect: Site: Built on a steep slope lot in Seattle with sweeping views of Lake Washington and the Cascade Mountains, the project presented a number of challenges, both technical and permit-related. As a designated Environmentally Critical Area (ECA) Steep Slope, the lot is subject to a far more rigorous standard of review than an ordinary flat lot. Also, due to the ECA regulations, the new house had to be located within (or uphill of) the footprint of the previous house which was built on 10-12 feet of fill.
Program: The clients are a couple with two teenaged kids, looking to downsize from a large old East Capitol Hill house into something smaller and far more energy efficient. In addition to simply building a smaller house, the clients also wanted to be able to convert the kids’ floor to a rentable unit, or ADU after the kids move out.
Design: To meet client’s needs, the kid’s rooms were placed on the basement level, which is fully daylit on the north and east sides. One of the kid’s rooms with an en suite bathroom, along with the media/living area, will be converted to an ADU by adding a wall and a kitchenette down the line. The remaining basement bedroom will become a guest room, and the laundry and mechanical rooms will continue to serve the upper floors. The main living floor includes living, kitchen and dining, as well as a large deck facing the lake. The upper floor houses the master suite, office and exercise room.
To negotiate the site’s environmentally critical steep slope, a structural slab supported by 26 piles drilled deep into the hillside effectively “floats” the house above marginal soils on a “platform-on-stilts.”
Sustainability: The decision to design to Passive House standards came during the design process. By investing in sustainable site development strategies, efficient building systems and a high performance envelope, this energy efficient home project transforms an environmentally critical lot-with-a-view into a sustainable one, all while achieving the world’s most demanding building energy standard.
Structural foam insulation lines retaining walls and the structural slab to eliminate thermal bridging
High-density cellulose cavity insulation, ZIP sheathing for air-tightness, mineral wool exterior insulation board, and rainscreen of vertical cedar siding
7kW solar PV array on thermally isolated stanchion, sized to offset much of the home’s energy demand
Exterior mechanical blinds and triple-pane windows to modulate solar gain
A green roof and rainwater harvesting to reduce storm water run-off and irrigate drought tolerant plantings