The home rests on a gently sloping corner lot almost fully encircled by existing trees and foliage, providing privacy from the adjacent streets and neighbors. Save for the clearing required for driveway access at the southwest, this buffer was preserved. Placement of the home on the site required a delicate balance in order to remain inside the setbacks and existing tree drip line while being far enough to the north for optimal solar exposure. Digital modeling of these conditions served as a valuable tool during design. The house is oriented just 3.5 degrees west of due south. The form of the house is a main gable covering 8 timber frame bays with the double height living room bay extending out beyond the main volume as a cross gable portico. This simple structure is well suited to true timber frame construction as well as SIP panel walls and roof. The attached workshop and garage are advanced framed structures with truss roofs.
The timber frame is crafted from Douglas fir, using modern power tools to fabricate traditional mortise and tenon joints fixed with oak pegs. Each member was numbered at the factory, delivered to the site, and assembled into large bents as wide and tall as the house. Each bent was then raised by crane and fastened in place by the crew. When complete, the timber frame formed the structural skeleton for the house. Its strength and beauty are exposed to view on the finished interior.
Enclosing the timber frame are Structural Insulated Panels, made from plywood and OSB skins and an EPS foam core. These too were fabricated at a factory and then raised on site using a crane. The SIPs are 8-1/4" thick and provide R-30 insulation at walls and roof. Their joints are splined, which eliminates most thermal bridges from the interior to the exterior, a source of significant heat loss in typical houses. SIPs are extremely airtight as well, and special attention was paid during construction to seal all gaps that might leak indoor air to the outside. The tightness was confirmed at 1.7 ACH50 using a blower door apparatus and a thermal camera.
Windows are made from Douglas fir with an extruded aluminum finish on the exterior. U-0.22 triple glass with low E coating keeps heat in, and commercial quality weatherproofing keeps the rain out. The wind and rain tightness of the windows was confirmed using a pressurized hose spray for 15 minutes.
Interior finishes feature cherry flooring, cherry cabinets, and Douglas fir trim, all certified by the FSC to be sustainably harvested. Most walls are finished with integrally colored Venetian plaster that never needs painting. Ceilings in principal rooms are FSC certified Douglas fir. Flooring at the wet rooms is slate tile.
The rainwater harvesting system will meet the net zero water goal. In addition to irrigation, toilet flushing, and laundry uses, rain will also provide water for bathing, cooking and cleaning, and drinking. A 5000-gallon buried tank will store winter rain to last through the dry summer. Rain falling on the metal roofing will pass through three progressively finer filters before being sterilized with UV light to render it potable for the 80,000 gallons the family will use annually.
