Builder Hammer & Hand, based in Portland, Oregon, has developed a design and production strategy for exterior doors that conform to the Passivhaus performance standard.
H&H’s march to the forefront of in the U.S. is driven by a few factors, including the growing adoption of the standard here and the fact that windows and exterior doors for many domestic Passivhaus projects typically are imported, at relatively high cost, from Europe. The materials for H&H’s Passivhaus door – including Forest Stewardship Council-certified clear vertical-grain Douglas fir, with a polyisocyanurate insulation core – are locally sourced, eliminating the expense and environmental cost of shipping from Europe.
H&H’s workshop manager, Dan Palmer, led production of a prototype door that recently was installed on an H&H project called Karuna House, which is itself a prototype project in that it is designed to meet three stringent green building standards: Passivhaus, LEED for Homes Platinum, and Minergie-P-ECO. The project’s Minergie-P-ECO certification, in fact, is nearing completion.
The Karuna House balancing act
The Karuna House client and H&H are treating the project, begun in November 2011, as an extended case study for buildings that aim for two or more green certifications. So far, the Karuna design-and-build team has had to develop several work-arounds to accommodate materials requirements and/or prohibitions imposed by the certification programs. But the project still appears to be on track for all three. The development of the Passivhaus door adds an entrepreneurial dimension the Karuna experiment.
, Palmer notes that European homes, including Passivhaus projects, typically use overlay doors, while homes in the U.S. usually feature inset doors. The H&H prototype, at 4 in. thick, conforms to the latter style, and is designed for a double-rabbet frame, with two layers of weatherstripping. The door is equipped with a four-point lock system featuring European-manufactured multipoint locks.
H&H building energy analyst Skylar Swinford noted in an e-mail that the thermal resistance of the prototype door is about R-11, installed. The company also is working on another prototype that would feature Dow Corning vacuum insulated panels as an alternative to the polyisocyanurate, increasing the R-value at the center of the door to R-80 and the door assembly’s overall R-value to R-16. In addition, H&H will develop other options for the door frames – using over-insulated frames and low-conductivity thresholds, for example – to further boost the overall performance.
Swinford adds that prices for the door start at $4,000 plus freight.