Passive House Case Study: Issaquah
The Passive House building standard is the most rigorous in terms of energy efficient design. It leads the industry in both Europe and North America. We recently had the opportunity to check out a passive home during its construction thanks to our friends at Sunshine Construction in Washington state.
The project was a 3,800 SF single family residence located just 20 minutes from downtown Seattle. Nested on the side of Cougar Mountain, the home is in the middle of a forest and has picturesque views of Mt. Rainier. The house was designed by Velocipede Architects and is being built by Jon Alexander, a veteran in green building and the owner of Sunshine Construction. Jon is the real deal in terms of competence and ethics. We timed our visit to view the siding installation. We were there to see vertically-installed black Gendai™ going up over a rainscreen on the exterior walls. Standing next to the house is a large, detached garage, also clad in black Gendai™. While the garage isn’t being built to Passive House specs, it’s still going to be extremely energy efficient.
Jon comes from a family of homebuilders going back four generations and has been an environmental activist since the age of 16. He majored in environmental studies during college. Wanting to bridge the gap between his activism and his family’s line of work, Jon started in green building in the early 1990’s. Fast forward 30 years, he’s now a singular authority on Passive House construction in the Pacific Northwest. To keep the most rigorous standards Jon only manages one project at a time. His projects are meticulous and he is highly sought after.
Throughout his 39 years in the industry, Jon has seen product trends come and go. With sustainable building materials longevity and lifetime carbon footprint are key. Jon’s learned to be skeptical of new products and vets them rigorously. So when it came to the Issaquah project (Jon’s first time using shou sugi ban), he’s been pleasantly surprised with the results. Shou sugi ban is designed to last 100 years or more without maintenance, longer if reoiled periodically. Jon builds his homes to last 200 years or more as a basic design and construction parameter. Shou sugi ban matches this parameter by either being replaced once during the structure lifetime, or being maintained periodically like other wood siding to last the entire structure lifecycle.
What is Passive House design?
Passive House is a construction concept rather than a brand name. The aim of Passive House construction is to build environmentally friendly homes with an emphasis on comfort and affordability. Building a Passive House does cost around 8-12% more than a standard house upfront. The payoff is in the dramatically lower utility bills. Passive Houses generally use 90% less energy than a standard house.
Controlling air seepage is a defining parameter in Passive House construction. Air tightening is the most important aspect of Passive House construction. To be a certified Passive House, the amount of air seepage must be at least five times lower than that of a standard home.
An airtight house might not sound appealing. Add in multiple occupants, some pets, some garlic and onions, and the thought of an airtight house may turn you off from Passive Houses altogether. Despite the terminology there is actually a constant, fresh supply of air delivered into the home. Part of Passive House design is the use of heat recovery ventilator (sometimes known as energy recovery ventilator) systems. These systems supply fresh (and purified) air to the interior of the home, keeping the temperature comfortable and free of pollutants. The system also transfers water vapor which prevents the air in the home from becoming dry and stale.
Thermal Bridging and Passive House Design
Another big concern in Passive House construction is eliminating the presence of thermal bridging. Thermal bridging refers to any area in the house which transfers heat from one area to another. Thermal bridging is undesirable because it reduces overall thermal performance. As such, the windows and doors in this type of building must be specially designed. The windows used on Sunshine Construction’s house are specialty and were imported from Germany. They’re triple paned at 3/4″ thick each. For reference, the majority of standard homes use windows with a glass thickness of 3/32”. They’re super heavy and super hard to maneuver. But they are well worth the extra effort and expense since the long term payoff due to energy efficiency is fantastic.
More Energy Efficient Home Options
When it comes to building an energy efficient house there are several standards and practices available. Virtually all other standards will have less stringent code than those of the Passive House. Net Zero is an option that relies heavily on the use of renewable energy sources rather than on passive build practices. If you’re looking for something similar to, but not as rigorous as a Passive House, a Pretty Good House is a similar concept. Pretty Good House has a stricter code hurdle than is standard in North America. However, it only goes so far as to make efficient financial sense.
Not everyone has the tenacity to build a home, let alone one that adheres to the most stringent standards in the industry. Sustainability and efficiency standards make the world a better place. John’s dedication and work in Passive House design and building for nearly 40 years shows incredible dedication to his clients. We are very proud to have our yakisugi included on this project. Stay tuned for the next update on John’s Issaquah project – we can’t wait to see the finished result!
To learn more about Jon and Sunshine Construction, click here.
To learn more about Passive Houses, click here.
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