Flatpack Passive House from Detroit

Treehugger; October 22, 2015

View original release here

There are many themes and memes that we follow on TreeHugger; in design and construction, we love Passive House and prefabrication and flatpack. We have gone on about the revitalization and reindustrialization of Detroit. We're big on architectural preservation and repurposing of old buildings. We even have noted that woman managers make greener business decisions.

And now we have Phoenix Haus, a new company manufacturing flatpack prefab Passive Houses in a hundred year old former stamping plant. They are in the process of completing their first project, which has been assembled in Freeland, Michigan, 120 miles to the north of the factory.

Despite the German heritage of the company, the house is designed according to the new American PHIUS standard rather than the PHI standard used in much of the world. According to project manager Kate McDonald, that's because the new standard takes local climactic conditions into account; it gets cold in that part of Michigan. Under PHIUS, “The heating and cooling criteria are determined from formulas based mainly on local climate factors including degree-days, outdoor design temperatures and design humidity, and annual solar radiation.” It's complicated. There are other changes in the certification system in the way air tightness is calculated, which make some sense to me, and the way the certification will "now encourage inventive and creative building designs that allow for costs to by off-set by cutting edge renewable systems" which makes no sense at all because a house lasts a long time and green gizmos do not. Fortunately this house does not appear to rely on them for certification. But that is all another post; if you want to follow this rabbit hole read Martin Holladay of Green Building Advisor who dives into the issue here.

I have noted before that Passive House and modular construction were made for each other; the same can be said for flatpack or panellized construction. According to the press release,

Bill McDonald, principal of Phoenix Haus, conceived the idea of fabricating wall and roof panels in a controlled environment as a solution to the high cost associated with Passive House, when constructed onsite. “Europeans have been building these for years”, said McDonald. “I knew we could take that fundamental building science and bring it to the Midwest. Component building is ideal for the Passive House standard because such a high level of detail is necessary and can be easily accomplished in a controlled setting.”

The panels are assembled in the factory and then shipped to the site. The exterior walls are built up from 2x12s and insulated with dense pack cellulose to R-50. The fiberglass visible in the photo is only at the joints between the panels because it acts as a gasket and would not fall out like cellulose. The roof is R-70. For yet more insulation and a continuous wrap outside the structural assembly, the panels are also covered in Agepan, a wonderful all-natural substitute for the rigid polystyrene often used for this function. It is also more vapor-permeable than plastic foam; read all about it here on BuildingGreen.

This pre-built component process all begins behind a computer, utilizing powerful modeling software. With the help of a 3D CAD model, the highest level of accuracy can be achieved when designing the home. Additionally, this model was able to interface seamlessly with a CNC machine, the heavy piece of machinery cutting lumber for the home. CNC code files were created and the manufacturing process then began. Most importantly, each step taken during this progression never left the side of the aggregate energy performance model, ensuring proper performance post occupancy. After the package of wood parts was precut and finalized, it arrived to the production facility. Wall and roof panels were assembled, pre-insulated and secured with a vapor diffusion system, thereby allowing moisture to escape but not enter back through the pre-built assemblies. The panels were then delivered to the job site, assembled and secured.

Here the roof panels are being installed, supported by an impressive laminated ridge beam. In the background:

“We chose a piece of land that complimented the style of the house”, said Hilde McDonald, owner of Phoenix Haus. “The rolling hills, south facing exposure and rural setting made an ideal spot for a Passive Home.”

The house is being built by the company as a model home to demonstrate the technology:

...to bring Passive House science knowledge to the Midwest and educate homeowners of its numerous benefits. Secondly, Phoenix Haus wanted to use its innovate pre-built component system to demonstrate that the complexities and high price tag often associated with this type of home, could be substantially reduced.

Here you can see solar control in action, with the little roof overhangs over the ground floor windows shading part of them from the sun. Passive houses have a reputation for over-heating, even in winter, if you don't get the windows right. The house, designed by Sedgwick & Ferwerda Architects, is 3,234 square feet with three bedrooms and 2.5 baths. Bill McDonald, principal of Phoenix Haus, is a certified Passive House Consultant; according to the company website,

Upon passing his Certified Passive House Consultant (CPHC) exam in 2011, Bill knew he could take this fundamental building science perfected by the Germans, and bring it to the Midwest. He understood, along with the Europeans, that component building is ideal for Passive House since such a high level of detail is necessary and can be easily accomplished in a controlled setting.

Interestingly his sister, project manager Kate McDonald thinks Passive House "would be the perfect platform for which to launch an entirely new lifestyle idea based on principles of health, activity and environmental stewardship." This is something I have been writing about a lot lately, that Passive House is about far more than just about energy but about health, comfort and security. See slideshow What's the best way to sell the Passive House concept?

There are of course going to be the usual complaints that it is too big and way out in the country, but it is a model home where you really have to build what people say they want. There is also a real problem in Northern Michigan in finding trades to build those big houses in the country, and that's the market. Getting them built to Passive House standards at a reasonable price is almost impossible, so there is a real niche.

There is also so much to love about the idea of taking a ratty old closed down stamping plant in Detroit and putting people to work manufacturing sophisticated, energy efficient houses at not much more than the cost of conventional construction, flatpacked so that they can be shipped and assembled anywhere in the US. The phoenix is that mythical bird that "obtains new life by arising from the ashes of its predecessor." Phoenix Haus is a totally appropriate name for such a venture. See all our posts on Passive House here.

Kate McDonald