Wooden Prefab Cabin in the Forest is Off-Grid and Passive House

Perkins&Will builds a prototype that pushes every button.

Solo House at night

Photo: Andrew Latreille / Courtesy: Perkins&Will

Delta Land Development is planning to build the world's largest plyscraper, Canada's Earth Tower, in Vancouver with Perkins&Will as architects, but that's a few years away. In the meantime, they have been keeping busy building a nice little prototype in Soo Valley, British Columbia, near Whistler. It also happens to be a gorgeous home and corporate retreat. It pushes so many of our Treehugger buttons;

It's wood. It's built out of dowel-laminated timber (DLT) made from Douglas fir by StructureCraft (we toured their factory here). This is a glue-free technology where very dry hardwood dowels are inserted through holes drilled in the lumber, which then absorb moisture, expand and lock it all together into a solid slab.

It's prefab. Because the construction season is so short, the building has been prefabricated off-site so that it could be assembled quickly.

It's built on stilts, to minimize the disturbance of the site, "reinforcing its relationship to the site as a ‘visitor,’ allowing nature and the site to remain the focus." This is an approach I have admired before; it also minimizes the amount of concrete and under-floor foam insulation; you can just wrap regular rock wool right around the bottom. I wrote earlier: "If you don't like plastic foam insulation and want to use a greener product, it actually makes sense to put the whole thing up in the air. There's also that thing we keep talking about on TreeHugger about treading lightly on the ground."

Building construction


It's Passive House. The structure is a bit confusing; there is an exterior structure of glue-laminated (glulam) columns supporting the roof and on the south face, photovoltaic panels. This wraps around an interior structure that is a mix of DLT walls and more glulam columns, which also supports a thick blanket of mineral wool insulation.

Detail of structure


This is elaborate and unusual but addresses a few of the five main principles of Passive House design: a super-insulated building envelope (two feet of the stuff), airtight construction (it's much easier to seal), and the almost complete elimination of thermal bridges (there is not much going through all that insulation except some T-joists holding up a thin layer of cladding and the weather barrier).

Interior of SoLo

Photo: Andrew Latreille / Courtesy: Perkins&Will.

Besides being the ultimate in thermal breaks, it also makes for a very beautiful interior, with all that warm Douglas fir.

view of window at end

Photo: Andrew Latreille / Courtesy: Perkins&Will.

The other two principles of Passive House design are ventilation systems with heat recovery, and high quality windows with careful orientation and shading to gather heat from the sun in winter and keep it out in summer.

Exterior south face

Photo: Andrew Latreille / Courtesy: Perkins&Will.

It's off-grid. The south face of the building is covered with solar panels. This is not optimum; one usually sees solar panels on the roof of a building, but they need them in winter here, when it could be covered with six feet of snow. There is also a pesky mountain in the way which reduces the solar gain even further.

Systems diagram


So they have lots of panels (32Kw) and batteries to run the pumps for the ground source heat pump that keeps the radiant floors warm, a mechanical room full of batteries, provision for a wind turbine if required. And just in case, a hydrogen fuel cell and some tanks of hydrogen for backup, which lets them claim to be entirely fossil-fuel free.

Hydrogen tanks
Hydrogen tanks.

Perkins&Will screen capture

They are trying so hard to make everything so perfect here, no matter what the cost, that it almost feels churlish to point out that unless that hydrogen is "green" and made through electrolysis, it is not much better than the natural gas it is made from and they are not really fossil-fuel free, but it is likely that in the future they can be.


Photo: Andrew Latreille / Courtesy: Perkins&Will.

It's Healthy. It is from Perkins&Will, which developed a Precautionary List of harmful chemicals and materials to avoid. That might be one reason they went with DLT instead of cross-laminated timber (CLT) – no glue. Two feet of rock wool is harder to work with than foam plastic insulation, but there are no flame retardants and it has much lower embodied carbon. When almost every off-grid cabin cooks with propane, there is an induction range, even though it still sucks a lot of kilowatt-hours. They have made the harder, more expensive choices, but the healthy ones.


Photo: Andrew Latreille / Courtesy: Perkins&Will

It's a Prototype. Perkins&Will writes:

"SoLo is not a typical alpine home. With Delta Land Development’s intention to pioneer a future zero emissions approach to building, we designed a prototype that demonstrates a unique approach to building off-grid in a remote environment where every choice has consequences. Performance led, the home expresses a restrained material palette while generating more energy than it uses, eliminating fossil fuels and combustion from its operation. Challenging conventions in both aesthetics and construction, the prototype acts as a testing ground for low-energy systems, healthy materials, prefabricated and modular construction methods, and independent operations intended to inform the approach to larger projects such as Canada’s Earth Tower."

My first thought was that it was a bit disingenuous to call a 4090-square-foot house in the country, that we can't begin to imagine the cost, a "prototype." It was certainly going to draw the ire of all the "why is this on Treehugger?" types.

Yes, it is big, and it is expensive. But it also demonstrates that you actually can design a comfortable home that does all these things that we go on about, from wood to Passive house to healthy. It is a prototype for the kind of systems thinking we need to solve the problems of reducing or eliminating both upfront and operating carbon emissions. Oh, and it is drop-dead gorgeous. It hits every button.