Leaf 3 Is a Tiny House Designed for Seriously Cold Climates

It's probably a real test of character, living in 97 square feet through the long, dark Yukon winter in Pelly Crossing, three hours north of Whitehorse. It's also a real test of design and construction; the temperature gets down to -50°C (-58°F).

A few years back Kim showed Laird Herbert's Leaf House and I admired its aesthetics and roofline; Now, with Leaf version 3 he has taken the concept to a whole new level of technical sophistication.

Reducing the Weight of the House

It's a simple interior, with a Murphy bed instead of what has almost become a standard, the loft bed. This allows for a smaller volume and lower ceiling, and helps reduce the weight. In fact, weight has become a bit of an obsession here, and the house weighs less than 5,000 pounds. This is really important if you are going to move this a lot. It is also hard to do if you are building for this kind of climate.

So to keep the weight down, the cladding is simply galvanized mesh normally used to reinforce concrete; it acts as a rain screen and is a lot lighter than conventional siding, although to me it doesn't look like it is going to a whole lot of rain screening. It's installed over lightweight foam sheathing and metal x-bracing that stiffens the 2x3 framing.

Insulation

For insulation, Laird uses vacuum insulated panels that have an R value of R60 per inch; he puts R68 in the floor and roof and R38 in the walls. Panasonic explains how they work:

Wrapped in laminate film to create a low vacuum inside and control thermal conduction, our vacuum insulation panels use a proprietary lining molding technology coupled with improved insulation performance of the lining to boost overall insulation performance to the level of a full-vacuum thermos despite the low-vacuum environment. This major improvement prevents energy loss from heat transfer in house-hold and other appliances.

So basically, the occupant of the tiny house is living inside a thermos bottle. Someone cooking, showering or just breathing in such a small and tight space is going to generate a lot of moisture which could lead to icing and mould even with quadruple paned windows, so some form of fresh air supply is going to be required. A heat recovery ventilator would be the best thing, but they have ductwork and are pretty big and this space is very small.

But Laird finds the Lunos E2 HRV, which is like one I have never seen. It doesn't have two sets of ducts; Instead it has a ceramic core that absorbs the heat from the air as it is pumped through by the fan. Then, after 70 seconds, the fan reverses and brings in fresh air, recovering 90.6% of the outgoing heat. It's almost silent at 16.5dB and sips electricity. This is a wonderful technical advance for getting fresh air into small, tightly sealed homes and apartments.

Being so well insulated, the tiny house doesn't need a lot of heating; In fact, all it has are two radiant electric panels totalling only 800 watts. We're talking a hair dryer here, turned to low. The whole house can operate on less than 15 amps, what you get in one circuit through an extension cord.

The Kitchen

The kitchen has a compact fridge and freezer, and an interesting countertop:

Using a concrete micro-topper and foam backer board, Leaf House was able to create an ultra-lightweight concrete countertop for version.3, which gives the appearance of a slab of concrete but weighs below 35lb.

The Bathroom

The bathroom is supplied with hot water from a 30 gallon tank with a "ventless tankless propane water heater," and has a custom bucket toilet. These seem to be almost standard in tiny houses now. But composting toilets almost all have exhaust fans which will create all kinds of problems. It will be really interesting to see how this works out over the course of a winter.

This has been designed for perhaps that harshest climate that any tiny house has seen, it's colder than Mars and not much more hospitable. Laird has juggled weight, moisture, insulation, wall thickness, rigidity and electrical consumption. He has used FSC certified woods, reclaimed materials and healthy finishes. It looks cosy and comfortable too. It is going to be occupied by an instructor at the Yukon College Campus, so at least it won't be in the middle of nowhere, but I suspect wintering in 97 square feet will still be a real challenge.

More at Leaf House.