The House as a System

Long cold winters are a major consideration when building on the bald ass Alberta prairie, where we live. It is not at all unusual to hit temperatures as low as -40 C for extended periods of time, sometimes even colder. Even a slight wind at temperatures that low can bite, but we don’t get slight winds- we get strong, sustained winds and sometimes dangerous gusts. A calm day around here sees winds of less than 20 km/hr, but not much less than that. Warmth in our new home during the long cold season is paramount.

Thermal mass has its benefits but is not the obvious choice for an extreme climate such as our own. It was suggested that we might choose a different building method for our home, straw-cob and straw bale being the favourites, but we were determined to go with earthbags for several reasons- ease of construction for first time builders and (very) low cost topping that list.

With that in mind, we’ve tailored our plans to accommodate the weather. The first consideration was to keep the rooms small. That in itself is an interesting concept given our propensity for big, open spaces. For big, open spaces we’ll have to go outdoors; a new habit that- to me- meshes well with our new way of life. I like the idea of spending more time outdoors and good thing, because we won’t have the power capacity to sit in front of the computer or television what with going off-grid.

Windows are an important aspect of our plan. The bulk of the windows are south facing and low in the building, to best maximize our winter solar gain. They are regular glass, as opposed to the ever popular low e variety, in order to make the most of solar heat. (And here’s one area thermal mass has the advantage, absorbing and storing the heat for slow release later.) The couple of windows (in the bedrooms) that are not south facing are low e, however, and very small. As we wouldn’t be getting much solar heat gain from either of these windows, it’s important that we minimize heat loss.

Landscape features further protect our building. The backside (north side) of the building will be bermed to near roof level, and we have plans for a surround-garden on the south side to window level. (The house itself is also sunken into the ground several feet.) The south facing garden has the additional advantage of being a slightly different zone than the rest of the property- because it wraps around so much mass- and we’re quite excited to see what we can grow.

A section of the living room has been dedicated to a greenhouse/sunspace and will be double glassed (i.e. we will have sliding glass windows on the inside of the building to access the garden). This will add to the natural warmth of the living space quite nicely, as well as extend our short growing season.

Also in the living room, we will build a rocket mass heater to wrap around the entire north wall. If you haven’t heard of these entirely efficient stoves and heaters I highly recommend you read Ianto Evans book (Rocket Mass Heaters: Super Efficient Wood Stoves You Can Build), or better yet- head to Oregon and take a course with the man himself as we did (visit http://www.cobcottage.com/ for information on courses, or to order the book). The mass heater will serve as a toasty and comfortable sitting area. If you live in a standard construction home, as we currently do, you can quite possibly imagine how nice it would be to heat your body rather than the air around you and this is one of the advantages of a mass heater. I’m always amazed at how often our heat kicks in and how cold it remains in the house- one of the (many) disadvantages of a forced air heating system.

The kitchen will house a wood stove. Not nearly as efficient as a rocket stove, but it throws a lot of heat. We are considering putting in a small rocket stove in that room as well, for days when we don’t want to use the wood stove. The plan that most interests us for the kitchen can be seen at http://cato-projects.org/ArLivre/EN/RocketStove3.htm .

Finally, there’s the roof. Admittedly, we’re fly by the seat of our pants kind of people and this whole thing has been a great big experiment- on us. So some things we’ve come to late in the game. Originally we had planned on building earthbag domes. There’s easy, cheap and require absolutely no construction experience. Roofing a structure requires a little more skill. But at this stage of the game, we are leaning towards roofing at least the larger (18’) rooms. Primarily because so little of the building is actually exposed to the elements that should we add a highly insulated roof, there really is nowhere for the heat to go during the winter. Sure, it will bleed slowly through the walls- but it’s a bleed so slow that it’s negligible. If we continue on with the dome plan, there will be considerably more space to heat and more room for heat loss.

That’s not to say that we won’t change our minds- again. We do have all winter to consider our options. If we do revisit the idea of domes though, it will be with a plan of having a second floor in each of the main domes and plenty of insulation. Another option that we’ve all but ruled out is scoria filled bags. If you live in an area where scoria is cheap or reasonably priced (we don’t), scoria is excellent bag fill for providing that little bit of extra insulation without changing your building plans.

So that’s the plan as it stands and how we intend to deal with our extreme climate. Build small rooms, sink the house into the ground and berm as much as possible, maximize solar heat gain by keeping windows on the south side plentiful, place only two windows that aren’t south facing and keep them small and low emissivity, have a sun space for additional heat gain and a nice garden area, build a rocket mass heater for the living room, use a traditional wood stove in the kitchen, and keep the roof low and well insulated. Ah, and we’ll tint the finish lime plaster a darker shade, in order to further enhance heat absorption. Our house is not simply a shelter, but a system that needs to consider and work with all components.