Image Credit: Craig Anderson
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This is the first in a series of posts by Craig Anderson describing the off-the-grid house he built with his wife France-Pascale Ménard near Low, Québec. Craig writes about the “Seven Hills Project” in a blog called Sunshine Saved.
My family and I live part-time in Ottawa, Ontario, where both my wife and I have our work, for the federal government and local university respectively. Though I’ve always wanted to live in a rural and relatively wild setting, it would be impractical for the commutes to work and the kids’ schools, as well as the isolation being too much for my wife to handle all of the time.
So a compromise was born: to rent a reasonable place in the city, and make our real home out in the countryside. It would be our full-time home for the summer, and a weekend retreat during the winter.
Building a highly efficient green home is something that I thought about for many years before it actually happened.
I never formally studied architecture or building science, but I dabbled in researching the topic for a decade. I was absolutely inspired when I first came across some of the designs for highly efficient homes from the ’70s, especially some of the passive solar designs of that time. There were terms like Trombe walls, usage of large water tanks for thermal mass, Earthships with greenhouses inside the home, and more.
There was a great deal of experimentation going on in building innovative and green homes for the future, with the hope of drastically reducing the amount of energy that it takes to both build and run a home. This experimentation really was necessary, because as I read further, I came across critiques of all of the things that didn’t work, causing things such as mold and massive overheating in the summer.
While there were a lot of interesting ideas here, clearly I was going to need further inspiration elsewhere. And I did go on to find further work on passive solar design done much more recently, that has distilled out some of the best design principles to take advantage of that free energy source, the sun.
Energy use far from the grid
More recently, I came across Passive House, another green building design philosophy that focused almost exclusively on reducing the amount of energy used in a building (Passivhaus in its original German). By focusing on energy reduction, the building envelope becomes the prime target. Massive amounts of insulation, compact shapes with a minimum of surface area, triple-pane windows, high airtightness — these are the things that allow heating (and air conditioning) loads to go way down, so low (as I read in multiple places) that a house that can be heated by only a hair dryer.
As for electrical loads, there are now efficient appliances and mechanical systems that, in conjunction with a well-built shell, bring energy consumption for space heating in a certified Passive House down to roughly 10% of that in a typical older home.
The third major strand that we needed to bring together for our project was renewable energy, so that we could build a home that was off-grid. Unfortunately (or perhaps fortunately depending on your perspective), the property that we fell in love with was very far off the beaten track, so far off that it would have been prohibitively expensive to bring in power lines.
It was going to be both cheaper and much more interesting for me to build a home that was completely off the grid. Today is a very exciting time for renewable energy, with solar panels dropping precipitously in price, new types of batteries just becoming available that are more powerful and reliable, as well as less expensive than those that came before. I am not alone in thinking that renewable energy is the future, and it is quite a ride to see that future arriving and to be a part of it.
Finally, there was the architectural style to consider. It is possible to build an efficient home in any style that allows for a relatively compact building shape, and I was drawn in particular to some of the contemporary styles. I have seen a certain style of home described in some places as “contemporary mountain” that have stylistic elements that we drew from, including a single-pitched shed roof, deep overhangs, use of lots of larger dimension wood, and a close alignment to natural surroundings.
My impression is that this style is currently most popular in the Pacific Northwest. I’d say that the single home that provided the greatest inspiration for style came from Nils Finne of Finne Architects, and a home that he built on the shore of Lake Superior.
Building site and orientation
Forest surrounds the home on all sides, with amazing views of a small valley to the south, and a back bay of the river visible about 150 feet to the west of the house. We chose a hilltop location, in large part because of the views it afforded. The other advantages of this location are excellent southern exposure for both passive and active solar, as well as it being much less buggy than the surrounding lowland areas because it was drier and windier.
That wind is a double-edged sword, however, as we are much more exposed to the whipping winds of storms and winter, which probably increase our heating loads a bit and has also put me in place to watch trees topple over and land within 20 feet of the house during a particularly vicious summer storm.
The clearing that we opened was just large enough to build the house and yard, a bit less than half of an acre. On the north, west, and south sides of the house, this means that the forest begins only 20 feet from the house. To the southeast is a grassy yard big enough to cover the septic field, and to the east is a parking area with our solar panels tucked onto the north side of the clearing to reduce the shading from the trees.
Unlike most of the homes built along the waterfront in our area, ours does not have clear line of sight to the water. We currently have a screened view of the water, which actually makes those glimpses out onto the bay more special.
Trees were kept strategically so the house would be well-shaded during the summer season, from the south and most especially against the hot afternoon sun out of the west. The best way to accomplish this is with deciduous trees, red oak and sugar maple in our case, so that all through the leafy summer season the house stays as deeply in shade as possible, while in the winter the lack of leaves allows the sunlight to stream right in. The existing larger trees at our site helped to determine where we would set the home so as to best take advantage of that shading.
Planning for the best solar exposure
The rule of thumb that I have read and been told multiple places is the house should face within 15 degrees of south to take advantage of passive solar heating, but with our site we were able to square our house perfectly to the sun. This means that at solar noon the sun shines straight into the south windows of the house.
This perfect east-west orientation gives a few unexpected benefits. One is that our entire house acts as a sundial; one can simply look at the angle of the shadows cast on the ground as the sun streams in the windows to know the time. Also, on the spring and fall equinox, we get the sunrise and sunset shining all the way across the home through the windows on the east and west sides. I noted this spring that in the downstairs bathroom (at the northeast end of the house), sunsets around the equinox are really the only time that the room gets direct sunlight at all.
Passive solar design principles suggest that a longer east-west axis is used, with windows focused as much as possible to the south side. This allows for the south wall and windows to soak up the winter sun, while minimizing the east and west faces which can heat up excessively in the summer. We doubled down on this logic by making our home a rectangle elongated east to west, with a much taller south face full of windows.
At the same time, the north side was banked into a hillside with only a few small windows; north windows are always in the shade, so they constantly lose heat through the winter. We broke only one rule of passive solar design by putting in a lot of west-facing windows, but this was a worthwhile trade-off to capture the views of the river, and trees provide good summer shade to the west.
With all of the big windows, especially in the upstairs, it certainly has the effect of bringing the outside into our home. The views change with the seasons, with veiled views during the summer and fall due to all the leaves on the trees, with much clearer lines of sight in the winter. This allows us to really soak in the valley and hill to the south, and the river to the west.
Thinning trees to best advantage
In figuring out details about the house, its orientation, and which trees to keep or cut, I spent a lot of time looking at the solar chart (above). It packs an enormous amount of information into one graph, showing the length of the day, angle of the sun above the horizon and simultaneously its location in the daily east to west motion — and does all of this for every day of the year. With a bit of measurement and calculation, I could imagine how the sun would play across the house throughout the day and across the seasons, and plan for windows, shading, and solar panels.
All in all, we have been very pleased with the siting of our home. I have recently read that there is some doubt as to whether applying passive solar principles is worthwhile in the age of superinsulated homes, but I still wouldn’t change a thing. Even though we did a lot to maximize our solar gains, we at the same time were able to meet all of our aesthetic goals, both inside and out.
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15 Comments
Agreed
I built a passive solar home a few years ago using many of the same principles you mention. While I generally agree with those that claim building air tight and with lots of insulation is very important, I totally agree with you that I wouldn't change a thing with regard to including passive solar!
Off grid solar passivehouse visions.
I am still waiting to see an off grid house which runs exclusively on PV and batteries...no generator back up. Cold climate of course, it is hardly a challenge in Arizona. There are several Canadian houses that look like they could do it with about 10 kw PV, heat pumps, and some thermal storage right now. Of course if they use a touch of wood or propane it is easy, but I want to see if the breakthrough has arrived... pure PV only. December is the only tricky month, but if the heat demand is low enough then it is possible.
Coldest months
December has minimally more precipitation but January and February at colder.
Response to Aaron Gatzke
Aaron,
Off-grid homeowners could care less about cold. We laugh at cold. The only thing we care about is insolation.
December is the darkest month -- the only with the least sunlight -- and that's why it is the most challenging month for off-grid homeowners.
responses to comments
To Ven, I would love to take this place off of propane altogether, but it just doesn’t seem feasible quite yet. I think that what it would take is for the next-generation batteries to really come down in price, so that we could store the power to make it through the longer periods of rain/snow/clouds that can occur in late fall and early winter. I plan to get there eventually, but it will have to wait a few years. Also, even the best cold-weather heat pumps currently available struggle with the coldest weeks that we get each year, as there is a stretch of every winter where the temperatures get below -25 Celsius (-10 Fahrenheit).
As for availability of sunlight for the panels, there are two different struggles. November is actually the worst month for insolation here, with the shorter days and a lot of clouds and rain. But what I’ve found is even more of a challenge is to keep the panels clear of snow in early winter, December and January. We may get snow several days a week, and if I’m not there to clear it, they can use up hours of good sunlight just to clear, and even if I do knock off the snow, I usually have to wait for the sun to take off an icy layer beneath. At least for now, I’ll be needing to keep the backup generator in good working order.
How does financing work in Canada?
Outside of some unique hard money lenders it's my understanding that in the US homeowners cannot obtain financing unless they have the ability to hook up to utilities (i.e. electricity).
Is Canada different in this regard?
Response to Chris M
Chris,
My neighbors in Vermont build a new off-grid house and obtained an ordinary 30-year mortgage from a local bank without any problems.
Financing
CMHC, which insures the majority of mortgages in Canada, actively promotes off-grid housing.
@Martin. So they have no access to electricity?
I'm only speaking about access, not actually having to be tied in.
If they have no access then good for them!
Response to Chris M
Chris,
The nearest utility pole is about a mile away, so connecting to the grid would cost more than $20,000.
It's unclear to me whether they have access or they don't have access. It comes down to money.
Off grid with no back-up
Ven, we have good friends in Minnesota who have been totally off grid for decades. They don't have a back up generator and they also charge an electric car with their system. http://geopathfinder.com/Solar-Electricity.html
reply to Craig Anderson
Yes, there must be a bunch of us off-grid that are contemplating the next leap. Batteries are one thing...dangling bunches of lithium gleaming just out of reach, but thermal storage is probably the secret sauce for cold climate space heat. Thorsten Chlupp has come close in the abominable Alaskan climate and dark winter with 5000 gallons of storage built into the house. He didn't quite make it, at 14,000 HDD but it makes 9000 HDD seem easy, especially as we actually have some winter sun below 52 degrees latitude in Canada. Once we spot a house with a total energy use of less than 800 kwh in December, we know we are in reach of the golden fruit of off-grid/no generator/ no fossil fuel. There are a few houses in Nova Scotia in that range now. Probably by 2020 we will begin to see the cutting edge appear.
Response to Jim
Jim, your friends' place in Minnesota looks great. It looks like they get the lion's share of their heating from running a masonry stove through the winter. That is a great way to heat, but only if you have the time and energy to be there to run fires basically every day. We do heat with wood when we are at our place, but unfortunately we can't be there all the time through the winter. I think that what Ven was referring to was the possibility of making all energy use come from solar panels, which would mean that it may not require constant attention. And this is where it gets tricky - I've estimated that we need something like 60 kWh worth of heat energy per day through the average days of winter. Right now this would be a very expensive thing to do at our off-grid home without using fossil fuels or wood.
response to Ven
I have looked into thermal storage just enough to see that its use is at best in an experimental stage. Based on your comment, I looked at some of the recent work by Chlupp with his 5000 gallon home storage tank. While it does in principle sound interesting, do you know if there are any data on the practicalities of these larger thermal storage systems? Costs to install, maintenance costs, reliability, lifespan of system components, etc? I also have seen that there is some other current work in seasonal thermal energy storage (as described here: https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storage). While I am happy to do a bit of experimenting, I would be more comfortable with this idea if it had more of a track record.
Reply to Craig on thermal storage.
A few thermal storage experiments have taken place in Europe, (Switzerland and Ireland) in Passivhaus single family and multi residential). Well...they work, of course. We are only dealing with a big tank of water after all, does anyone need to say "make sure it doesn't leak"?
I have a 3000 gallon in ground super insulated tank which was originally installed for use in conjunction with an outdoor gasification wood boiler. It worked great with in floor radiant heat. I now use two indoor wood stoves and get all my heat from that (10,000sq ft super insulated off grid house) However I want to begin using the excess energy from my 12 kw PV array to store some seasonal heat. I already know the system works and it is quite common to have hot water storage tanks with wood boilers, so all one does is heat with electricity rather than wood. To get a full season heat for a passivhaus at 2000 sq ft house would require storage of about 3000 kwh which could be accomplished with a 10,000 gallon in- ground super insulated tank. Of course the tank could be less if one produces in winter with PV and air to water heat pump to supplement the storage from summer/fall already in the tank. There is nothing new technically to any of this except that passivhaus is the reduction factor that was missing in past experiments with seasonal storage. With 90% reduction in heat demand, storage becomes feasible once again. The economics will vary greatly with the storage tank...but PV is also in a new low price zone now so previous dismissals have to be reviewed in a new cost light.
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