Completed Rammed Earth Walls. Awaiting doors, windows and roof.
On a clear, sunny day in mid-October, I accompanied Terrell Wong, of Stone’s Throw Design, to beautiful Northumberland County to meet Sylvia Cook. Sylvia was building a rammed earth home and Terrell was the architect. I was intrigued by the idea of a rammed earth home and as I’ve mentioned in a previous post, it’s a lot different looking than I thought it would be. I’ve described the building and the technique in that post, but I was also interested in what made Sylvia decide to build such a remarkable dwelling in the first place. I asked Sylvia a few questions about her motivation and what the future holds, below are her answers:
1. What were the factors or influences that led you to want to build a sustainable house? And, what helped you to determine that rammed earth would be the most sustainable material?
Sylvia: Some years ago I had the pleasure of hearing Gywnne Dyer speak and found myself in agreement with his assessment that the biggest threat to global security had little to do with terrorism or even traditional wars, but everything to do with climate change. He provided convincing evidence that climate change would kill millions of people, impoverish hundreds of millions more, disrupt cultures, foster terrorism and cause wars. And all we really need to do to prevent this is eliminate our dependency on fossil fuels, something we will have to do sooner or later in any case as the supply is limited.
I’ve been interested in sustainability long before the phrase had been coined. I believe it was “caring about the environment” back in my day, but I like the concept of sustainability, defined as what it will take to sustain the planet in such a manner that humans can live on it in comfort. It had long been my hobby to research and design the most sustainable house possible, and I had looked into straw bale, log homes, earthships, cob, adobe, ICF, glass bottles, geodesic domes, and a number of concepts using recycled materials. When I came upon rammed earth, I realized it met all of the criteria I had come to associate with sustainability:
- locally available, abundant material – appropriate subsoil is found everywhere, a very small (five acre) pit would provide enough leftover material (after the gravel had been extracted) to build 5000 homes
- does not deplete any natural resources – we currently clearcut over a million acres every year in North America to build houses. Even strawbale depletes the topsoil.
- non-toxic – there is nothing organic in rammed earth hence nothing for moulds to grow on and no need for chemicals to combat moulds or fungi in the building materials. Nor are there any other chemicals needed: no paints, drywall compounds or plastics.
- beautiful in its unfinished state – if a building is not beautiful, no on will want to live in it and every added step of finishing requires more energy to process, transport and apply.
- durable – rammed earth has stood the test of time: the Great Wall of China is only one of many ancient examples from all over the world. Modern rammed earth, stabilized with rebar and a small percentage of cement, should easily last hundreds of years, eliminating the stream of waste as houses need repair and replacement. Stabilized rammed earth is impervious to fire and able to withstand hurricanes, floods and earthquakes.
- energy efficient – the most important aspect in my view. In the occupancy stage, representing the vast majority of a building’s energy use, rammed earth truly shines. The enormous thermal mass of the walls allows them to absorb and retain solar energy from south facing windows. The house will literally heat itself and, if properly insulated, will stay warm. In the summer a large overhang ensures that the walls stay cool. Add a few solar panels and the house is net zero energy, for every one of its five hundred plus years. If every house on the planet were built of rammed earth we could cut our fossil fuel use in half.
- feeds the human spirit – there’s something about rammed earth that makes it very calming. Perhaps it is the solidity of the 18” walls, the natural surface, the quiet of the building, or some less definable quality. If architecture is going to improve the human condition, rammed earth is an excellent starting point.
First and second floor, pre floor installation
2. How important is thermal mass of a building in your decision?
Sylvia: When designing a passive solar house (which is a house heated by the sun shining through the windows) the challenge is always to store the energy. Any house will warm up when it’s sunny, usually too much, but cools down quickly when the sun is gone. Older heat storage solutions included concrete floors, Trombe walls (a thick wall just inside the south windows, blocking the view), rocks, water (in pools or bottles in various locations), underground tunnels, etc. Rammed earth walls give ample thermal mass acting as a huge heat sink. A typical stick frame house has one or two tonnes of mass; 50 – 100 tonnes is considered the minimum necessary for heat storage. In our construction the 6” of insulation in the middle of the wall leaves 6” of rammed earth in the interior of the house, plus the two 18” uninsulated interior walls, yielding 530 tonnes of thermal mass.
3. How labour intensive is it to build a rammed earth wall?
Sylvia: It is certainly more labour intensive to build rammed earth than standard building methods. The majority of the cost of building rammed earth is labour; the material is “dirt cheap.” But why is this a bad thing? Is it preferable to spend money on toxic, energy intensive, highly processed materials or to provide a living to a group of generally young people interested in making a difference in the world?
Natural waves in the walls due to the layering of the dirt mixture
4. What will be your primary heating source?
Sylvia: The sun. (See #2.) The Ontario Building Code insists on some form of heating so we’re installing baseboard heaters as the cheapest alternative but expect that they’ll almost never be turned on. We investigated geothermal and various in-floor systems but just couldn’t justify the expense for the small amount of heat needed.
5. How do you install the second floor, which from the photos, doesn’t exist yet?
Sylvia: There will be ledger boards anchored to the walls with epoxied-in threaded rod. The joists will hang from the ledger boards, just like building a deck. I’ll send pictures of the process if you’re interested.
6. You have a lot of window space in the design. How are you dealing with the contradictory goals of maintaining a constant comfortable temperature within the house, while allowing for natural light? In other words: most windows are the weak points of a home’s thermal envelope — why do you feel they won’t be a significant issue affecting your home’s interior temperature?
Sylvia: If you look at the net heat gains and losses from windows, south facing windows represent an overall heat gain, north-facing windows are a heat loss while east and west are neutral. Terrell Wong’s brilliant concept has allowed us to create the perfect solar (that is, south-facing) house that completely fits the naturally east facing slope. There are no north-facing windows. Our windows are also exceptionally good: Alphawin windows come from Germany with the Passiv Haus standard. You should talk to Terrell about the windows.
Composition of 18" thick walls
7. Can you talk a little bit about your business goals? Is your house the first in a series of rammed earth buildings?
Sylvia: Several years ago I retired from teaching to take on the project of building a sustainable house. I knew I wanted rammed earth but the highly technical nature of the process, from soil selection to forming systems and tamping techniques, seemed somewhat daunting. I also realized that my original concept of building one house as an example of what could be done was not as important as offering a genuine alternative in an attempt to change the built environment. To that end I incorporated aerecura sustainable builders and enlisted the help of an experienced rammed earth builder to construct the rammed earth garage as the first part of a steep learning curve leading toward the goal of a rammed earth industry in Ontario. Long before we put a shovel in the ground, and with no advertising effort on my part, I have received emails and phone calls from people interested in rammed earth. People are drawn to rammed earth for many reasons. Some, like myself, are attracted to the sustainability of rammed earth. Others, including many architects, are entranced by the natural beauty of the material as well as the creativity afforded in designing with rammed earth. Still others are seeking the health benefits of a building system with no toxic materials and no organic matter, thus nothing for moulds, insects or other pests to eat or burrow into. One family approached me after losing their house to fire; rammed earth is rated as non-combustible, another benefit of using only inorganic materials. My husband was entranced at the possibility of a fabulous music studio, using the superior acoustic properties of rammed earth. I have been contacted by people in Saskatchewan, Manitoba, Quebec and Nova Scotia, though aerecura’s initial business plan will keep us in southern Ontario. aerecura sustainable builders believes that rammed earth has the potential for widespread mainstream acceptance in both the residential and commercial realms.
For more information on rammed earth buildings, please contact Sylvia Cook at firstname.lastname@example.org