Posts Tagged ‘embodied energy’

An Interview with Sylvia Cook, Rammed Earth Builder

October 28th, 2010

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?

The lines represent different layers of earth

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

Ontario’s First Rammed Earth House

October 26th, 2010

Rammed Earth House -- Walls finished

When Sylvia Cook retired from being a high school physics teacher, she had the goal of building the most sustainable house possible. After a  lot of very thorough research, Sylvia determined that the best  material to build a house with was dirt. Think about it: it’s local, there’s plenty of it, it has a low embodied energy, it has a significant thermal mass, and is extremely durable. It was these last two criteria that sealed the deal sustainability for Sylvia.  When all is said and done, Sylvia estimates that her house will last, at a minimum, for about 500 hundred years. That’s not a typo. Five hundred years is a far cry from the minimum standard Ontario’s current building code demands which, if built to minimum specifications, is only about 30 years. So I applaud Sylvia’s vision and far-sightedness to undertake the building of a home that will outlast her great, great, great grandchildren, and hope that the Policy Developers-That-Be will consider upgrading the building code so that homes are built to last even half that long.

But I digress. I confess that when I imagined a rammed earth home, I imagined something out of the wilds of northern England or Scotland, sitting on a desolate wind-blown moor amongst the heather….but as it turns out I was way off. Way, way off. Instead, this rammed earth home has a more “adobe,” southwestern feel to it, but that could also be because Sylvia tinted the mixture with natural terracotta pigment to give it a warmer tone than its natural cool gray concrete appearance.

The basic building block for a rammed earth home: dirt.

Rammed earth walls consist of a mixture of dirt and sand with about 5% concrete mixed in. I asked if the dirt was off the property, but Sylvia said that the stones in the dirt on her property were too big to settle properly and would affect the structure of the hardened material. So, instead, she located a gravel pit about 5 km down the road from her property that has provided the dirt for her house.

Design: Sylvia worked closely with Terrell Wong, environmental architect, on the project. As this was Terrell’s first rammed earth home design, she mentioned that the design really came together when the two of them brainstormed. It was critical that Terrell knew what the material could do in order for her to design the most energy efficient home possible.  The house consists of three “blocks” with rammed earth walls built on the inside of the home as well as for the exterior walls. The walls, which are 18″ thick provide a significant amount of thermal mass. Thermal mass allows for a more consistent temperature throughout the house regardless of the season. The walls have an R value in total of about R50. Because of this design, Sylvia is convinced that she will need only a heat source of a small wood stove and an ERV (energy recovery ventilator) for the entire house. She must have seen the look of skepticism on my face because she said that Terrell had incorporated some baseboard heaters into the design “just in case.” I’m cheering for her.

SE facing windows. Future music room (bottom), Living Room (above)

To help out the thermal mass walls, the design calls for some significant windows on the south east side of the house which allow for light and passive solar heating in the winter. Terrell made sure the home was oriented so that the sun was captured through the south-east facing windows from October through April only, thereby avoiding direct sunlight during the hottest months.  There will be clerestory windows above the second floor, with a mezzanine that looks down to the main entry and living room. These windows will open to allow any rising heat in the summer to escape easily. All the windows were ordered from Germany and meet Passive House standards, meaning that they are the most thermally efficient windows on the market today.

In fact, with respect to the orientation of the house, Terrell had this to say:

The building faces perfectly on the cardinal compass points NSEW.  The views are all to the east and the sun is to the south.  What to do… So it’s 3 volumes (2 shoe boxes)set apart and  splayed 8 degrees from one another and, they are also shifted so that there are south facing windows in every main room.  These windows occur either in the jogs created by the shift of above in the clearstory mezzanine and those south facing windows project light and heat on the main 24’ high interior rammed earth wall.  The windows facing east are for views and will require some external shading (yet to be determined) so that the building does not overheat.  What we suspect though is that the rammed earth will absorb much of the excess and retain it when the reverse is true.

Construction method: Dirt, sand and concrete are mixed together in specific proportions to create a substance that will last when compacted, as mentioned, for at least 500 years. The mixture is shoveled in to a mold which is set up in 4′ x 8′ x 0.5′ sheets. About 8″ in height of dirt is added to the mold and then tamped down with a hydraulic tamper. The process is repeated until the top of the mold is reached. It’s topped off and leveled, then the next panel is constructed. Construction consists of a 6” exterior rammed earth, 6” polyiso insulation and 6” interior rammed earth, giving the entire construction an over all R value of around R-50. The roof consists of Thermapan SIPs panels, with an R-value of 40 plus the metal roofing material.

The home’s walls are now finished, but the first floor still needs to be constructed, then the windows, doors and roof. I can’t wait to see this house when it’s fully put together.

Sylvia’s home is the first of many rammed earth structures to be built by her company, Aerecura. For more information on rammed earth buildings, please contact Sylvia Cook at, or, see her website.

Natural waves in the walls due to the layering of the dirt mixture

Close up of the layered dirt.

Sandwich of rammed earth, insulation, rammed earth

Building Green taking into account “Embodied Energy”

April 22nd, 2010

There are many definitions of “green building.” For some it’s all about indoor air quality and making sure your home is not emitting fumes that are potentially hazardous to your family’s health. For others it’s about reusing what you have, renovating and making your new-old home tighter and more energy efficient. Finally there are those of us (myself included) who fall into the “embodied energy” category.

Today I watched a fantastic six minute video by Catherine Mohr who was invited to speak at TED 2010. If you can spare six minutes I encourage you to watch this funny and enlightening video on the trade-offs she and her husband consider while trying to build a green house. They have focused on trying to build using materials with the least amount of “embodied energy.”  This is the link to her talk:

If you’re not familiar with the term, “embodied energy” refers to the amount of energy it takes to make something and therefore, that energy is considered “stored” in the finished product. For instance, according to Catherine, it takes approximately 300 Megawatt hours of embodied energy to produce the average single family home. She set out to build her own home using significantly less energy, while building a home that will in the future also use significantly less energy than the average single family home.

If we can bring each product or activity we buy or do down to the amount of energy it consumes we can make more informed decisions about which product is best. So, that being said, Catherine’s decisions led her to choose wood-framed windows over aluminum, cotton and strawbale insulations over sprayfoam. Her house will still be as energy efficient as if she’d chosen the alternatives, but she used materials that take less energy to produce and ship to her house.

Catherine has been documenting her journey on the path to building green at It’s an excellent blog, full of all of her decisions and the thought process she went through to choose each material. She also lists her trades, services, and materials suppliers (she lives in Silicon Valley).

I have to admit that after watching her TED talk, I wondered how she had done her embodied energy calculations, there are, after all, a lot of variables involved when calculating the embodied energy of a product and much depends on what type of energy is used where the product is produced (coal vs. natural gas vs. hydro vs. nuclear). Fortunately, after reading through her posts I came across the one that explains how she did her EE calculations, as well as attaching her Excel spreadsheet with the calculations. She also did another spreadsheet showing how her much energy her lifestyle consumes.

If you have a chance, look through her blog. It’s an interesting read, as well as a great resource for trades and services in the Silicon Valley area, and green products that are for the large part available across North America.

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