Building a rammed earth house was a logical decision for Sylvia Cook when she retired from teaching high school physics. Her goal was to build 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: dirt’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. 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.
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.
Rammed Earth 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.
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.
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 email@example.com, or, see her website.
This is amazing….had no idea until my sustainable resources class what the possibilities were! I also live in Ontario (Bancroft) and would love to build my home this way. Could you please send me extra resources to present to my builder?
Hi Crystal, you will have to contact Sylvia Cook, owner and primary builder at Aercura. You can reach her at firstname.lastname@example.org for more information.
So lovely & has truly inspired me to look further into Rammed Earth for my future eco friendly home, vs Straw bale (which is what I grew up in, & was built by my Father). I live north of Toronto and would love to move south to do this. Interested in creating a Rammed Earth sub division Sylvia? 😉 Enjoy your stunning home & Thank you for this article 🙂
We’d prefer to think of it as a “rammed earth eco-village”, but yes, definitely!
Regarding your usage of insulated rammed-earth, how significant was the thermal difference from uninsulated walls of equal thickness? Also, doesn’t the insulation effect the walls breathability?
Lastly, I dislike the reasoning that it’s okay to use polyiso since “we also felt optimistic that 500 years from now the technology will exist to recycle this”. Look at the environmental damage and financial costs that have resulted from the irresponsible practices of prior generations. It’s especially irresponsible for modern society since we presumably have a greater understanding of the implications, and its effect on successive generations.
Thanks for your comment, I’ll forward it to Sylvia, so she can respond.
I’m wondering why the owner hasn’t opted for a geothermal heat regulation system? It acts as both a heater/humidfier and an air conditioner/dehumidfier. My big old farm house uses one and it’s lovely, not as harsh as stove heat and costs very little to run. Just the well pump and the unit. I’m not sure of Ontario’s main source of energy but in Quebec, since it’s mostly hydroelectricity, it’s very green.
We had originally considered geothermal but even the early modelling showed energy use so low that we couldn’t justify the initial cost of the system or the ongoing energy to use it. We’ve now been living in the house for over a year with no air conditioning and very little heat and with the humidity controlled by the rammed earth. Soooo comfortable!
Before building with insulated rammed earth we did a lot of research into insulation possibilities using the criteria of sustainability, carbon footprint, health impact and recyclability. The negative aspects of polyiso were that it is a petroleum-based product and is not currently recyclable. However the positive aspects seem to us to outweigh these. Polyiso is one of the highest R-value per inch insulations currently available, which will dramatically reduce the energy consumption of the building for its centuries of use. Although it will degrade when exposed to UV radiation, that is not going to happen in the middle of a rammed earth wall, so its useful longevity may match the lifetime of the building. It doesn’t off-gas (though that too is not a problem inside a rammed earth wall) and is relatively benign to produce (our main concern here being worker safety.) We also felt optimistic that 500 years from now the technology will exist to recycle this and many other materials.
We also enjoy wood as a beautiful material when sustainably harvested and have incorporated it into our house as an alternative to drywall as well as using it for flooring and furnishing. However we do believe that using wood to create structural walls is not sustainable, using the definition that the planet must survive if everyone used the same method. The need for housing is clearly outstripping the 5% natural growth rate of forests, partly because we have been building stick-frame. A century ago houses could be built to last a hundred years or more because the wood was better quality. Besides the fact that “two-by” lumber used to measure a full 2”, a quick glance at the density of rings will tell you that old lumber was logged from old-growth timber which made it stronger and less vulnerable to insects and moulds. Those century homes also lasted because they are not airtight. Today’s houses are built with poor quality first-growth wood, which is then wrapped in plastic to achieve airtightness – a perfect recipe for mould growth, while the weakened, water-damaged wood becomes susceptible to insect depradation. Well before their third decade these houses need extensive renovation to deal with issues arising from the poor starting material, which is then hauled off to the landfill to be replaced by more of the same. Far better to achieve airtightness with a non-organic substance that is impervious to insects, mould or rot and has excellent thermal mass as an added benefit. In other words: rammed earth.
Interesting method. Kudos for thinking out of the box and trying something new (or an old method with a new twist).
I am sold except for the polyiso insulation. With that as part of the picture I wonder if it is any better than a well conceived and well built stick home with the wood coming from a sustainable forest and insulated with cellulose or some other biomass insulation.
I don’t have an issue with cutting down trees as long as we keep the forest and stay within the natural growth rate that nature offers (5% or so). If the house is built to last a hundred plus years then the wood becomes an effective carbon sink.
In any case we are in serious need of research and development into sustainable insulation materials and building methods.
I’d like to hear what others think.
Thanks for your comments regarding the use of polyiso insulation. I will pass your thoughts on to Sylvia Cook (builder and owner).
All the best,
What an interesting building method!
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Hi Tori, Yes the rammed earth house is really cool! Can’t wait to go back and see it when it’s completed.
Thanks for your comment.