A Look Inside the Strawbale Walls of this Off-grid Home
Anke and Roberto are proud of their new home in Scotch Village, Nova Scotia, which was built on a breathtaking piece of land a short distance from the city of Halifax. They've also planted fruit trees, grains, and a large vegetable garden to supply their catering business, Conscious Catering. They used timber frame construction with straw bale wall insulation and powered it with off-grid solar power.
The home was designed by Michael Barton with a great deal of input from Robbie and Anke. Michael tailored their building systems to ensure adherence to local building codes.
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Michael is particularly proud that they got the first approved septic system in Nova Scotia smaller than 1000 L/day. They could do so by showing that using a composting toilet drastically reduces the need for a septic field.
The primary heat source for the building is the sun, so they oriented the house for maximum solar exposure. South-facing windows allow sunlight to enter in winter to provide heat. A concrete floor provides thermal mass to store heat and reduce temperature swings. They have a wood stove/oven for a secondary heating system that provides cooking and pre-heated domestic hot water. The firewood can be harvested from their property. About their home's thermal performance, Robbie says:
"If we go away on a sunny weekend in winter, of course, the wood stove is off, but still, we will typically come home to a +20°C house. We once went away for ten days in February and still returned to a +12°C house! This house is designed, so it will not freeze."
How about that? A house so well insulated that you don't need to worry about freezing pipes! A major bonus in a cold winter climate.
The rough-cut lumber for the house was sourced from a local sawmill, and some beautiful posts were sourced on the building site. To insulate their home, they used 18-inch thick straw bales from a neighboring farm. The straw alone provides an insulation value between R-25 and R-40.
Because straw bales are not a standardized building product, they needed Michael, their engineer, to prove that this thickness of straw satisfies building code requirements. On Michael's recommendation, they also took extra care to air seal around joints with acoustical sealant and tar paper to stop any drafts. Straw bales settle for the first few weeks, so they delayed interior finishing until after settling.
Strawbale walls give a comforting feeling of shelter because they are so thick. This makes the window sills spacious and the window wells very deep. To allow sunlight in through the deep window wells, they rounded the corners.
The walls are finished with natural clay plaster, which provides a naturally beautiful surface and helps to regulate humidity in the home. In dark or high traffic areas, the third and final coat contained lime, making the walls brighter and more durable. The clay was as locally sourced as it could be; in fact, it was dug from the ground near the house! The resulting pond now provides irrigation for their garden.
To insulate the pantry walls for excellent temperature food storage, they used a building technique called 'straw-clay slip.' This involves dressing straw with clay and packing it tightly between the wall studs. The clay acts as a binding agent to apply the clay plaster finish directly to the straw-clay slip. This technique was also used for the interior bedroom walls to help with soundproofing.
The closest utility power line is about 500 meters away. Instead of having a power line brought in (~$12,000), they got an off-grid solar photovoltaic system (~$14,000), designed and installed by Solar Global Solutions. To store the electricity, Robbie went online and found 16 used but perfectly operational deep-cycle gel-cell batteries. Their PV system supplies power for LED lighting, an Energy Star clothes washer, an electric hot water tank, two fridges, and numerous kitchen appliances. For little more than the cost of installing a power line, they have the electricity they want, with no power bills to pay.
Anke and Roberto have built a beautiful little paradise, celebrating the relationship between people, the earth, and the sun.
Details
- Built-in 2015-2017
- Square footage: 2000 sq. ft.
- Bedrooms: 2 (plus a roomy third-floor loft)
- Solar PV system: 4 kW off-grid
Why We Love it
- Passive solar heating
- Use of locally sourced building products
- Strawbale insulation
- Natural clay plaster wall finish
- Off-grid solar photovoltaic power
Article by:
Dane George
Dane George holds a Bachelor of Civil Engineering and a Masters of Applied Science in Mechanical Engineering from Dalhousie University. He has three years of experience working with residential contractors with a focus on energy efficient renovations, and has worked with the Clean Foundation as a Certified Energy Advisor conducting energy audits of homes. Most recently, his graduate research involved analyzing electricity consumption patterns. Dane has also prepared and delivered workshops on home energy sustainability, and is currently teaching Renewable Energy and Energy Efficiency at Saint Mary’s University in Halifax.