Building with a Light Touch: My Off-Grid Straw Bale Home
This post was written by BC-based guest blogger Sharon Bamber (www.sharonbamber.com).
I live in a straw bale off-grid home. My husband Simon and I designed it and built it together from the ground up, with no special tools, no help from paid contractors (except for the final roofing) and no prior construction experience. It was a challenging, frustrating, exciting, demoralizing, enlightening, joyous and exhausting endeavour. I thoroughly recommend it!
I was introduced to natural building 20 years ago when I lived in Cornwall, UK, and learned about the traditional cob buildings. Cob is a traditional building technique using hand-formed lumps of clay earth mixed with sand and straw which is laid wet. In England, there are tens of thousands of comfortable cob homes, many of which have been continuously inhabited for over 500 years. Building in this manner made sense to me as this ancient technology is aesthetically beautiful and doesn’t contribute to environmental degradation, dwindling natural resources or chemical contamination.
When I came to Canada, I wasn’t sure if cob would provide the necessary insulation for the winter months. I still wanted that beautiful, unique, hand-built home that I’d dreamed of for so long, but didn’t want to hurt the environment in the process. Conventional building materials are non-renewable, difficult and intimidating for novices to work with and the environmental cost is high. I needed an alternative solution.
I asked myself a number of questions:
Where do the materials come from, are they sustainable and how much damage is done to the land when they are extracted?
The straw: I was able to source straw bales from a farm 148 kilometres away – further than I would have liked, but much closer than those conventional materials! The nearest oriented strand board (OSB) manufacturing plant is 650 kilometres away and the nearest fibreglass insulation manufacturing plant is 830 kilometres away.
In comparison with other building materials, timber/lumber seems like a sustainable material, but it takes a long time to grow compared to straw. Straw is a renewable material, taking just one season before it is harvested.
The earth plaster: The soil that we were going to extract as we dug the foundations contained enough clay to make a good plaster. So one of the major plaster ingredients was there on site. Using the soil extracted for the foundation as the basis of our plaster was much less damaging to the land than using cement or lime plaster and we minimised the physical footprint of our house as best we could. The other ingredients were chopped straw (sustainable), fresh horse manure (sustainable) and fresh cow manure (sustainable), both of which we collected daily from our neighbour’s horses and cows, and sand (not sustainable). The sand came from a local quarry 26 kilometres away. All very local!
What is the embodied energy of the materials?
Embodied energy is a common measure used in comparing the environmental impact of different materials, products or services. In this case, it is the energy consumed by all of the processes associated with the production of a building, from the mining and processing of natural resources to manufacturing, transport and product delivery.
Straw bale construction has extremely low measures of embodied energy when compared with conventional building materials.
What are the costs of heating and cooling the completed house?
Our house is extremely cool during the summer and very warm in the winter. Straw, when encased in earth plaster has a very high R-value. Other buildings can achieve the same R-value, but only by using more expensive materials and a more material-extensive system. It has been estimated that straw bale buildings are on average 20% more efficient than standard stick-built construction.
What happens to the building materials eventually, when the home is no longer needed?
At the end of its life, when the building is no longer needed, the walls can just compost into the ground. The walls and plaster are 100% biodegradable when the time comes. As an interesting side note, during the whole of the construction we only had to take two standard-sized black garbage bags to the dump. None of that came from the wall construction.
I love that I know that the materials are natural, that I know where they come from and how they are made, that there are no glues, chemicals, toxins or off-gassing. I love that I collected, sieved and mixed the plaster with my own hands. I love that I built every inch of the house and that I felt safe and comfortable doing it. I adore the really thick, solid walls with their gentle undulations, soft curves, rounded edges and deep window seats at each window. Those characteristics add a special warm, welcoming feeling that is impossible to describe until you experience it for yourself.
My home is powered by solar and has a composting toilet (a rather nice porcelain toilet with the nasty “working box” hidden away), and I have plans for a greywater system now that this is allowed under BC wastewater regulations. It is by no means the perfect environmentally friendly house. Except for the walls themselves, there were areas where we had to compromise because of budget, and I really hope that alternative sustainable green products eventually become more affordable and mainstream. It is however, the best that we could possibly do and we love it.