We have one of the most beautiful food co-ops in Australia! It lives in a purpose-built, pasive-solar, straw and earth building.
The majority of the timber in the building is macrocarpa (Cypress macrocarpa), which is a tree native to California that was planted widely by early farmers in Tasmania to act as windbreaks. Many of these old trees are now nearing the end of their natural life-spans. This timber was sourced from an old farm tree and milled by local timber-worker Forrest Whitten. Macrocarpa is a strong, light and highly durable timber.
The timber on the ceiling is recycled and was donated by Lance Wilson from a house demolition. The shelving and drawers are made from Australian native plantation plywood, and the counter is constructed from a locally-milled, wind-felled blue gum and recycled timber from the tip-shop.
Properly sourced timber from small-scale operations can be a sustainable building option, as it is renewable and captures carbon. Our timber does not come from unsustainabley-harvested native forests or large-scale monoculture plantations, here or overseas, and has no toxins like treated pine. All the waste from the building process has been used landscaping the site or they have been burned to cook pizzas in the oven.
The back of the building is constructed of straw bales coated in an earth render. Straw bales have been used as a building material for centuries. Straw bale walls are very resistant to fire, vermin and decay and straw bale houses can last up to 100 years, providing the straw is reasonably well protected and it doesn’t get wet. Straw bales also have excellent insulation properties as they contain many air spaces which trap warm air.
Straw is a renewable material and its associated greenhouse gas emissions are 50 times less than concrete. Straw can be a waste product on farms as it cannot be used for feed like hay. Its primary input is solar, although there is some environmental impact from growing and harvesting it on a farm.
There was no waste from using straw as the left over was used in the garden as mulch. We also liked using straw bales for Source as the building process was very hands-on and well suited to workshops and volunteer-based projects.
The earth render that was used on the Source building contains no concrete, which is a high embodied energy project. The render was made from earth from the site and hay which was mixed with a fermented brew made from apple, barley and cabbage juice (although almost any fruit and vegetables can be used). This fermentation process changed the render on a cellular level, increasing its strength, durability and water resistance. It also gave the building an interesting (but not bad) smell as it was being constructed! As well as having very low embodied energy, earth renders are superior to concrete renders as they breathe, just like a gore-tex raincoat breathes while a plastic raincoat does not. Any humidity from inside the building is released without it sweating or condensing on the inside of the straw bales. The final coat of render that gives the building its colour contains three parts sand, one part clay and one part milk. The protein in milk helps bind the render, and we used three different clays sourced from dams and road cuttings in Lune River, Geeveston and Lorinna to give us three different colours. There is a deep red clay on the outside, and lighter golden yellow and some white clay on the inside to reflect more light.
CLAY LIGHT STRAW WALLS:
The clay light straw technique was used to infill the walls at the front of the building. It was used instead of plasterboard and contains less embodied energy. It also gives insulation to the wall cavity. The technique involves dipping loose straw in a clay and water mix, then lightly compacting it in a timber formwork to fill wall cavities. Volunteers were able to participate in this very dirty process. The mud and straw dries in this position, the timber formwork is removed, and earth render is applied on top of this surface. Earth render and a clay top coat was applied on the internal side of this wall, and macrocarpa timber on the outside.
A concrete slab has provided the foundations and the floor of the Source building. Concrete does have a high embodied energy and associated greenhouse gas emissions due to cement production and the mining of raw materials. However it is often required by building engineers as a stable and long-lasting foundation. A positive aspect is that concrete slabs have a high thermal mass, which is the potential of a material to store and re-release heat. This helps regulate indoor temperatures by absorbing heat when it is warm and radiating heat when it is cold, creating a heating or cooling effect. Concrete is also very durable and its permanency can offset some of its high embodied energy. It is also possible to obtain more sustainable versions of concrete, that use recycled crushed concrete or industrial by products instead of natural sand or crushed rocks. Earth floors are another possible option, which also perform a thermal mass function.
THE FLOOR TREATMENT:
Council regulations required that the floor surface be “smooth and easily cleanable”. Many widely available techniques for polishing and coating a concrete floor use toxic chemicals and are quite expensive. We used an experimental treatment with natural beeswax, linseed oil and a citrus solvent. The linseed oil was diluted with the solvent at an approximate ratio or 1:1. This was liberally slopped on the floor with rags, then the areas where the oil had pooled were mopped up after half an hour. We then waited a week for the oil to soak in a repeated this process and waited another week. The patches with excess oil were cleaned up with citrus solvent and a rag. Then the floor had to be well cleaned of dust and dirt, and beeswax shavings were diluted in the citrus solvent until they formed a runny paste (with a consistent texture of jam without lumps). This was splattered on the floor and buffed, using about 1 tablespoon per 2 metres square of floor. This treatment was also a lot cheaper than any other options, looks good and performs well.
WATERPROOFING AROUND THE SINK:
Council regulations require that the walls around sinks are treated with a waterproofing agent. Many of these are toxic or expensive. We have used an ancient Japanese technique that involves adhering rice paper to the walls with unripe persimmon juice. Volunteers participated in this process, crushing green persimmons and dabbing on the juice with a piece of cloth. The tannin in the persimmon juice helps to waterproof, insect proof and strengthen the paper, and also gives it antimicrobial properties.
We are fortunate to be located on a north facing slope, which gives us the maximum amount of sunlight in winter. The windows are located on the north facing side with few windows on the south side. All the windows are doubled glazed, which is an expensive initial cost, but is a big contribution to the heat-retaining properties of the building. There are also insulation bats in the ceiling to stop the heat escaping. The concrete floor provides thermal mass, which absorbs heat when it is warm and radiates heat when it is cool. It has not been below 15 degrees in the Source shop this winter. The eaves on the Source building do not perform a solar passive function, they are purely to protect the straw bales from the weather. In hotter climates, eaves are a useful feature of solar-passive houses as they block the midday summer sun, but let morning and winter sun in.
WINDOWS AND DOOR-FRAMES:
Source is a volunteer-run project, and many people were involved in making decisions and organising the construction of the building. Looking back we would have done some things differently. One mistake was the use of PVC window and door frames. The toxic chemicals associated with the production, use and disposal of PVC threaten the environment and human health. These chemicals include dioxins, which are a known carcinogen and hormone disrupter, persist for many years and, accumulate in the fatty tissue of living organisms. If we had to make the choice again we would use wooden window and door frames.
See: archive.greenpeace.org/~toxics/reports/whatswrong.pdffor more information on PVC.
At Source we have a water tank to harvest rainwater off the roof for use on the community garden. This reduces our demand on mains water as well as the amount of storm water run-off into rivers and oceans. It is also better for the plants as it has not been treated with any chemicals to make it 'clean'. Technically we are not supposed to drink our rainwater, so the shop is also plumbed to the town water supply. However, rainwater can be made much safer for drinking if the first flush of water off the roof runs to waste, as this will be the most contaminated with animal and bird faeces and dust and particulates from urban pollution. (We have not installed this system at Source yet). It is also important to cover rainwater tanks to prevent mosquito breeding and to reduce evaporation losses, contamination and algal growth.
Grey water is any water that has been in household usage, except for water used in the toilet. This water can comprise 50-80% of residential waste water that is currently pumped to a chemical treatment plant and discharged into the ocean.
At Source we have a simple grease trap and grey water absorption trench. The water from the sink first drains into a grease trap, where solids sink to the bottom of the pit, which is emptied every fortnight. Water flows out of an outlet pipe about half way up the pit. It then flows into an arched pipe embedded in a 6m by 1m trench. The pipe is designed to distribute the water evenly across the trench. The size of the trench is designed to cope with the estimated volume of water from the shop. Water filters through the soil and also evaporates off the surface of the soil. The upper, most biologically active region of the soil is very good at purifying grey water and protecting the quality of natural surface and ground waters.
Originally we wanted to treat Source's grey water so it was suitable for irrigating the orchard and vegetable garden. However council regulations required us to have a large and expensive filtration system, which was beyond our means. We were able to come up with a compromise, which allows the waste water to be distributed on site, but does not allow us to use the water for irrigation.
There are many different ways for treating and using grey water that can be implemented at home. Many people simply divert the outlet from their washing machine straight onto the garden, or put a bucket under the shower. You do have to be careful that cleaning products are non-toxic, have low salt and phosphate levels and have neutral pH. Grey water can have pathogens so it is best not to store it for more than 24 hours, and make sure it doesn't pool on the surface of the ground. The safest way to distribute grey water is with a subsurface drip. There are a variety of treatment systems that can be installed in people's homes which include sand filtration and constructed wetlands, however these require more water than we use at Source to sustain.