Ebay Eco-Home 4, What is an Eco-Home?
I’ve been asked why this house is an ‘Eco-Home’. The term is much-abused and there’s a lot of commercial ‘greenwash’, companies proclaiming dubious green credentials to increase sales. ‘Carbon offset’ is an example (this is relevant, please bear with me). You can’t ‘offset’ burning fossil carbon (oil and coal) by planting trees! Oil and coal have been buried and removed from the carbon cycle for hundreds of millions of years. Digging them up and burning them returns them to the carbon cycle. It means more carbon being cycled between living green plants (which absorb it) and the atmosphere (which it returns to by decomposition or burning). You can’t offset mined carbon by rearranging the carbon that is already in the cycle at the surface (planting trees). The only way is to re-bury it so deep that decomposition can never return the gasses to the surface. Or to fuse it with some substance that will never decompose. Burning mined fossil fuels can never be offset by tree-planting.
This is relevant to Mark’s building because it’s heated by waste-wood from old pallets and the surrounding woodland. Burning wood is almost carbon-neutral if it doesn’t involve deforestation. Wood is already part of the cycle, burning it just returns it to the atmosphere, where it would return anyway by decomposition, and where it can be taken up again by other green plants. It’s not completely carbon-neutral if you use fossil fuels to power tools to cut and transport it.
Mark’s place also uses mainly reclaimed or recycled materials. This is significant as approx 1/3 of the total energy used by a dwelling is typically consumed as embodied energy, used in the construction materials themselves long before anyone turns the heating on!
There are massive amounts of insulation being used in Mark’s building. Without commissioning a thermal engineer’s report I’m not sure it would pass current regulations however. With today’s more stringent thermal regulations, new homes would have been ‘eco-homes’ twenty years ago. The main area of doubt is the covered atrium. Such a large area of glass will be a wonderful light feature in the summer but cause massive heat-loss in the winter. Which brings me to…
The biggest non-eco factor is the shear size of the building, but only if it remains fully inhabited throughout the year. Heating will require a lot of energy but it’s so large Mark and his friends will be able to retreat from the atrium and inhabit just a small portion in colder times or when fewer people are present.
Incidentally ground- and air-source heat-pumps are only green-tech if powered by electricity from renewable sources. If the power comes from fossil fuels they actually produce more CO2 than a conventionally efficient gas-condensing boiler. This is because most (average 70%) of the power produced by burning fossil fuels to produce electricity is wasted in the generation process (friction and lost heat) and transmission. The resistance of the cabling wastes electricity heating the high-tension cables, just like an electric radiator and they emit this as lost power to the environment.