What is an Autonomous House?
Do you feel that you're lacking a connection with your environment?
Would you like to live in a house where you are in control of the services?
This article is a case study of a couple who created an autonomous house. We find out why they did it and how different it is to live this way.
Autonomous Means Possessing a Large Degree of Self-Governance
Mike Coe and Lizzie Stoodley built themselves an autonomous house in Cropthorne, Worcestershire. Although being autonomous might imply no connection to the outside world, in their case this is not strictly true because they are linked to the grid (albeit to export more electricity than they use!).
If they were completely self-sufficient and off-grid in all respects they would have an autarkic house, but autonomous is a better description of their home. They have no gas supply, they derive their water from harvested rain and they deal with their own human waste.
Architects Brenda and Robert Vale Inspired Them
The initial seed of an idea came in the 1990s, before they had any plans to build a house. Mike was an ITV News cameraman and he was sent to Southwell, Nottinghamshire, on an assignment to do a story on a new kind of house.
Mike describes his visit: “Nobody had the faintest idea what it was. Only when I got there did I realise that it was fascinating. We did an interview with Robert Vale and he showed us around and I thought this is a really interesting project.”
The feature was never shown on ITV because another story broke, but Mike's journey was not in vain. He had been inspired.
Many years later Mike and Lizzie were considering a long-term plan to leave London and live somewhere less hectic, when they returned to the idea of an autonomous house.
Increasingly concerned about what the human race was doing to the environment and with a strong desire to take action somehow, the ideas came together in their ultra low energy house. It would be based on the house at Southwell but would try to take everything to the next level, with improved materials and greater experience, etc. As this was a once-in-a-lifetime opportunity they wanted to do this properly and take the ideas as far as was sensible.
In 2006 Mike and Lizzie bought their plot of land
Passivhaus Offered the Best Approach
Mike was convinced that the basic configuration of Brenda and Robert Vale's house was correct. It had a very high thermal mass – based on a concrete core – surrounded by a huge amount of insulation, built as airtight as possible with super high performance windows. Although Brenda and Robert Vale's house had a small wood stove, Mike and Lizzie believed they could create a house that didn't need a heating system and just relied on incidental heat (body warmth, cooking, heat from appliances and so on).
While the house was designed and constructed using Passivhaus principles it hasn't been certified, although this could (easily) be done at a later date. In fact the primary energy requirement of their house is between 3 – 4 kWh per m2 per year, which is four to five times better than the Passivhaus requirement.
An Inverted Layout Takes Advantage of the Fact That Heat Rises
In terms of design the house is upside-down. So the living area is upstairs, taking advantage of the fact that heat rises. In a house with no heating it makes sense to live where it's warmer during the winter. Also, during very hot summer weather, the bedrooms, being downstairs, stay cool and are therefore more comfortable.
If Mike ever builds another house he would definitely do it the same way again.
You Must be Adaptable to Live Like This
Living in an autonomous house requires more thought than a conventional dwelling. However, it's good thought! The user needs to understand how the building works in order to get the most out of it. For example, controlling the temperature is about considering what to do with the heat. During the summer, Mike and Lizzie warm up the core of the house to a comfortable temperature. They make sure that they close windows and doors when they need to store up heat for the winter. Also, in autumn and winter the mechanical ventilation system is in heat reclaim mode whereas during the summer they don’t reclaim any heat.
Mike says: “You’re much more in touch with the seasons and the outdoor environment and you modify your behaviour accordingly. You have to be prepared in the depths of winter to wear a jumper.”
Responsibility for Resources is Back with You
In today's world, so long as we have money we know (or perceive) we can have the resources. This not only shifts the responsibility onto somebody else – our service providers – but it distances us from what we're actually doing to the environment. To live in an autonomous house it is necessary to be more in touch with the environment which Mike sees as a very good thing.
Mike and Lizzie have 17 tonnes of water storage in their basement, but they still need to modify their behaviour if they are anticipating a prolonged period of dry weather. This might mean not cleaning the car or taking showers less often.
“We derive all of our water supply from water that falls on the roof. We store it, we purify it, we drink it, we wash in it and we wash our clothes in it. And it ends up back in a soakaway in the garden.”
The same amount of water enters the site as would have done had the house never been built. All they do is borrow it.
Mains Electricity Makes Sense at the Moment
Mike explains that it’s not environmentally and economically sensible to go off-grid if you have access to a mains electricity supply. This is because storing electricity is not straightforward. For example they could use banks of lithium or nickel metal hydride accumulators but they contain a lot of chemicals. Plus, with this set-up there might still be trouble supplying the house at periods of peak demand.
So, at the current time there is little financial or environmental advantage. Instead they effectively use the grid as a battery!
Most of the electricity generated by their 2.3kW ground-mounted photovoltaic array gets exported because the energy demands of the house are so low. At night time they consume power from the grid, but it's a small amount. The total electricity bill for the house is in the region of £350 per year and as the payment they receive from the photovoltaic array is about £900, they make about £500 income.
Mains Water and Sewage Systems are Not Efficient
There's a lot of energy involved in providing houses with clean water and removing the sewage.
While doing his research Mike discovered that 30 – 40% of the water consumed in a normal house is used for flushing the toilets. In most cases it is also clean drinking water, which is of course very wasteful.
Human waste is actually quite a useful substance because it has similar properties to a fertiliser. Mike sums it up well: “What we normally do is we mix useful human waste with useful clean drinking water and we produce a problem substance called sewage, which we then have to pump several miles using energy and process it in a local sewage treatment plant.”
The composting toilet being installed
Composting Toilets Made Sense
With heating and lighting, adjusting lifestyle can often result in huge energy savings. However, when it's comes to human waste you can't really reduce the number of times you need to go to the loo! That's why Mike and Lizzie were keen to bring all those services in house and provide them without using any external energy.
Mike explains how it works: “Every two months, with two of us living here, we have to maintain the chamber which means we have to drain out all the liquid compost and we have to take out the solid compost [that's mixed with wood shavings], but by the time you come to do that it genuinely isn’t unpleasant.”
This compost then goes on the garden and this also means that they don’t need to buy any fertilisers.
In the Event of Fuel Shortages, They Would be Well Placed
Building an ultra low energy house is in a sense adding an element of autonomy, because you’re reducing your reliance on external fuel supplies. Reflecting on how their life would alter in times of scarcity or blackouts, Mike says they would stay warm because there's no heating system to go off! There would be no issues with their water either. Electricity would be fine during the day but they might be inconvenienced with a prolonged power cut.
Running an Autonomous House is Rewarding
Mike and Lizzie have never looked back since embracing this way of living. Mike concludes: “The main thing is you have to think and you have to want to be responsible for your actions. That isn’t a hardship – it’s quite rewarding. I think it’s a good way to live.”