Donnachadh McCarthy refurbished his nineteenth century London home so efficiently that he now sells electricity back to the British national grid. How did he do it?
 | Donnachadh McCarthy, Carbon Negative Homeowner"There is an extraordinary educational value in going for renewables first because it teaches you the cost of electricity production" (Photo: Donnachadh McCarthy) |
You are famous as London’s first carbon negative homeowner. How green is your house?
I’ve been carbon negative for three years. My house exports around 20 percent more electricity than it consumes. This year I sent a bill to London Electricity for about 60 pounds (100 dollars). Next year I’m hoping for 300 pounds, when a new premium feed-in tariff for renewable energy is introduced.
My water consumption is 22 liters per day whereas the London average is 160 liters per day. Non-recycled waste is about half a wheelie bin a year, and my gas bill last year was about 12 pounds.
So how have you turned a house built in the 1840s into such an energy efficient building?
The house has got five renewable technologies: solar electric panels, solar hot water panels, rainwater harvesting system, a domestic wind turbine, and a wood-burning stove.
People say you must concentrate on energy efficiency first, insulation and all that. I broke that rule. But there is an extraordinary educational value in going for renewables first because it teaches you the cost of electricity production.
When I first looked into it in the mid-1990s, battery and storage systems were big problems, but that was solved in the late 1990’s when it became possible to use the national grid as a battery. In the summer I sell the grid electricity, in the winter I buy. Over the year I am a net exporter.
Which technology is the biggest energy saver?
The most successful is the wood burner. It burns the smoke twice like a catalytic converter, which means it is licensed for urban smoke-free zones where you can’t burn coal or wood in an open fire.
In terms of reduction of carbon emissions, they up to 70 percent of a domestic home’s carbon footprint is space heating, and this burner has provided all my space heating for three years.
My house is open plan downstairs and has two bedrooms upstairs. The wood burner is in the middle of the downstairs area, with an eco-fan (powered by the heat) on top that distributes the heat. The chimney of the burner goes through the main bedroom upstairs and heats the rooms up there.
The ultimate solution would be to have the wood burner integrated with the solar panel heating and radiators to heat upstairs. But that would have meant ripping the house apart and I wasn’t prepared to do that.
Where do you get the wood?
This is an area of Victorian housing and houses are always being refurbished. There is always fresh, untreated wood being thrown away. I started asking local people for untreated spare wood and now I often open my front door and there is wood waiting on my doorstep
I haven’t spent a penny on wood for three years. I reckon the amount of waste wood in my neighborhood could power around 10 percent of the houses.
How successful are the other technologies? Would you do anything differently?
The solar hot water provides water for about 60 percent of the year. I have an electric immersion heater as backup. The rain harvester on the roof provides about 80 percent of the water for my toilet.
I’ve got a useless wind turbine. It just hasn’t produced what I was hoping for. One problem is that over two or three minutes the wind will fluctuate enormously, but it takes a few minutes of constant wind for the turbine’s inverter to start operating.
How much did this retrofit cost? Did you get any government help?
Over 12 years I think I’ve spent about 20,000 pounds (33,000 dollars). I have paid about 3000 pounds in VAT (value added tax) on installations and got 450 pounds in grants so Gordon Brown has penalized me more than rewarded me.
However, government is getting better. VAT on energy efficiency products has come down from 17.5 percent to five percent which makes a significant difference.
Have you made your money back and added value to the house?
Some estate agents have said that a green retrofit could add five percent to the selling value of the property. If this house is worth around a quarter of a million pounds, then I’ve made back about 12,500 pounds. Over 12 years I’ve saved about 7,200 pounds on utilities bills, so I’ve about broken even.
And from next year I should be earning around 300 pounds a year when a new electricity tariff is introduced for home generated power. Add to that the likely increases in fuel prices over the next 20 years and it will more than pay back the investment.
Do you have to live in a house for a long time to retrofit like this?
Yes, absolutely if you want to benefit financially from the investment. Obviously we want everyone to do it now because of the urgency of the climate crisis but to expect someone to pay for this themselves when they are going be in a house for a couple of years is a bit silly . What is needed is a major government-funded drive to retro-fit all existing houses.
What’s the biggest lesson from your experience?
The main thing is lifestyle. One reason why I’ve been so successful is that I measure everything. It is good practice, so I’ve helped set up a website www.nationalcarbonfootprintday.org where people can register for free to be reminded to measure their footprint every year on National Carbon Footprint Day on October 2.
Take lighting, for example. The bulbs in my house use around 100 watts in total. If I was using conventional bulbs, that would be about 1180 watts. Most of them are LEDs. Traditional lighting floods every room with the same light, but LEDs offer sharp or diffused light depending on whether you need it for reading or just going upstairs.
How do you feel having achieved all this?
Anyone can have a BMW outside their front door but to have the first carbon negative house in London is something really special. I am passionate about tackling this crisis, millions of peoples’ lives and homes are at risk. I want to do something.
One of the reasons the environmental movement has not been successful to date is because politicians, journalists, and campaigners have not been doing it themselves. If the public picks up that we are not doing it, then they will feel intuitively that it is not that urgent. There is no credibility. It is crucial to me when I stand in front of audiences urging urgent action that I have literally put my own house in order.
Donnachadh McCarthy is a member of the Old Home SuperHome network run by U.K. charity the Sustainable Energy Academy. http://www.sustainable-energyacademy.org.uk/
editor: James Tulloch
publishing date: September 14, 2009
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Interesting stuff
It would be excellent to see governments around the world force new home builders to implement some of these simple technologies into all new homes. Personaly, I look forward to the...