Meet the

Meet our energy saving pioneers.

London, Camberwell, Coleman Road


House Summary

Owners: Donnachadh McCarthy
House Type: 1840’s Victorian terrace
Carbon Saving: 100%
Installed Measures:
  • Carbon neutral
  • Solar thermal panels (evacuated tubes)
  • Photovoltaic panels
  • Wind turbine on the roof connected to the grid
  • Wood-burning stove
  • Flueless gas fire 100% efficient
  • Embedded catalytic converter converts gas to heating
  • Low energy lighting
  • Rainwater harvesting
  • Personal Story:

    Following my own eco-refurbishment of my house I have set up an award winning eco-auditing consultancy.


    In 1992, during a trip to the Amazon, I spent time with the Amanye Indians and came back gutted about what we are doing to the planet and how we are destroying peoples lives with our own lifestyles. I decided I needed to do something about my own.

    I am saving energy in the home because I think we have a whole range of environmental crises that are out of control and if we don’t do something as rapidly as possible the planet will be in even worse trouble. Although I don’t see it as just saving energy, it is about reducing pollutants and saving resources, food and water.  I do it in my own home because I don’t believe I can actually tell people to do something unless I have done it myself: politics by example. To me this is what a Superhomer is.

  • Property:

    3 Acorns Retro Eco-house:
    1844 Victorian terrace two-bedroomed house, converted into London’s first retro carbon-negative home. It sells more green electricity to national grid than it imports fossil fuels. See examples of possible Green Deal investments including solar electric and hot water panels, wind-turbine, wood-burner, rain-harvester, triple-glazing, solid wall and under-floor insulation, range LED bulbs. Display on green-lifestyle. Owner is eco-author and business eco-auditor.

  • Measures:

    While it is essential to a low carbon home to use the home efficiently and ensure all the basics such as insulation and energy efficient appliances are in place, certain technologies can help.

    Eco-technologies used in the 3 Acorns Retro-Eco House:

    Solar Electric Panels
    The house was the first private home in London to export solar electricity from the roof to London Electricity in 1997.
    The 1.2 kW rated system was installed by Sundog Renewables. In 2006/7, the house exported about 20% more electricity to the national grid than it imported.
    Following EDF energy’s energetic lobbying of the UK government to promote a catastrophic new generation of nuclear power stations, he is switching to exporting his green electricity to Good Energy’s micro-generators scheme.
    The display on the right shows how much electricity the roof is producing, how much is being imported or exported and how much the house is consuming. In 1997 the system cost about £12,000. Solar electric systems today cost about the same but produce twice as much electricity.

    Solar Hot Water Panels and System
    The solar hot water system was installed 2 years ago and supplies about 70% of the household’s hot water needs. The vacuum tube heat exchanger system was installed by Southern Solar.

    In summer the system produces far more hot water than is needed and the temperature has to be regulated to prevent it from becoming too hot!

    The system cost about £4,200 but a £400 grant from the LowCarbonBuilding Programme and £500 from the local council brought the cost down.

    Catalytic Converter Flueless Gas Fire
    Unlike open coal-effect gas fires which are less than 20% efficient and traditional radiant gas-fires which are about 65% efficient, flueless gas fires are extraordinarily 100% efficient.

    Using an embedded catalytic converter, all of the gas is converted to heat, with water being the only by product. This means that they are only useful in houses which have central heating in the background or have a regularly used wood stove, as these dry out the resulting condensation.

    In my house, whilst very rarely used since the installation of the wood burner, it acts as a very handy back-up system in case I am ill and cannot use the wood burner or if in the house for a quick half hour before going out again and I need a burst of heat. They cost about £500 and I got mine from Burley’s.

    Rainwater Collection Systems
    The toilet in the bathroom and a designated tap are supplied by a simple gravity fed rain-harvester system, which sits on the flat roof immediately above the bathroom. It has supplied over 70% of the WC water needs since it was installed 9 years ago. The main legal requirement for such systems is that the rainwater cannot mix accidentally with mains-water and so special valves are required if you want the system to be backed up with the mains.

    The garden water needs are supplied from a tank that collects rain water from the lower roof run-off. It is now quite old but still does the job, with it’s own tap.

    Three Acorns Retro-Eco House was the first house in London to gain planning permission for a grid-attached building mounted domestic wind-turbine. It was installed in November 2005 but has not been a success to date.

    It produced a recorded 16kWh last year, which is about £1.60 off the electricity bill. There have been no noise complaints from neighbours, which is great, but there is currently a vibration problem internally in the house.

    StealthGen, the providers, continue to experiment with the product and the jury is out as to whether such small urban wind-turbines will make a worthwhile contribution in the future, even if some pessimists rule them out completely. It cost £2,800 installed.

    Last, but by no means least, 3 Acorns Retro-eco House has a wood burner in the open plan living room/dining room/ kitchen area. This is by far the greatest contributor to reducing the energy carbon footprint of the house. People often forget that electricity consumption on average is responsible for only 30% of the average house’s carbon footprint, whereas space and water heating account for the other 70%.

    I got mine from UK manufacturer Clearview Stoves. It cost about £800 plus £2,000 for installation and new chimney flue.


    Since 2003 the house has been a net exporter of electricity but in 2006/7 Donnachadh achieveD his dream of a not only a carbon neutral home but it actually become climate positive i.e. it is carbon negative exporting more green electricity to the national grid than it imports fossil fuels (gas).

    It has now been carbon-negative for three years.
    *(Average UK household carbon footprint = 6 tonnes (6,000 Kg))

    Water Consumption
    28 litres of mains-water per day.
    (London average mains water consumption = 160 litres per day)

    Non-recycled Waste Production
    Donnachadh ended up in 2006/7 being a net importer of waste!
    Domestic non-recycled waste: half a wheelie bin for entire year
    Building waste: 3 wheelie bins for year
    Imported Waste Wood for wood burner: 48 wheelie bins for year
    Net Waste IMPORTED !! : 44.5 wheelie bins

    Favourite Feature:

    The solar electric panels are a contender because once they’re installed you can forget about them. The wood burner has been the most effective in giving me the most pleasure but it is also the measure that requires the most on-going work and maintenance.

    I am most proud that the house was London’s first home to sell electricity to the national grid as well as being London’s first home to get planning permission for a wind-turbine. My home was also London’s first home to be carbon negative i.e. it sells more green energy to the national grid over the year than it imports fossil fuels.

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