From the outside, Sarah Harrison's three-bedroom home in north London looks like a typical red-brick Victorian semi. Step inside and, to the untrained eye, there is little evidence that it has been renovated using green energy technology.
"People are surprised that it looks and feels like a nice but normal Victorian house," says Harrison, who has achieved about 80 per cent energy efficiency savings through her green refurbishment. "They expect a modern look, and are surprised you can make it energy efficient without giving up the period aspects."
Most of all, though, people are surprised at how cheaply Harrison has managed to reach her carbon saving goals. When she bought the house in 2004 it required a total refit. "The roof was leaking and the heating was barely functioning. It was a freezing house with a lot of condensation. There wasn't a shower, the kitchen was on its last legs and it needed redecorating throughout."
In the end, the refurbishment to the highest of environment-friendly specifications cost about £15,000 more than the polluting alternatives. Much of the green technology installed has fallen in price in the intervening years.
Harrison was aware of the received wisdom that period homes are too costly and difficult to upgrade along ecological lines. "When I started to do this people who were interested in climate change said Victorian houses were an energy disaster and should be pulled down," she recalls. "I have always loved living in these houses and I wanted to find out whether it was possible, and then to say, 'We don't have to pull down these houses because it's cheaper in money and energy terms to make a Victorian house energy efficient'."
She has been proved right. As a result, her home is being used as an example for others who might want to do the same by a charitable organisation called the Sustainable Energy Academy (SEA), which works to reduce the carbon footprints of buildings. Harrison's home is one the SEA's 28 "SuperHomes", mostly built before 1919, which have already been visited by more than 36,000 people to see how they can do similar renovations.
The SEA's founder, John Doggart, who built Britain's first solar-powered house back in 1973, points out that renovating existing properties is a far more sensible than replacing them with energy-efficient new-builds. "If we had a carbon neutral policy for all new houses by 2050 we would make only a 1 per cent saving. This saves 20 per cent."
Last month, Doggart accepted from Prince Charles a sought-after Ashden Award, presented for leadership and achievement in the green energy field, along with a cheque for £30,000 to carry on the good work. Any major renovations are timely and costly, but the biggest single thing you can do to improve the energy efficiency of your home and make it a cosy, pleasant place to live is to improve the insulation. Harrison's home was damp and drafty, so she insulated all three exteriors walls and the loft space with wood-fibre insulation. "It's a bit like wearing a big duvet," she says.
Sash windows present a problem to period homeowners reluctant to replace them with ugly PVC frames and double-glazing. Harrison replaced her sashes at the front and back of the house, keeping the original window frames and filling the gaps with argon, the favourite thermal insulator in energy-efficient windows. A dormer window was fitted in the attic and high-performance windows in the bedrooms and ground-floor extension, all of which open outwards. "You can sit by them in winter without even feeling that you're by a cold window," she says.
Thanks to these heat-conserving measures and a wood-burning stove in the living room which the Harrisons feed with wood felled by tree surgeons, and which would have otherwise gone straight to a landfill site, they rarely need to switch on the central heating, using it only for an hour or two in the morning and evening during winter.
Water efficiency is also key to making substantial carbon savings. Harrison collects rainwater in three butts to use for gardening and cleaning. Diverters have been fitted throughout the plumbing system for "grey water" – lightly used water from baths or showers – which can be redeployed in the garden instead of lost down the drain. There are regulators on all the taps so water sprays out rather than gushes. "But it's never a mean trickle," says Harrison. "We're reducing the amount of water without reducing the efficiency."
Lavatories which flush with less water have been installed throughout the property. Standard lavatories use between eight and 15 litres of water per flush, though new regulations limit this wastage to six litres. The Harrisons' lavatories use either four litres of water or 2.5 litres for a reduced flush, which is impressive savings when you consider that one third of the water people use in a house disappears down the loo.
In addition, two square metres of solar panels were fitted on the roof, reducing the cost and energy of heating water by about 75 per cent. In the summer, Harrison doesn't need any gas at all to heat water, but she did have to install a new water tank, which could take both the sun and gas-heated water, at a cost of about £4,000.
Other green measures include sustainable oak flooring, which do away with the nasty toxins that come off new carpets, and clay plaster and paints. To the landing – a dark and tricky spot – Harrison has fitted a sunpipe which brings light down from the roof.
Many homeowners would happily spend what Harrison has on green improvements on a new kitchen. Not only has she added value to the property (which will become much more apparent in coming years) but she has cut her bills dramatically, now paying about £8 a month for water and £12 for gas.
Harrison runs an eco-refurbishment consultancy business and, with the SEA, is putting together a list of builders and advisers to make it easy to follow her example. "You don't need to do it all in one go," she points out. "You could do it room by room as you decorate, or just improve the windows on the colder side of your house."
It is easy to blame big businesses for hefty carbon emissions, but in fact one third of Britain's total emissions come from housing, so our green behaviour should start at home.