Eco house that costs just £50 a year to run proves a hot property
Research has shown that Yorkshire’s pioneering Passivhaus is a star performer whatever the weather. Sharon Dale reports
IN the bitter winter of 2010 when the temperature plummeted to minus 18 C, Geoff and Kate Tunstall were sweating cobs and throwing open windows to cool down their super-energy efficient home.
They had made the mistake of turning up the only heat source in their three-bedroom detached house: a single radiator in the sitting room.
“It was our first winter and we had no idea how the house would react. In fact it wasn’t just fine, it was too good. When we turned the radiator up slightly we were far too hot.,” says Geoff.
The Tunstalls moved into the pioneering property in Denby Dale two-and-a-half years ago.
It is the first Anglicised version of the German Passivhaus, combining British materials and construction techniques with a German software package that ensures maximum effectiveness.
It works on a simple tea cosy effect and relies on clever design, orientation towards the sun, careful construction and insulation three-and-a half-times greater than required by building regulations.
No draughts can get in and no heat can leak out of the building, which is 15 times more airtight than the average new home.
The atmosphere is never stale and condensation is no problem, thanks to a mechanical heat recovery ventilation system that brings in fresh air from outside and warming it using 99 per cent of the heat from the outgoing air
The ground-breaking development by Huddersfieldbased Green Building Company, has been closely monitored by Leeds Metropolitan University’s Centre for the Built Environment.
Their research on everything from energy consumption to internal temperature and humidity have just been published and prove that the British-style Passivhaus performs just as well as its forbears in Germany and Austria, which are built using insulated panels.
Chris Herring, director, Green Building Store and technical leader on the Denby Dale Passivhaus project, is thrilled.
He says: “We are delighted that the house is performing as expected and as it was designed. That is the beauty of the Passivhaus approach to low energy building, it has been tried and tested for over 20 years and the modelling software has been continually refined and improved so that it can accurately predict how the building is going to perform. This is in contrast to other approaches to low energy building which promise much but often have a performance gap when actually occupied.”
The only minor issue was learning how to use heat recovery and ventilation system, which was soon accomplished, according to Geoff, whose motivation was to create a home that was cheap to run in his retirement.
The three-bedroom property, built in the garden of the Tunstalls Victorian cottage, cost about £141,000. Passivhaus properties costs about 20 per cent more to construct than an average new-build because of the attention to detail, but they use 90 per cent less heat energy than a standard UK dwelling.
The Tunstalls have just the one radiator, which is only on for four hours a day in the depths of winter. Warmth is generated from the sun through windows, cooking and body heat. Having ten people in the house creates the energy equivalent of an electric fire.
The idea is to maximise heat gain and minimise heat loss, so the insulated house has tripleglazing with large windows on its south facing front and small ones at the cold, north-facing rear.
Any gaps are minimised during construction and insulation has to be continuous.
Areas liable to settlement cracks are sealed with special air tightness tape to prevent cold air seeping in.
There are no plug sockets on the outside walls and no lights in the ceiling, so the envelope and insulation barrier isn’t punctured.
Last year, the Tunstalls heating bill was about £120. The total gas and electricity costs were £600 but this was offset by a £550 annual feed-in tariff from the Government as a reward for installing solar hot water panels.
“It’s remarkable. The energy bills for our old house cost about £1,800. Now we pay £50 a year,” says Geoff.
“But that’s just the money, we are also delighted with the comfort and the feel of the house. It’s so restful and serene and the temperature is a constant 21C.
“There are no no cold spots or draughts and there’s no damp. You are breathing in filtered fresh air and there is low humidity so it never feels stuffy. It’s a very healthy environment,especially for anyone with asthma or bronchitis.”
He is also thrilled that their selfbuild project has sparked interest from all over Britain and helped raise the profile of the Passivhaus concept.
There are now around 150 developments in the commercial and residential sectors with another 500 expected to get underway.
“We’re thrilled that we’ve been pioneers and that the idea has mushroomed. It makes perfect sense to build in this way and everyone who has visited us here can see that.
“All in all it’s an inspirational house that makes you feel good and then when the bills come you feel good again.
“The only problem we have is that it’s so comfortable it has spoilt us for staying anywhere else.”
COST EFFECTIVE: The Denby Dale Passivhaus uses 90 per cent less heat energy than the average new build, thanks to its airtight construction. Owners Kate and Geoff Tunstall say it saves them money and gives them a comfortable and healthy home. The house has just one radiator, which is only used in the depths of winter.