D. Whitwell Way, Coton
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Impressive largely DIY retrofit by Cambridge 2030 speaker Bart Hommels using a detailed scientific approach. Includes passive house standard extension, super-insulated floors, walls and roof, state of the art weather compensation boiler, PV array.

Open: 22nd & 28th September
Type: Renovation
Built: 1945

Further information

From Bart and Rose: “When buying the house in 2011, we knew it would require a lot of work to bring it up-to-date. When realising how much energy was required to provide hot water and keep the house warm in winter, I (Bart) got more and more interested in the energy consumption of homes and how ours could be improved.

When we (Rose and Bart) decided to go ahead with having an extension built, I (Bart) wanted to have this built to Passivhaus standards since the extension should not increase the energy consumption, but act as a starting point for a whole-house thermal improvement project instead. The architects, Eco Design Consultants, did the Passivhaus calculations, designed the extension and provided an options report which sets out the steps required to achieve different levels of energy efficiency: AECB Silver, EuroPhit and PassivHaus EnerPhit.

The changes have been enormous. The extended living space has transformed the house, and the levels of comfort have improved beyond recognition. Draughts are largely gone, and the house is at an even temperature throughout, and stays cool in summer.

The CO2 footprint of our house has reduced by about 60%, or 1.5 tonnes per year, with potential for more. The house is now much more comfortable, while energy use for heating has gone down by 70%. Looking at the numbers is one thing, experiencing it is quite another!”

Key features

  • Single storey extension built to Passivhaus standards
  • Kitchen floor and living room floor taken up and all replaced with super-insulated screed floors with wet underfloor heating (UFH) throughout.
  • 200mm polystyrene External Wall Insulation (EWI) on rear and side of existing house with front facade pending. 100mm EWI to 300mm below DPC.
  • 2.88 kWp solar PV array, with diverter for heat store immersion element to supply domestic hot water.


Read the full case study




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