When West Yorkshire residents Geoff and Kate Tunstall decided to build a cottage on their property that would serve them well in their retirement years, they found themselves edging closer and closer to the energy efficiency and interior comfort typically attained by Passivhaus construction.
And, well, a Passivhaus home – with a nod to Britain’s traditional wall-construction vernacular – is what the Tunstalls are in fact getting.
The project, known as the Denby Dale Passivhaus, is being managed by Bill Butcher, a builder and co-founder of green-building supply company The Green Building Store, based in the Bolster Moor area of northern England’s Pennine Mountains, not far from the Tunstalls. Butcher told The Daily Mail that a couple of early designs for the home didn’t perform to Passivhaus standards when modeled on Passivhaus Planning Package software. But the final design – which includes cavity-wall construction and stone cladding typically found in the UK – met the standards entirely, and should be energy efficient enough to keep the Tunstalls’ annual heating bill under $120.
The case for cavity-wall
Butcher noted that while cavity-wall construction materials are quite different from the wall construction components typically used for Passivhaus homes elsewhere, the former is far more familiar to builders in Britain and can be reliably insulated to the required thermal resistance and airtightness.
“You can buy a Passivhaus flat pack from Germany, but the materials are completely different,” Butcher noted. “They use a solid wall and stick polystyrene insulation on the outside of the house, they don’t fit into the local streetscape here, builders aren’t familiar with them, and planning can be an issue. This Passivhaus is the first to be built using British construction methods, with blockwork, a cavity wall, and stone cladding.”
The 1,270 sq. ft. of the three-bedroom house – which is being built in the garden of the couple’s Victorian home and is due for completion in the spring – will include a heat recovery ventilator and is designed to use 90% less energy for space heating than the annual average in the UK, which is about 150 kWh per square meter. (Click here to read the builder blogs about the project, which also include reader feedback.)
But for all its thermal efficiency, as the Mail points out, the house won’t rank high on the UK government’s Code for Sustainable Homes register, mainly because points under that system are awarded for renewables like solar energy systems and woodchip boilers. Nonetheless, the project is of interest to almost everyone in the UK construction industry, for beyond its energy efficiency is its relatively low construction cost: about $227,000.