How to build a net-zero chalet

Jonathan Heroux sold his ski home in Breckenridge, Colorado, in 2019, and was missing it. Last year, when flicking through the local ski press from his home in Denver, it struck the 54-year-old investment banker how to find its replacement. Electric Pass Lodge, a new apartment project, located in the Aspen Snowmass resort, was trumpeting its environmental credentials — including high-tech draught-proofing, savvily positioned glazing to trap the sun’s heat and electric heating systems powered by renewable energy.

“You want to do something about [climate change] but when you’re buying a home it’s hard. This building looked like it was making a genuine impact — at the same time, it felt like an investment in a good location,” he says. In April 2021, he put down the deposit for a $1.46mn two-bedroom flat, which will be completed next spring.

It may not rival length of season or how long the pistes are, but for some ski property buyers, how a home is built and run, and the eco-credentials of the resort in which it is located, are climbing up the list of priorities — especially since climate change is threatening the viability of some resorts, due to reduced snowfall.

“Like the social impact of their housing choices, the ecological footprint of their home is increasing in importance for buyers,” says Brian Dunbar, director of the Institute for the Built Environment at Colorado State University. “Local authorities are growing the incentives for building and running homes [with low environmental impact],” he adds.

Some remain sceptical of the premise. Building and running properties — which in most cases are second or third homes used a few weeks or months a year — at altitude is a resource-intensive business. Those serious about cutting their carbon footprint might favour hotels and, in most cases, ski homeowners’ tastes haven’t yet shifted to buying or building smaller homes: the most effective way to reduce their emissions footprint.

“How is a 20,000 sq ft home in Aspen sustainable when it’s a third or fifth home?” says Jeff Dickinson, an architect at Energy and Sustainable Design, a practice based in Carbondale, Colorado. Nonetheless, he is adamant that demand for resource-efficient homes, which can be heated and run without adding to emissions, is increasing. “That’s what it’s all about now, everyone is asking me: ‘how can I get a net-zero home?’”

Insulation is a good place to start. Dickinson is currently building a home using straw bales in place of fibreglass insulation to fill out the traditional wood post and beam framing — and is about to begin three more. He says they are more than twice as effective at retaining heat.

“But it’s not just about the walls, you might be thermally disconnecting the building completely from the ground,” says Steve Novy, who runs Green Line Architects in Carbondale. He says he often builds houses on two or three inches of blueboard or mineral wool — insulation materials with good compressive strength — to keep the house from losing heat to the ground.

In April, Dan Wood and his wife Lisa, both in their fifties, moved into a newly built home in Golden, a small town about 60 miles west of Banff in Canada’s Rocky Mountains. He has designed his home to Passivhaus principles, meaning the building is virtually air tight, keeping the loss of heat to a minimum. The home has a heat pump, which provides warmth in the winter and cooling in the summer, and an energy-recovering ventilation system, which warms and moisturises incoming air with heat and humidity drawn from outgoing air.

Highly efficient household goods further limit electricity draw, such as a heat pump-powered clothes dryer, whose hot air is retained and recycled within the appliance rather than exhausted outside.

Since the Woods moved into their new home, their electricity bills have been roughly a fifth of those in their last house in the nearby city of Calgary. “We’re at $3 per day at the moment for all electricity and hot water.”

With bills this small, there is less incentive to install solar panels. But he plans to spend a year or two investigating what his power consumption is — so he knows how many solar panels he might need — and will consider installing them to take the home entirely off-grid.

All homeowners should be looking to replace gas with electricity for heating and cooking, says Carol Dollard, an energy engineer at Colorado State University. At her home near Fort Collins, a Colorado town at more than 1,500 metres above sea level, she heated her water for 30 years using solar panels. They failed in 2012, following huge forest fires that forced her to evacuate for a month. Since she returned and renovated the property, the home has been all-electric.

Electrifying the housing stock and switching to a renewably powered grid is a much more efficient way to reduce carbon emissions than having individuals invest in solar panels or micro hydro power generators, she says. By 2030, Holy Cross Energy, the utility company that operates the local grid, plans to source all its energy from clean or renewable sources.

Electric heating from a renewable grid will make a big dent on a mountain home’s carbon footprint, but even better is to build one heated by the sun. For one home Dickinson built near Carbondale, stretching the house along an east-west axis and concentrating windows on its south side resulted in roughly half the home’s heat being generated by the sun, he says.

“It meant placing the living, dining and kitchen on the south side of the home and the functional spaces — the laundry, bathrooms, mechanical rooms and pantries on the north,” he says.

Passive solar design is not a new concept, he notes: the Anasazi native American people who lived across south-western Colorado often settled south- facing cliffs.

Window positions and shading is crucial if mountain homes aren’t to overheat in summer, meanwhile. Constructing shading over south-facing windows minimises overheating when the summer sun is overhead and hottest.

Opening windows during cool summer night also helps compensate for the daytime heating effect of the sun. “It’s a little cooler in the mornings and you might need to put a sweater on,” he says.

But for Dollard the biggest obstacle to greener mountain homes remains the obsession with size.

“What’s really needed is a change of attitudes about how we live,” she says. “People talk about wanting a big house to entertain in, then you find out they do it maybe six times a year. If it’s a second home, don’t make it bigger than you need. Make it a cosy little space.”

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