This Maine home can stay 70 degrees without a furnace, even when it’s freezing outside

What if you could design a house that on a cold day in January would stay at 70 degrees inside — without running the furnace? Or even having a furnace?

It’s already being done.

In fact, what’s known as the passive house concept came to the United States in 2006, and is being used to construct buildings throughout the U.S.

Maine Public recently visited a passive house in the town of Hope to find out how it works — and what it costs.

This story is part of our series “Climate Driven: A deep dive into Maine’s response, one county at a time.”

It’s 31 degrees outside when Patrick McCunney greets a reporter on the porch of his newly built passive house.

He moved here from Philadelphia with his wife, Madeleine Mackell, and their two young daughters a little over a year ago, and the couple says that they decided to build the 1,500-square-foot, two-story New England farmhouse-style home knowing that they would save money on energy over time.

While it was 31 degrees outside, the inside was much cozier.

“It’s about 70 degrees in here,” McCunney, who is a mechanical engineer, says. “And once you set that temperature the house, because of its airtightness and amount of insulation, it maintains that temperature pretty efficiently.”

And do they have a furnace?

“No furnace,” he adds. “Just this small little heat pump. Relying a lot on the sun to heat, which in the winter is pretty amazing.”

The sun streams in through a wall of windows on the south side of the home, and onto a rooftop solar array that McCunney says on bright days like this will generate four times as much energy as the house needs.

That means that the only heat or electricity bill they pay in the winter is the connection fee to Central Maine Power — about $13 a month.

“We wanted it to be a sustainable design and materials and the fact that we only have to pay $13 a month for our connection fee is just an added bonus,” Mackell says.

McCunney adds, “Also with a passive home, you’re severating yourself from the volatility of the energy world and what that brings and unknowns as we enter into this new warming planet and sort of provide some buffer against that chaos.”

The builder of this passive house, Alan Gibson of the Belfast-based firm GO Logic, says he co-founded the company specifically to specialize in passive structures that would appeal to buyers seeking energy efficiency

“Absolutely, along with other benefits including comfort and resilience and durability come along with it,” he says. “It’s just that first cost issue that everyone stumbles on.”

Passive homes, Gibson says, do cost about 10% more to build than conventional structures, simply because they have more stuff in them.

“There’s more insulation, there’s more care taken to make sure they are airtight, there’s the ventilation system, there’s better windows and doors. And people have a hard time getting beyond that even though we can show them pretty easily that the economic payback is there,” he says.

So, let’s look at the math. Say a conventional single family home that’s up to code costs $400,000. A similar passive house would run about $40,000 more.

Most of that extra cost goes into the 15-inch thick walls, with multiple layers of insulation and sheathing, high-performance triple-glazed windows and doors, and a ventilation system, which is critical in an airtight building to allow it and its inhabitants to breathe.

Gibson says it’s designed to bring in fresh air from outside, but retain much of the heat.

“And it has a heat exchanger in it that recovers almost all of the heat that’s being sent out and transfers that heat energy to the incoming air,” he says. “So your incoming air is not 20 degrees if it’s 20 degrees outside. It’s warmed up to about 65.”

And Gibson says in addition to the huge reduction in carbon emissions from not burning fossil fuels for heat, GO Logic’s passive homes are constructed of wood and agricultural-based materials that are carbon friendly.

There are more than 100 passive houses in Maine. But even advocates of the design standard acknowledge that it is not really best-suited for single family homes.

“If you can afford that, and that’s what you want to do, there’s no downside. I’ll say that,” says Naomi Beal, executive director of passivehausMAINE, a nonprofit that for the past decade has been working to help grow the use of passive house design, particularly for larger structures.

She says that’s where the cost-benefit equations for the standard make the most sense.

“The German model has always been for larger buildings. For multi-families, for commercial projects of all sorts: hospitals, prisons, dormitories. There’s not a barrier of cost at that level usually,” Beal says.

“There’s not extra expense at that level,” she adds. “It’s just a matter of knowing how to do it.

And there are a growing number of larger passive buildings in Maine, including the 218,000-square-foot Portland Residence Hall under construction at the University of Southern Maine, which will be the second largest passive house university building in the country.