It’s a hot August day on a busy street in suburban Connecticut. In the sunlit living room of a spacious house, it’s quiet, bright and cool – even in the absence of air conditioning. “We use up to 90 percent less energy per square foot on heating and cooling here than in a typical home,” said homeowner Doug Mcdonald.

Americans spend a lot of time focusing on how to make homes more energy efficient – with better light bulbs, smarter thermostats, and new furnaces. But what if you could design or retrofit a home so that it uses virtually no power to cool itself down to the desired temperature?

So-called “passive houses,” like this one – a blocky eight-year-old three-floor structure set on top of a hill – are working toward this end.

Mcdonald took his cues from the Passive Haus Institute, the Germany-based outfit that pioneered these concepts. To date, most of the passive houses that have been built are in Europe, where people are accustomed to small homes and high energy costs. Comparatively few have been constructed in the U.S. But that’s changing.

Passive House construction revolves around a set of ideas that are simple in concept but difficult to execute. At its root, it involves making the house a very tight envelope – so that very little air gets in or out, except by design – taking advantage of the sun, and using the natural forces of physics to heat and cool air. Devised by nuclear physicists, the process involves constructing equations to figure out how to use much less energy. (Here’s a  formal definition of the philosophy.)

When Mcdonald was considering moving from Brooklyn to the Connecticut suburbs several years ago he “read about the work and decided [he] had to do it.” In 2010, he bought the house, a blocky home built in the 1930s on three levels, and completed the work as part of a larger renovation in about a year.

In traditional houses, unwanted and uncontrolled flows of air wreak havoc with the climate and waste a lot of energy. The first step is therefore to turn the house into an impregnable envelope. Mcdonald makes an analogy to skiing – when you hit the slopes, it’s smartest to wrap yourself entirely in a single entity, like a ski suit, rather than a bunch of different garments that leave space for cold air to enter and hot air to escape. Accordingly, one of the primary features of a Passive House is a ten-inch thick layer of continuous insulation wrapped around the outside of the house and taped together at every seam.

Next come the windows and doors. Mcdonald’s home has plenty of windows, especially on its southern-facing walls, which are best for bringing in sunlight and warmth in the winter. The windows have three panes, and fit seamlessly into their frames. There are also no gaps between the window and the house infrastructure. The same is true for all doors. In doing this, the goal is to eliminate any “thermal bridge” – or conduit that can bring in cold or hot air from outside. Mcdonald notes that if it is ten degrees outside, the outer handle of the door will be 10 degrees, but the inner handle of the front door will be 72. “In a 4,000 square foot house, the total openings in the envelope are the size of a Post-it note,” Mcdonald says. In a typical house, all the gaps, cracks, creases, and vents would create an opening as big as four sheets of plywood.

There’s another advantage of not having gaps and holes: there’s no place for water, humidity, and other forces or creatures to get in. “No mice, no mold,” as Mcdonald puts it.

The temperature can be regulated with thermostats, thanks to the last component of passive house design: a mechanical system of air exchangers that modulate temperature by pushing air in and out of the house, all while capturing and releasing heat.

Combined, these components effectively eliminate the need for heating oil, which, in a house of this size in this area, can run up to $10,000 per year. Mcdonald has a decent-sized electric bill, in part because he has fancy appliances and a steam room. “It’s not like I’m living in a tent.”

While it costs more to build a passive house, homeowners can reap rewards in the form of lower operating costs. Eliminating heating oil deliveries for 15 years can save $150,000. But Mcdonald believes that these features will also add to the value of the house – especially if new residential codes are upgraded in coming years.

To put that theory to the test, Mcdonald has started a business – Pure House – constructing large homes built using Passive House techniques. A few miles away, a 5,800-square-foot mansion he is currently constructing reveals the difference. Insulation and waterproofing surround the foundation, and insulation panels are taped extensively at every seam. The windows are installed with very tight tolerances. Inside, advanced wood-framing techniques are used to avoid having beams punch through the structure.

Mcdonald describes the house he’s building as a “wolf in sheep’s clothing.” Why? He’s trying to show potential buyers that they won’t be sacrificing anything in terms of aesthetics or feel in exchange for efficiency. And his goal is to price the home so that it is competitive with comparable homes built through regular conventional methods.

He’ll also be marketing something that is more difficult to put a price on: comfort. Mcdonald notes that he and his family don’t experience the many annoyances that plague even well-designed homes – areas that are cold in the winter, drafts seeping in at doors and windows, or the attic that won’t cool down in the summer. Plus, thanks to the thick windows, sound from the road doesn’t penetrate their home. Out there, it may be a busy New England suburb, with all the extremes of hot and cold temperatures. But inside, Mcdonald notes, “every day is Santa Barbara.”