People have a chance Sunday to see the most energy-efficient house in Westport -- a dwelling that's among the most energy efficient in the United States.

"This could be the first in the U.S. to get a retrofit certification from the Passivhaus Institute," said Shannon McAvoy, a clean energy organizer with the Clean Water Action's Neighbor to Neighbor Energy Challenge. A passivhaus is technically defined as a building that achieves "thermal comfort ... solely by post-heating or post-cooling of the fresh air mass."

Tours of Doug McDonald's house on Roseville Road, however, were fully booked as of Wednesday, but future tour dates are likely to be set. Those already signed up for the tours also will have the chance to sign up for "home energy solution visits" by representatives of Connecticut Light & Power, said Pippa Bell Ader, co-chairwoman of the Westport Home Energy Challenge.

But it's unlikely anyone who signs up for a home energy solution visit will cut their energy use down to McDonald's level.

McDonald, who moved to Westport from Brooklyn in 2010, said his three-story, 4,000-square-foot house uses 90 percent less energy than a typical house. It was originally built in the 1930s by Barry Byrne, a protege of famed architect Frank Lloyd Wright. The house, made of concrete, was built for Oscar Levant, a well-known actor, musician and author some 80 years ago, McDonald said.

During an interview earlier this week, McDonald said four considerations went into creating his passivhaus -- orientation of the house and land to the sun, air tightness, insulation and mechanical ventilation.

McDonald said his house is on a hill and faces south, both of which are ideal for using the sun's energy, via solar panels on his roof, to heat water for showers and cooking.

"In this house, we're saying, `Gosh, the sun is hitting the house at 200 degrees, let's use it,' and I use it for domestic hot water and showers," McDonald said. The heat is transferred from the roof in glycol, a heat transfer fluid, to a tank in his basement where fresh water is stored.

To make his house airtight, McDonald enclosed it in blown cellulose insulation, which he said was glass infused with air. "Basically, I took a concrete house and put a huge down parka around it, and then I put in new windows and doors," he said.

But McDonald did more than simply install extra-thick doors and new windows. He made sure windows that faced south were extra large to take advantage of heat from the sun, and he lined up windows and doors with the exterior "down parka" of insulation.

"By having the windows attached to the layer of insulation, and not to the structure of the house, I decreased my heating [demand] by 50 percent. It makes it so I have no thermal bridging. When windows are touching insulation, that whole system is airtight," he said.

McDonald also removed the home's chimney and blocked up and insulated fireplaces in the house. "They just don't get blocked up so the air can't go through, they get blocked up and completely insulated," he said of chimneys in passivhauses.

Even though his house is completely air sealed -- McDonald compared it to living in a balloon or spaceship -- the Westport homeowner said he has more and cleaner fresh air coming into his house than a typical dwelling.

That is achieved by an energy recovery ventilator -- what McDonald calls "a magic box" -- on the second floor that draws air into the house from the outside and expels air from inside the house to the outside on a continuous basis. As air passes in opposite directions, the air coming into the house takes on the properties of air leaving the house, McDonald said.

"Fresh air constantly, 24/7, comes in, and the fresh air exchanges its temperature and humidity with the air that's leaving," he said. "The fresh air constantly being introduced into the house is basically the same temperature as the air leaving the house. So, if the house is 73 degrees inside and it's 20 degrees outside, I'm not introducing 20-degree air inside. I'm introducing 73-degree air inside. It's always driving toward 73 degrees and 45-percent relative humidity." The air coming into the house is filtered and then dispersed into rooms through a mechanical vent head, which resembles a smoke detector, on the ceiling, McDonald said. "There's one in every room you occupy," he said of the mechanical vent heads. McDonald also left a gap between ceilings and the highest point of furniture in rooms to enable the fresh air to circulate more easily.

In addition to 73-degree air coming into the house via the magic box, which uses 10 watts to 50 watts of energy, McDonald also heats his house by shooting fresh air over 200-degree water stored underneath a section of floor in his den. He added that 20 percent of the heat he needs in his house is provided by occupants and light bulbs.

McDonald regularly updates the temperature and humidity inside his house on a website -- -- to show that his passivhaus works. Earlier this week, the outside temperature fluctuated wildly from night to day, but the only fluctuation inside the house took place when he, his wife and kids woke up because each person, in motion, generates about 1,000 btus of heat per hour, McDonald said.

McDonald's house is not completely off the grid. He says he uses a small amount of electricity to operate the solar panels, lights, magic box and refrigerator. "At this point, I don't make any electricity," he said, adding that his monthly bill for electricity averages $120.

But McDonald added, "I have no oil bill, propane bill or gas bill. I have no bills except electricity."

"As soon as I want to add the photovoltaics, I can go to zero energy capable," he said. "In the meantime, I'm living better than everybody else. I'm living in 73 degrees, 45-percent relative humidity. It's a chemical-free house. This is a chemical free, with more oxygen, and you can feel it."

Renovating the concrete house into a passivhaus wasn't without challenges. The brutal winter of 2010-11 made it difficult to do construction because the temperature wasn't high enough to adhere blocks of blown cellulose insulation to his concrete house, McDonald said. He said he did most of the renovation work himself and that it took about a year and cost about the same as a typical renovation.

McDonald said he'd love to build another passivhaus in Westport and would like the next one to be from the ground up, instead of a renovation. He said he renovated houses before the home on Roseville Road, but not to standards of the International Passivhaus Institute. "I had done very energy-efficient [renovations], but we didn't know we could go this far," he said. "What I want to show other people is you can do this and you end up in a much more comfortable environment."

Ader said she was impressed by McDonald's house and how it operated. "I know it's not for everyone, but it's important for everyone to know this is available and can be done and is something to look to," she said.

For more information, call 203-200-0626 or visit the website,

Andrew Brophy is a freelance writer.