My family experienced a five-day power outage last December after a Maine ice storm. The temperature of our neighbor’s house dropped to near freezing after one night. Despite having below freezing temperatures, even subzero weather, our house remained pretty comfortable. The indoor temperature dropped by only 2 degrees daily, with no supplemental heat. While neighbors scrambled to hook up generators and space heaters to keep the pipes from freezing, we knew our house wouldn’t freeze. What is our secret?
We live in a house where the design was guided by the Passive House Standard at Belfast Cohousing & Ecovillage. “Build it nice and tight, face it to the south, not towards the road, and put most of your glass on the south,” explains GO Logic foreman John White. GO Logic, the builder of our house has designed and constructed two Passive House-certified homes in Maine.
The solar orientation and south-facing windows make a noticeable difference on sunny days. During the only sunny day of the outage, the indoor temperature in our home increased by 7 degrees. Even with the temperature below zero outside, our indoor temperature will increase by 5 to 10 degrees Fahrenheit throughout the course of the day. With a solar system, the homes can be near net-zero, meaning that the solar array can generate as much as the house consumes over the course of a year.
On sunny winter days, our home can easily gain 10 degrees from the sun alone. Because the angle of the sun is lower in the winter, the sunlight streams in. During the summer, the sun is higher in the sky and doesn’t heat the space as much. Although the builder, GO Logic, believes the house meets the Passive House Standard, it has not been certified.
Passive House Standard for an energy-efficient home
This standard ensures houses meet a set of criteria for space-heating energy demand, primary energy demand and airtightness. GO Logic uses a blower door test to ensure the house performs to the Passive House Standard of less than or equal to 0.6 ACH at 50 Pascal pressure. That means that there would be fewer than 0.6 air-changes per hour in the house with a 50 Pascal pressure, which is five times the pressure our house is likely to experience on a cold winter day.
Passive House Standard is popular in Europe, where 15,000 homes have been constructed in the last 10 years. As is often the case with energy efficiency, the Passive House Standard has been much slower to catch on in the U.S. However, it has furthered the green building industry by quantifying the impact of energy-efficient building materials.
“The people at Passive House took [energy efficiency construction] ideas and were much more scientific about the physics of how buildings work,” says Alan Gibson, a principal of GO Logic. “It is revolutionary in that it has spawned a new way of thinking around high performance buildings.
“The biggest thing they developed was the energy model spreadsheet that determines how much energy a building gains or loses. It’s all based on physics and math.You have a section of wall with certain properties and materials, and you can tell how much heat is going to move through that wall over time. If you put that all together and determine every way a building can gain or loose energy, you create a comprehensive model for how a building is going to perform.”
Gibson believes that quantifying the properties of energy efficient building materials helps boost the market for these materials. “If you have a triple-glazed window and you compare it to a double-glazed window, you can quantify the difference in durability, comfort and moisture,” explains Gibson. “All of a sudden, people wanted more triple-glazed windows, so the industry responded by producing more. When supply increases, they become cheaper.”
Indoor air quality
“I think the Heat Recovery Ventilation (HRV) system is what revolutionized these houses,” says Brian Hughes, a carpenter for GO Logic. “People have been building super-tight, insulated houses since the 1950s. The problem was that the air quality wasn’t good and people didn’t try having a super-tight buildings again until they figured out that with the heat exchanger, you can use a tiny bit of electricity and have really high air quality.”
Our house has a Zehnder HRV system, which brings in filtered outside air and captures heat from stale indoor air before it leaves our house. Airtight homes need fresh air to ensure high indoor air quality and avoid humidity and mold issues. HRV systems are an energy-efficient solution that ensure excellent indoor air quality, while capturing up to 90 percent of the heat.
“There is the pocketbook savings [associated with a high-performance house], but there is also the social aspect of it too–making a conscious choice to live in a more sustainable house,” adds White. “We are not conditioned to think that way. We are conditioned to think it’s private property and I can do what I want, as long as I’m not breaking the law. If gas is cheap, why would I care how much I use?”
Image Credit: Belfast Cohousing & Ecovillage
Sarah Lozanova is a regular contributor to environmental and energy publications and websites, including Mother Earth Living, Green Building & Design, Triple Pundit, Urban Farm, and Solar Today. Her experience includes work with small-scale solar energy installations and utility-scale wind farms. She earned an MBA in sustainable management from the Presidio Graduate School and she resides in Belfast Cohousing & Ecovillage in Midcoast Maine with her husband and two children.