Blogs, Energy Efficiency

Energy-Efficient Vs Traditional Homes: 4 Strategies for a High-Performance Home

New England has experienced one of the most intense winters in recent history. Relentless snow hampers travel, winter weather advisories are frequent, and huge snow drifts obscure cars.

Such weather makes me grateful to live in a high performance house in Belfast Ecovillage, a 36-unit community built to the Passive House standard (but not certified) in Mid-coast Maine. While neighbors in our cold climate pay thousands of dollars to heat their homes or must keep the thermostat down out of economic necessity, we pay just a couple hundred dollars. Our home has generous amounts of insulation, triple-pane windows and doors, and is air sealed, so little heated air escapes to the outside or unheated air enters our home. Because the house is nearly airtight, we have a Zehnder heat recovery ventilation system to continuously supply fresh air into the home, while recycling the heat from the exhaust air.  Numerous features set high performance homes apart from their code-built counterparts.

Airtight construction

The air-tightness of a house is commonly measured by the air-change rate. This is the number of times that the air in a home exchanges with outside air each hour. If the volume of air that enters and exits the house in an hour is equal to the heated air volume inside the house, it has one air change per hour. Most houses have an air change rate of one, two or even four or more. In contrast, many of the homes in Belfast Ecovillage have rates below 0.40 (at 50 pascals of pressure).

“We’ve beat the Passive House standard [of 0.60 air changes per hour] by far in all the houses at Belfast Ecovillage,” explains Brian Hughs, a member of Belfast Ecovillage and carpenter for GO Logic, the design-build firm that served as the general contractor. “The triplex unit got less than 0.20; that’s three times [more airtight] than the Passive House standard, which is a high standard to hit.”

Lots of insulation

Our home has generous amounts of insulation compared to typical construction, from the bottom up. Rigid foam is added to the slab, and cellulose insulation fills the stud walls and the trusses under the roof. Structural insulated panels (SIPs), which consist of a foam core surrounded by oriented strand board are attached to the frame, resulting in continuous insulation. Most homes have thermal bridges, or breaks in the insulation where heat exits the home, but the SIPs eliminate this issue.

Ventilation

Most leaky homes still rely on an exhaust fan in the bathroom and a vented hood over the range for humidity and fumes to exit the home, but Belfast Ecovillage homes have neither. Such ventilation systems don’t recycle the heat, resulting in hot air venting out of the home. Heat recovery ventilation systems are up to 95 percent efficient, conserving the comfortable room temperature and significantly decreasing  both heating loads in the winter and cooling loads in the summer.

Passive heating

Our home is heated primarily from the sun, occupants and appliances. Sunlight streams in through our large south-facing door and windows. During sunny winter days, the heating system is off throughout the day, with the home remaining warmer than the thermostat setting.  During an extended power outage with below freezing and some sub-zero temperatures in 2013, our house lost a mere 2 degrees daily. Nearby homes were below freezing in less than a day.

A high-efficiency house offers many unique features that dramatically reduce fossil fuel use, while providing exceptional comfort. Although many of these features do come with an upfront cost, they reduce the operating costs of the home throughout its lifespan.

Photo credit: Belfast Ecovillage