2/20/2015

Energy-Efficient Vs Traditional Homes: 4 Key Strategy Differences in Building an Energy-Efficient Home

I’m visiting Ecuador at the moment and I’ve been struck by the fact that most of the homes on the coast and in Quito have no heating or air conditioning system. Straddling the equator, much of the country has a relatively mild climate, with a wet and dry season. This allows many people to have a small energy footprint. Relying on ventilation from windows and doors alone, homes are relatively comfortable throughout the year.  This is not the case in the United States, where most people heat or cool their homes much of the year.

Back in Midcoast Maine, we live in a high-performance house in Belfast Ecovillage, a 36-unit community built to the Passive House standard (but not certified). While neighbors in our cold climate pay thousands of dollars to heat their homes, we pay just a couple hundred.  Our home house has generous amounts of insulation, triple-pane windows and doors, and is air sealed, so little heated air escapes to the outside. Because the home is nearly airtight, we have a Zehnder heat recovery ventilation system to continuously bring fresh air into the home, while recycling the heat from the exhaust air.  Numerous qualities set high-performance homes apart from their code-built counterparts.

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Photo courtesy of Steve Chiasson

Lots of Insulation

Our home is super-insulated compared to typical construction, from the bottom up. Insulated rigid foam is added to the slab, while cellulose insulation fills the stud walls and the trusses under the roof.  The walls also contain structural insulated panels (SIPs), which consist of a foam core surrounded by oriented strand board, resulting in continuous insulation. Most homes have thermal bridges or a break in the insulation that creates a path for heat to exit the home, but the SIPs eliminate this issue.

Airtight construction

The air-tightness of a house is commonly determined by the air-change rate. This is the number of times that the air in the home exchanges with outside air each hour. If the volume of air that enters and leaves the house in an hour is equal to the heated air volume within the house, it has one air change per hour. Most homes have an air change rate of 1, 2 or even 4. In contrast, many of the homes in Belfast Ecovillage have rates below 0.4 (at 50 pascals of pressure).

“We’ve beaten the Passive House standard [of 0.6 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 0.2; that’s three times [more airtight] than the Passive House standard, which is a high standard to hit.”

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 our home has neither. Such systems don’t recycle the heat, resulting in the hot air leaving the home. Heat recovery ventilation systems are up to 95 percent efficient, conserving the comfortable room temperature and dramatically decreasing heating loads in the winter and cooling loads in the summer.

Passive Heating

Our home is heated primarily from the sun, its occupants and appliances. Sunlight streams in through our large south-facing door and windows. During cold sunny days, our 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 last winter, our home lost a mere 2 degrees daily. Nearby homes were below freezing in less than a day.

A high-performance house offers many unique features that dramatically reduce dependence on fossil fuel while providing exceptional comfort. Although many of these features have an upfront cost, they reduce the operating costs of the home throughout its lifespan.

Sarah Lozanova is a regular contributor to environmental and energy publications and websites including Mother Earth Living, Mothering, Energy International Quarterly, ThinkGreen.com, Triple Pundit, CleanTechnica, Green Business Quarterly, Natural Home, GreenBiz, Renewable Energy World, Windpower Engineering, and Solar Today.  She currently lives with her family in the Belfast Cohousing & Ecovillage