Nothing But Net: Net Zero Homes Slam Dunk Inefficiencies

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Lozanova3Less dependence on fossil fuels, freedom from fluctuating energy prices, and eco-friendly living are alluring concepts that motivated my family to explore how to make our housing more sustainable. We recently purchased a high-performance house and then installed a photovoltaic solar system, making our home net zero. We now produce as much household energy as we use over the course of a year.

To achieve our dream of a net zero home, we started out by finding a super efficient home at Belfast Cohousing & Ecovillage, a 36-unit multigenerational community in Midcoast Maine. Triple-pane windows and doors, virtually airtight construction, a solar orientation, and lots of insulation enable the homes to be heated primarily by the sun, occupants and appliances alone.

On sunny winter days, the sun gradually warms the house and the heaters remain off. Electric baseboard heaters kick on as needed, primarily at night or on cold, cloudy days. The home is all electric – with an electric range, hot water heaters, and space heaters. This allows us to be truly net zero. Because we don’t use propane, natural gas, wood or heating oil (which is very common in Maine) and our home is very efficient – a solar system can produce all the energy that our home consumes.

True indoor air quality

Our home has a Zehnder heat recovery ventilation system to ensure high indoor air quality and comfort. Some of the earlier high-efficiency homes didn’t have high air quality because there wasn’t ample ventilation, causing moisture problems to develop. Because the home is airtight, mechanical ventilation is essential for fumes and moisture from showers and daily activities to exit the building. Just as important, an airtight home also needs a ventilation strategy for the incoming air.  By incorporating a heat recovery ventilator, the constant stream of fresh incoming air is filtered and then preheated – pulling the heat from the exhaust air.

Our home does not have exhaust fans or a vented hood over the range. While these effectively vent stale air and fumes out of a home, they are not energy-efficient in our climate because the heat is not recycled when the air leaves the home. Our heat recovery ventilation system recovers a vast majority of the heat, keeping our electricity use down. Zehnder systems are up to 95 percent efficient, allowing our home to achieve both a high level of energy efficiency and indoor air quality that wouldn’t be possible otherwise.

Before installing a solar system, we identified how we could further minimize our electricity use. This is an important step because it allows us to install a smaller system, while still realizing our net-zero goal. We swapped out halogen and incandescent light bulbs for LED bulbs, installed a low-flow shower head to lower the energy associated with our hot water consumption, and removed the screens from the south-facing windows in the winter for greater solar gain.

Go big or and go home

DSC02589Last summer, we helped organize the largest community solar purchase in Maine for our ecovillage neighborhood and we installed solar panels on our home. Because the Belfast Ecovillage homes are so efficient, a relatively modest solar system can generate all the needed power over the course of a year. Some of our neighbors with similar homes installed solar systems a year or more before us, which helped us estimate the size our system. The West residence realized their net zero goal last year with a 4.3 kW solar system for a 1,300 square foot home and the McBride residence generated 95% of its power from a 2.6 kW solar system last year. These homeowners however were willing to reduce their home energy use by keeping the heat on lower temperatures and even turning off the hot water heater when not in use.

All of the Belfast Ecovillage homes are connected to the power grid, eliminating the need for batteries. This means that we have power night and day. Our local power company has a net metering program, making the solar system more cost effective. On sunny days, our system supplies surplus electricity to the grid, and the energy credits are banked in our account. When the sun isn’t shining, we use electricity from the grid.

It’s gratifying to know that we are harvesting the clean energy that falls on our home, passively with large southern windows and actively with a photovoltaic solar system.  Even in our cold Maine climate where most homes are heated for six or seven months of the year, all our energy needs are met by an energy-efficient design and solar electricity.

Images courtesy of Sarah Lozanova

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Sarah Lozanova

Sarah Lozanova is a renewable energy and sustainability journalist and communications professional with an MBA in sustainable management. She is a regular contributor to environmental and energy publications and websites, including Mother Earth Living, Earth911, Home Power, Triple Pundit, CleanTechnica, The Ecologist, GreenBiz, Renewable Energy World and Windpower Engineering. Lozanova also works with several corporate clients as a public relations writer to gain visibility for renewable energy and sustainability achievements.
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