A Homeowner’s Path to a Zero Net Energy Home

By Mary Kraus Gazette Contributing Writer

Wouldn’t it be great: A home that produces as much energy as it uses. No utility bills. Maybe some income for energy production. And the knowledge that you have reduced your ecological footprint and impact on global warming. It used to sound like a dream, but now that dream is well within reach. How do I know? I’m living it! And it didn’t take much to get there.

A small confession: I had additional motivation to renovate our home to zero net energy. As an architect specializing in sustainable design, I have always found that living in my own experiments gives me a deeper level of insight. But the homeowner in me is also enjoying the benefits of this investment. It is a great deal, not even counting the contribution to the greater good. Our house is now more comfortable, we have no utility bills to pay each month and we receive tax-exempt income from selling our solar renewable energy credits (SRECs).

We began with an already energy-efficient home, our half of a duplex in our cohousing community. We had built with a solar-ready south-facing roof, free of any penetrations. This was a good starting point.

Regardless of the specific project, though, the path to zero net energy involves a few straightforward steps. In simple terms, you do everything feasible to reduce energy consumption, then provide a renewable energy source to cover the remaining needs. Typical steps include:

Our first step was to analyze the existing conditions and identify the most cost-effective areas for improvement.

One of my favorite green design maxims is: “Don’t overlook the mundane.” Our first, and possibly most cost-effective, move was to replace our old refrigerator, saving us an estimated 260 kilowatt-hours a year— 7 percent of our pre-renovation electricity usage. Our next move was to test for air infiltration and seal leaks. Then we moved on to the more costly strategies.

We upgraded our ventilation to a heat recovery ventilation system; in this simple device, fresh, cold incoming air recovers heat from stale outflowing air, retrieving at least 50 percent of the heat. We replaced our gas-fired boiler with air-source heat pumps. These are essentially air conditioners working in reverse. We already had solar hot water, but it was backed up by the gas-fired boiler. Our new backup is a super- insulated electric hot water tank.

Voila! All of these changes cut our non-renewable energy consumption in half, to 550 kilowatt-hours (kwh) per month for heat, ventilation, hot water backup and plug loads. Now all we had to do was provide a renewable source to balance out our yearly electrical usage. We covered our south-facing roof with high- efficiency photovoltaic panels—a 5.9 kilowatt array providing 7,000 kilowatt-hours (kwh) annually. In the first year, we produced 430 kwh more electricity than we needed—enough to run an extra refrigerator.

Our initial cost was just over $62,000. We received $11,500 in rebates and were eligible for $15,600 in tax credits. So our net project cost was $35,000. Our yearly savings on utility bills is at least $1,500 (based on current rates), and we are receiving about $2,400 in solar renewable energy credits each year. This all adds up to a nine-year payback.

So how is this relevant to your particular home? Every home is different, and every household has its own requirements. If you have shabby old siding, that might present the perfect opportunity for installing exterior insulation while upgrading your siding. If your heating system already needs replacement, it might not be a stretch to install a heat pump. If you don’t have the cash on hand to invest in a photovoltaic array, there are options for special loans, and leases are now available with little or no money down. You don’t have to do everything all at once. You can make large steps towards your zero net energy dreams by improving your building envelope and replacing some old appliances. Looking carefully at your personal goals, the specific attributes of your home, and the constraints of your budget will help in identifying which opportunities are a good fit. Whatever you do, it can be a large step in the direction of a greener world.

Mary Kraus is a partner in Kraus-Fitch Architects, Inc. in Amherst.

Earth Matters, written by staff and associates of the Hitchcock Center for the Environment at 525 South Pleasant St., Amherst, appears every other week. For more information, call 413-256-6006, or write to us.

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