Greenhomebuildermag Magazine: Features

Use these tips on building a net-zero energy home.
By Stacy Hunt

While having a home that is energy self-sufficient may seem like a futuristic dream, today it's possible for anyone to build a home that produces as much energy as it uses. The net-zero energy home (NZEH) is a well-built, high-performance home that employs a combination of energy conservation measures with onsite renewable power generation to break even on energy use. Building a home that produces as much energy as it uses is no easy task. The home must address a series of factors that traditional homes often ignore. Not only does the home have to be super energy-efficient, but it must also incorporate renewable energy generation systems. On-site power from renewable sources can be solar, wind or geothermal, but often a combination of sources is required to achieve an NZEH.

Through their Builders Challenge initiative, the U.S. Department of Energy (DOE) has assertively started to promote net-zero energy homes. The approach fostered by the Builders Challenge is that a NZEH must do more than simply break even on power usage -- it must also meet the stringent quality criteria of a high-performance home. These standards require third-party verification to confirm that the home actually performs as expected and exhibited. After a full inspection, a home must meet the quality criteria and score a zero on the Home Energy Rating System (HERS) Index.

To successfully build a net-zero energy home, builders should consider these factors:

Use natural elements to reduce the energy load. A home's orientation, incorporation of broader eaves and natural cooling strategies are all elements builders can use to reduce energy load. Smaller homes naturally use less energy, so a NZEH home will have a small footprint than a traditional home.

Utilize more insulation by increasing the insulation values in the foundation, walls and ceilings is also an impact. As part of the insulation strategy, proper air sealing is critical and added ventilation strategies are needed to ensure good indoor air quality.

Builders must pay attention to the sizing of mechanical systems and the home's lighting strategy and choose

energy-saving appliances. Ground-source heat pumps and evaporative cooling units can offer homeowners a comfortable living space while using less energy. Fluorescents generate less heat which can lower energy use for cooling in warm climates.

Affordable strategies for onsite power generation. With tax incentives and rebates now being offered, generating power onsite can be more affordable. Proper sizing and installation of equipment is important. Combining passive solar collectors to generate hot water and photovoltaic (PV) panels for electricity is the most common approach to achieve a NZEH on a budget.

No matter how great the home, it will not achieve zeroenergy use without consistent conservation measures taken by the homeowner. In addition to lowering the thermostat to a reasonable temperature and shutting off unnecessary lights, active maintenance and upkeep is critical. Even though high-performance homes are built to be more durable, regular servicing of the heating and cooling systems and appliances are necessary for the home to perform well over time.

A NZEH does not mean that the home is completely energy independent all the time. During extreme weather conditions, the home will have to draw energy from the local power grid to keep the occupants comfortable. However, over the course of a year, a NZEH will use as much energy as it generates and can supply the local grid with the surplus electricity it creates.

The Builders Challenge initiative set a goal of having affordable NZEH homes available in all markets across the United States by the year 2030. Along with Building America, the Builders Challenge website offers support for builders interested in building NZEH homes.

Stacy Hunt is a senior consultant and project manager with Confluence Communications and is a consultant with the Department of Energy. She may be reached at stacy@confluencec.com.