Net zero energy homes: Ready for prime time?
Iris Price | Improvement Center Columnist | March 3, 2015
What if your home could be so energy-efficient that it consumed only as much energy as it created? Are we talking about sci fi? The Home of the Future? Utopia?
If you've never heard of the concept of net zero energy, you might be surprised that it's not only possible, but in some places, like the State of California, it will soon be required.
A net zero energy home commonly refers to one that uses renewable energy sources to offset the cost of household energy usage to the point where that cost is almost nothing. But it can also refer to zero energy used during the building process or a net zero cost of delivering energy to the building site. It can even refer to net zero emissions produced by the energy used during building. If you're looking at buying or modifying a home to achieve net zero energy, most likely you're interested in how much money you can save over time. You also might be wondering whether net zero is just another marketing gimmick.
If data points make a difference to you, there are already over 14,000 net zero American building projects recognized by the Department of Energy's new DOE Zero Energy Ready Home program, formerly known as DOE's Building Challenge. The program establishes requirements for new build and retrofitted homes to qualify as net zero. Homes must be field-tested using the Home Energy Rating System (HERS) index and must meet at least the minimum standards to qualify as a true net zero home.
Embracing net zero energy homes: Get ready for change
Achieving net zero energy in a new-construction or retrofitted home depends on the successful integration of these two key elements:
- Extreme energy efficiency, especially where heat-retention in cold weather and cooling in summer are concerned. DOE Zero Energy Home program requirements include insulation that is compliant with IECC current codes; Energy Star-rated appliances, fixtures and windows, and compliance with Energy Star standards for homes.
- Home energy generated from renewable sources such as photovoltaic (PV) solar panels and geothermal heat pumps to accommodate a household's total energy needs.
It sounds straightforward enough, but until recently cost was a serious obstacle to making change happen. Federal government energy tax credits are still in place, however, through the end of 2016 for PV and geothermal home energy systems. The cost of these systems, especially solar, is dropping significantly, so homeowners have additional incentives to look at the long-term benefits of a home with little to no energy costs.
Not only is the cost of the systems lower; new construction costs to achieve net zero energy are falling, too. In an area where homes cost about $200/sq. ft., a new-build, three-bedroom, two-story net zero energy home in Seattle was finished a year ago for a final cost of $114/sq. ft. after rebates and incentives.
Builders in other energy-conscious states, like New Town Builders in Colorado, are also constructing net zero production homes priced competitively with other new homes in the same area. Their Zero Energy Now (ZEN) homes feature a PV system on the roof and a frame that forms an insulating "envelope" around the home. The homes have qualified for DOE Zero Energy Ready Home certification.
Currently, 39 states have emerging or verified zero net energy projects as reported by New Buildings Institute (NBI), which follows the latest developments in this area of green building advances. According to a study by the Net-Zero Energy Coalition, there are 146 organizations and 333 programs and other initiatives dedicated to promoting and advancing the attainment of net zero energy.
In addition to these efforts to encourage architects and builders to continue exceeding current energy conservation standards for buildings, local governments are modifying building codes to attain greater energy efficiency. The State of California has mandated Zero Net Energy (ZNE) for all residential buildings by 2020 and for commercial buildings by 2030. The new requirements will apply to certain retrofit projects as well. The Pacific Northwest region is creating an open source online data base to share innovative building plans that not only comply with new code requirements but also realize the goal of net zero energy.
At this stage in the green building movement, it appears as if cautious optimism is giving way to the true American spirit of innovation and competition. The California mandate hopes to provide impetus for investments in new technologies as well as confidence in high-performance building. Now it just remains to be seen whether home buyers are ready to fully embrace net zero energy homes.
Photo credit to Myryah Shea Irby