Christopher Mims reports in the Wall Street Journal:
What if we could build structures that don’t draw any power from the grid, or use any natural gas, at all? And what if the materials and techniques required were no more expensive than conventional construction, or added at most a 10% premium to building costs? This is becoming a reality thanks to the Zero Energy Ready Home. These homes use so little energy that they’re “ready” to go net-zero—that is, what electricity they do need could theoretically be delivered with a roof full of solar panels.
Homes and commercial buildings consume 40% of all energy used in the U.S., according to the Department of Energy. What if we could build structures that don’t draw any power from the grid, or use any natural gas, at all? And what if the materials and techniques required were no more expensive than conventional construction, or added at most a 10% premium to building costs?
This is becoming a reality thanks to a nearly decade-old DOE standard: the Zero Energy Ready Home. These homes use so little energy that they’re “ready” to go net-zero—that is, what electricity they do need could theoretically be delivered with a roof full of solar panels, even if they’re connected to the grid. A related standard from Germany, called Passive House, leads to buildings so well insulated they demand very little outside energy for heating or cooling.
Because net-zero homes are sealed from the outside world, their interior environments are quieter, freer of pollution and more comfortable than conventional construction. That can make a big difference to health, especially in cities, where mounting evidence shows noise and air pollution affect early child development and cause chronic stress.
Energy savings from net-zero buildings in the U.S. are negligible today, but are increasing. As of 2017, 8,547 units of net-zero housing (powered entirely by solar panels) or zero-ready housing (still powered mainly from the grid) had already been built in the U.S., with an additional 38,863 in the construction, design or planning phases, according to the Net-Zero Energy Coalition, an industry group.
Growth is set to take off in 2020, when California will require all new homes be truly net-zero. (Commercial buildings have a deadline of 2030.) The European Union has set the same 2020 goal for every new building in Europe.
Granted, the number of new houses being built in the U.S. every year is around 1.2 million, so these structures still represent a fraction of construction in the U.S. And the much greater challenge is retrofitting the nearly 140 million units of existing U.S. housing. And while the materials to build these structures are now widely available, many are still new and unfamiliar to builders.
Price Drop
What makes zero-ready homes possible and even affordable are a handful of enabling technologies that have rapidly come down in price in the past decade, says Alisa Petersen, a senior associate at Rocky Mountain Institute, an energy and environmental think tank.
The first key technology is the “air source” heat pump. Conventional forced-air systems have an air conditioner and a separate heater, often fueled by natural gas. Heat pumps, which run on electricity, can heat and cool. Heating is accomplished by running the AC process in reverse: Instead of using a compressor to remove heat from inside a home, the heat pump moves outside heat into the home. Heat pumps have been common in warmer climates for decades, but they’re now radically more efficient, and can work all the way down to -10°F, says Ms. Petersen.
Rounding out the hyperefficient home are heat-pump water heaters, which operate on the same principle; LED lighting, which can use as little as a tenth of the electricity of incandescent bulbs; and major appliances such as clothes washers that use less than a third of the power they demanded 25 years ago.
Zero-ready structures are also designed to lose less energy. That means sealing them against drafts and insulating them so very little heat leaks through their walls, windows and doors. But a sealed building can create stale air, humidity and mold issues, hence the need for an energy recovery system. This lets the structure breathe, and exchanges heat between incoming and outflowing air.
Breaking Ground
The Passive House standard—which focuses on low-energy heating and cooling, and relies on many of the same technologies—is gaining popularity in dense cities and multifamily buildings. The world’s tallest Passive House building, a housing tower on Cornell University’s new tech campus on Roosevelt Island in New York City, was completed in 2017.
Building a 26-story structure to the Passive House standard required the collaboration of around a hundred engineers, scientists and structural engineers—plus the contractor, says Deborah Moelis, a founding member of Handel Architects and the lead on the project. An unbroken envelope of insulation and vapor barriers from its bottom floor to the top keeps the building air tight. This is nearly unheard-of in conventional construction, where slabs and columns often interrupt a building’s insulation layer.
The end result is a building that uses a third as much power as a conventional new building would. Even if the power goes out, it should stay warm for a long time, says Ms. Moelis. Her firm is currently working on large Passive House buildings in Boston and New York’s Harlem neighborhood.
David Resnick, a real-estate developer for more than 40 years, was once among the skeptics of zero-ready construction. “My motivation is to make money,” says Mr. Resnick, who acknowledges he mostly ignored green building standards for the bulk of his career. But meeting with Rocky Mountain Institute analysts convinced him the cost premium on zero-ready homes was small.
He tapped Rod Stambaugh, founder of Sprout Tiny Homes , a builder of unconventional, even mobile, residences, who had constructed zero-ready cabins for a ski resort in Aspen, Colo. Sprout already had a 45,000-square-foot manufacturing facility in Pueblo, Colo., near a development Mr. Resnick was planning. The result: 750 planned zero-ready homes ranging in size from 1,100 to 2,500 square feet, with high-performance features like heated flooring.
Building new zero-ready housing is relatively easy, compared to retrofitting buildings. Sam Bargetz, co-founder of Brooklyn, N.Y.-based architecture firm Loadingdock5, says that when his firm renovates an existing building to meet the Passive House standard, it can cost almost as much as a totally new building. In New York, there’s still interest, because gut renovation is already so costly.Outside of areas with the highest incomes and property values, the best chance of improvement will be the creeping adoption of many technologies used in the net-zero standard, from heat pumps to multipane windows. “Costs are changing quickly,” says Ms. Petersen. “You don’t have to throw every efficiency measure at a home to make it net-zero.”
For those with the means to build, however, zero-ready homes provide newfound luxury as well as efficiency. “It’s much quieter than a regular building, and it’s dust-free,” says Mr. Bargetz.
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