Zero-Energy Construction is ‘Set to Explode’
Zero-Energy Construction is ‘Set to Explode’
Ann Edminster’s keynote address at the Better Buildings By Design conference
California regulators have established an ambitious policy goal: Beginning in 2020, all new homes in the state must be designed for net-zero-energy operation. (GBAGreenBuildingAdvisor.com has published at least four news stories on California's net-zero target: here, here, here, and here.)
At the recent Better Buildings By Design conference in Burlington, Vermont, the keynote address was given by Ann Edminster, an architect, green building expert, GBA blogger, and board member of the Net Zero Energy Coalition. Her presentation, titled “Zero: The Cinderella of Energy Efficiency,” focused on the growing interest in net-zero-energy buildings.
Edminster lives and works in the San Francisco Bay area. She dates the beginnings of the net-zero-energy home movement to 2000, but her chronology is a little generous. Although researchers were indeed discussing the idea of net-zero-energy homes in 2000, no one had successfully built one until late 2006. Before then, all of the so-called “net-zero-energy homes” used more energy than they produced.
In a July 2004 article I wrote for Energy Design Update (“Getting Down to Zero”), I reported that most of the touted “net zero” homes of that era used natural gas, propane, or firewood to provide some of the home’s energy, making no attempt to offset these fuels with electricity production. Of the two all-electric homes that self-identified as “zero energy” homes in 2004, one had a PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. array that provided only 66% of the home’s electricity use, and the other had a PV array that provided only 20% of the home’s electricity use. At that time, the number of “zero-energy” homes that could demonstrate net-zero performance was zero.
In the pages of EDU, I announced a challenge. I promised to hail any builder, designer, or researcher who could provide 12 months of monitoring data showing that a PV-equipped single-family home qualified as a net-zero-energy home. It took until late 2006 for someone to come forward to claim the laurels. In the February 2007 issue of EDU, I announced the winner: a superinsulated home built in Wheat Ridge, Colorado, by the Metro Denver chapter of Habitat for Humanity was the country’s first net-zero-energy house.
2020 is almost upon us
Regardless of its actual starting point, the net-zero-energy movement has gained momentum quickly. Referring to the net-zero movement as a “Cinderella story,” Edminster told the audience at the Burlington conference, “Since Cinderella’s humble beginnings in 2000, the growth of net zero has been dramatic. … The number of net zero-energy projects is doubling every two years.”
Builders and developers in California are now beginning to realize that the 2020 deadline for adopting a net-zero approach to residential construction isn’t far away. “The construction industry in California is starting to look at [the mandate] in a different way now that 2020 is only three years away,” said Edminster. “Now they’re saying, ‘Tell us more.’ ”
Pay attention to five things
According to Edminster, “There is nothing exotic in the basic strategies used to attain zero energy.” She listed five aspects to the zero-energy approach:
- Efficient form and orientation.
- Right-sized mechanical equipment
- A renewable energy system (usually PV)
- A high-performance enclosure
- Best-in-class plug loads (lighting and appliances)
While this five-pronged approach hasn’t changed much over the last decade, Edminster sees changes on the horizon. “What we want starts to shift as we move these boundaries to include electric vehicles and battery storage,” she said.
[Photo credit: Efficiency Vermont]
HVAC contractors don't get it
Edminster provided a big-picture view. “Where is the zero energy movement now? First, it’s important to note that the movement is global,” she said. “There are examples in Japan, in South America, in Africa — all over. Second, the concept is being implemented at a community scale, as in Fort Collins, Colorado.”
She continued, “The early adopters were builders of custom and luxury homes. The second wave included builders of multifamily homes. The third wave includes spec builders and production builders. Meritage Homes claims to build more than 80 zero-energy homes each year. KB Homes has unveiled a zero energy prototype. Pulte is building a prototype.”
As most GBA readers know, choosing space heating and cooling equipment for high-performance homes can be tricky. “One technology need is low-load HVAC equipment,” said Edminster. “A zero-energy house in Stockton, California, only needs 6,000 BTUBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. /h of heat. So all available equipment is too large for low-load California homes. The HVAC design load is often 1,600 square feet per ton. The HVAC industry in California has no clue how to address low loads — the contractors want to install one ton for every 500 to 800 square feet.”
Embodied energy and embodied CO2
Edminster noted that for designers of zero-energy homes, “The forgotten stepchild is embodied CO2.” She noted, “Over the last three or four years, a few voices have begun to say that embodied energy matters for low-load buildings.” (Some of those voices have been heard on GBA; see, for example, All About Embodied Energy.)
“We need to consider the time value of the CO2 emissions associated with construction,” Edminister continued. “Embodied CO2 emissions happen when the building is built. It is a front-end load, and we need to be attentive to that front-end load. Maybe we need to build fewer new buildings. If we do build a new building, we should do it in the least carbon-intensive way possible. When it comes to embodied CO2, buildings get more energy-intensive as they go up. So let’s avoid high-rises.”
Bring builders and designers together
Edminster provided useful advice to designers and builders:
- “We need to focus on aesthetics. Some zero-energy buildings are not going to win any beauty pageants. We need to make sure that these buildings are attractive — buildings that people are going to love. Design matters!”
- “Make sure that you have a good team, with good coordination between the trades. Builders want a voice during the design. Constructability has to be factored in. Design and construction have to both be on board to get a zero-energy offspring. The right mindset requires commitment, creativity, experience, and engagement. Integrated designBuilding design in which different components of design, such as the building envelope, window placement and glazings, and mechanical systems are considered together. High-performance buildings and renovations can be created cost-effectively using integrated design, since higher costs one place can often be paid for through savings elsewhere, for example by improving the performance of the building envelope, the heating and cooling systems can be downsized, or even eliminated. and delivery improves performance without adding to the cost.”
- “When it comes to costs, we need to be asking the right question. The right question is, ‘What do we need to do differently to achieve zero energy without increasing costs?’”
- “To win over home buyers, sell the value, not the cost. A zero energy home is more than a home of the past, because it has a mini utility built in. Gene Myers, a builder in the Denver area, says, ‘I ask customers to give me $100 more per month, and I’ll give them back $300 in energy savings.’”
Her final words amounted to a pep talk: “The barriers to net zero are not technological; they are cultural and educational. This is a market opportunity. This field is going to explode.”
Martin Holladay’s previous blog: “Comparing Carpentry Tools to Surgical Tools.”
- Ann Edminster
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