Every day, my inbox is flooded with stories of buildings that have gone through retrofits to save thousands or sometimes millions of dollars in annual energy costs. Despite being a no-brainer, energy efficiency, the lowest-hanging fruit in the energy garden, is still overlooked by many building owners, even though there are endless success stories.
And then there are zero-energy buildings (ZEB). Instead of changing light bulbs or going for LEED Platinum status, ZEB and their cousins, zero-energy-capable (ZEC) buildings, are pushing the envelope of what’s possible in the built environment.
With only 21 ZEBs and 39 ZEC buildings in the U.S., the concept is still orders of magnitudes away from even being an early trend. But a new report from the nonprofit New Buildings Institute about the lowest-carbon-emitting structures highlight some of the benefits that could be taken from these pilots and applied to the general building stock.
“With more examples of successful zero-energy-capable buildings,” the study authors wrote, “the benchmarking focus can shift to a forward-looking target of zero energy rather than comparison with the existing building stock.”
It is a little early to expect lawmakers to have benchmarking based around zero-energy buildings, since there are only a handful of states and cities that even have energy benchmarking rules on the books. Even more troubling, the Institute for Market Transformation estimates that only about 50 percent of buildings meet current energy building codes.
In a tight economy, there is also some political backlash over aggressive rules that would mandate zero-energy buildings in new construction. The United Kingdom had called for all new homes built after 2016 to be zero energy, but that was scaled back in 2011. The study found, however, that the added cost might not be as high as anticipated to get to an ultra-low-energy building. The typical increase in the buildings the study looked at found an added cost from 0 petrcent to 10 percent.
Many of the strategies used in constructing the buildings are also being used in the general building stock. Daylighting was the most popular design strategy, being used in more than 85 percent of the business cases. High-efficiency lighting and high-performance envelopes were also used in more than 60 percent of cases.
Of course, existing buildings, which will still make up the bulk of the stock even decades from now, can’t exactly get an entirely new envelope. But that doesn’t mean retrofits aren’t possible. One building in San Jose, the 6,560-square-foot IDeAs Z2 Design Facility, renovated a 1960s bank building by adding skylights, high-performance windows, increased insulation and a radiant heating and cooling system coupled with a ground-source heat pump.
Controls came into play to minimize plug loads, which represent a growing fraction of building energy use. Lighting controls were also used and phantom plug loads were turned off when the building was empty at night. “Net zero is not only a goal for nature centers and boutique buildings,” the study noted from this example, “but can be reached on a much broader scale.”
For buildings that aren’t considering deep retrofits, plug load controls and sensors will be an increasingly affordable way to drive some efficiency. Companies are responding to the market.
Computing giants like Microsoft have gotten into commercial building management, while lighting controls companies are going from just lights to whole building controls. PeoplePower and ThinkEco are looking to partner with original equipment manufacturers to embed controls in their products.
While the building controls big boys like Johnson Controls, Honeywell and Schneider Electric are pulling analytics into their controls, the majority of commercial buildings in the U.S. do not have a building management system, so solutions will be tailored for some of the medium and small buildings.
But getting to an average EUI (energy use intensity) of 30 kBtu/square foot is cheaper for smaller office buildings compared to large office buildings. (The national average EUI for all U.S. commercial buildings is 93 kBtu/sq. ft. When it comes to EUI, lower is better.) There is a premium of less than 7 percent in extra construction cost for buildings 50,000 square feet or less to achieve less than 30 kBtu/square foot.
The question of cost is a tricky one, as it can be difficult to quantify some design measures or choose the best “what would have been” scenario. For the IDeAs building, the company reported a 7 percent premium for energy efficiency-related upgrades, which came out to about $23 per square feet. There was another 2 percent cost increase for a 28-kW PV system after rebates and tax incentives.
For all of the examples, paybacks were 11 years or less, except for the PV system at the Aldo Leopold Center in Baraboo, WI (attributed to the low energy rates in that area). For most of the buildings, the cost of PV was one of, it not the single largest cost. As prices continue to dive for solar, the economics for pushing toward extremely efficient buildings make more sense.
The early examples of net-zero buildings could also help inform models and simulations that are being developed by the U.S. Department of Energy. “Right now, most of what’s done is absent of modeling done in most of the other major engineering industries,” said Henry Foley, executive director of the DOE’s Greater Philadelphia Innovation Cluster for Energy-Efficient Buildings. But even with all of the supercomputer modeling in the world, building use cannot be separated from the people who occupy it to achieve meaningful energy savings in a building of any size. “”It’s not just about technology,” said Foley. “It’s also about information and people.”