Net Positive Energy Is the New Net Zero
Buildings that produce more energy than they use suddenly are viable.
The era of the net-positive energy building is upon us.
Aided by lower solar costs, more energy-efficient building products and new tools that can better model energy use, cutting-edge architects and engineers are proving they can design a wide variety of structures in a wide range of climates that perform well beyond net zero.
Net zero energy buildings are those that produce as much renewable energy onsite as they use, as measured over the course of a year. Net positive buildings must produce at least 5 percent more renewable energy onsite than they use, also over the course of the year.
Much as net zero buildings moved over the last decade from pipedreams to increasingly common realities, net positive buildings are now moving past the proof-of-concept phase.
For certain building categories, such as skyscrapers and energy-intensive data centers, it’s still a stretch to provide more than enough electricity onsite. But the first three buildings below demonstrate that net positive is achievable on buildings that are a lot more substantial than a summer cottage. The fourth building, a proposed hotel above the Arctic Circle, hints that net positive can be achieved even under unlikely circumstances.
Burh Becc at Beacon Springs Farm
Completed in 2016, this 5,000-square-foot house and half-as-large workshop/garage sit on a 15-acre permaculture farm just outside Ann Arbor, Michigan. The buildings rely heavily on passive solar, including a south-facing “trombe wall” in the house to store heat for winter nights and a 37-foot cooling tower to pull hot air out during summer days. A geothermal loop provides radiant heat and hot water.
That leaves an astoundingly small demand for electricity, especially considering those cold Michigan winters. Sixty photovoltaic panels generated just over 20,000 kilowatt hours during the year the building was being audited for certification under the Living Building Challenge. Less than 80 percent of that electricity was used by the building, a fair amount of it to charge a Chevy Volt. The leftover energy was sold back to the local utility.
Brock Environmental Center
In 2001 the Chesapeake Bay Foundation completed the world’s first LEED Platinum Building, the Philip Merrill Environmental Center, in Annapolis, Maryland. A decade later, as the foundation settled on a site for a Virginia center, it was committed to staying on the leading edge of green building innovation.
The 10,000-square-foot Brock Environmental Center in Virginia Beach takes advantage of its windy, sunny location at the edge of a salt marsh by relying on solar panels and its own wind turbine. Site-specific design features reduce energy demand. For example, the building’s orientation and curved shape maximize natural light while limiting solar heat gain in the summer and increasing solar heat gain in the winter. It’s the kind of design detail enhanced by a new generation of powerful energy-planning tools. Cross-ventilating windows that are higher on one side of the building allow warm air to escape as it rises.
Over a 12-month-period, the Brock Center performed at an energy unit intensity of only 14.1 — among the lowest levels recorded for a modern, four-season building. The American Institute of Architects was so impressed that its Committee for the Environment last year gave the Brock Center its sole “Top Ten Plus” award for “exceptional post-occupancy performance.”
The Rocky Mountain Institute Innovation Center
The Innovation Center was intended not only to demonstrate efficiency but also to serve as a living laboratory for technology and design ideas advocated by the Rocky Mountain Institute (RMI), a leading research and advocacy organization on energy efficiency.
The owners were open to broadening the building’s designated “thermal comfort zone” so that lower temperatures would be considered acceptable. The thinking: When occupants get a bit chilly, they can put on a sweater. That flexibility cut down on the energy required for heating and lowered the HVAC expense.
According to a project description, the building relies heavily on its “envelope and orientation to maximize comfort without mechanical systems.” It helps that the 16,000-square-foot, two-story building is highly insulated, with R-67 insulation in the roof and quadruple-paned windows.
Various passive features, including operable windows, eliminate the need for air conditioning in summer and help to keep heat inside the building in the winter. Mechanical systems are minimal: A dedicated outside air system (DOAS) helps ventilate the air without losing heat, and electric radiant heat mats provide heat only on the very coldest days.
The result: An 83-kilowatt solar array is more than enough to power this large building perched 6,611 feet high in the Colorado Rockies.
Svart hasn’t been built yet, but the proposed hotel — a ring-shaped building that will rise on stilts from the water — will be among the most ambitious net positive projects thanks to its location. It will sit above the Arctic Circle in a Norwegian fjord, within view of the famed Svartisen glacier.
Oslo architectural firm Snøhetta claims the building’s orientation and design will reduce energy demand by 85 percent. Energy needs are projected to be more than met by rooftop solar panels and a geothermal system. The building will seek certification under a new European net positive standard called Powerhouse.
Ken Edelstein is editor of the Kendeda Living Building Chronicle, which covers green design and construction in the Southeast.
Top Image Credit: Beacon Springs Farm