The City of St. Louis Park is on track to achieve Zero Energy certification from the International Living Future Institute for its HGA-designed Westwood Hills Nature Center, opening in June
By Joel Hoekstra
In 2018, after a group of high school students petitioned the city council to think more seriously about the impact of climate change on the community, the City of St. Louis Park adopted a climate action plan that would reduce greenhouse-gas emissions to net zero by 2040. To reach that goal, the community set ambitious targets that would gradually eliminate the use of fossil fuels—the leading cause of excess greenhouse gases—and boost the use of renewable energy sources. The city began replacing gas-powered vehicles and tools with electric ones and installed public charging stations at city hall and the recreation center. Electric accounts that were not powered with renewable energy were switched to Xcel Energy’s Windsource program.
Going forward, per the plan’s mandate, all new construction projects funded by the city would be zero-energy buildings (ZEBs)—meaning that each building’s energy use and production would be balanced (or result in excess power) on an annual basis. “We wanted to be looking toward the future and leading by example,” says Cindy Walsh, the city’s director of operations and recreation. “Even if that sometimes meant paying a premium, we wanted to invest in sustainability.”
This summer, the city’s first ZEB will open at the 160-acre Westwood Hills Nature Center, a former golf course purchased by the city more than 60 years ago and later converted into a nature preserve featuring marsh, woods, and restored prairie. The park’s new 13,000-square-foot environmental learning center—a replacement for a smaller, nondescript building that had served area hikers, birders, and schoolchildren since 1981—was designed to be both a teaching tool that connects visitors with nature and a model for zero-energy building construction.
Minneapolis-based HGA, the project’s architect, engineer, and landscape architect, leapt at the opportunity to work with a municipal client that was passionate about slowing the effects of climate change. “We’d never seen zero energy as a goal in an RFP from a municipality,” says lead designer Glenn Waguespack, AIA. What’s more, after some investigating, Waguespack realized the new learning center would be the first commercial ZEB—certified by the International Living Future Institute—open to the public in Minnesota. (A small building at the Science Museum of Minnesota is also net zero, but it’s not open to museum visitors.)
Maintaining a zero-energy balance requires almost daily management, adjusting thermostats and opening windows to reduce energy consumption. But building design also plays an important role. “The shape and massing of a building can have a huge impact on energy use,” says HGA principal Nancy Blankfard, AIA.
The new facility stretches east to west, with broad southern exposure. Long and narrow, with several large gathering spaces inside, the structure can be easily ventilated by opening windows. The overhangs of its butterfly roof are pitched to block the high summer sun but allow winter light to reach further into the building. A wall with high thermal mass collects heat from the sun on winter days and releases it slowly at night.
The HGA team employed several design strategies to reduce energy consumption. The structure has a tight envelope, with an R10 slab and R30 walls. (R-value measures a barrier’s ability to resist the conductive flow of heat.) Dual-element glazing cuts down on cold drafts in winter, while operable windows strategically placed to maximize air flow help keep indoor temperatures cool during the summer. Ceiling fans circulate air and regulate temperatures as well. On the technology front, electronic sensors measure interior daylight and adjust LED lighting accordingly. Importantly, the center highlights its programming without the use of large electronic displays or looping videos in its exhibits, both of which can be energy hogs.
Of course, operating a building still requires energy, so the City of St. Louis Park invested in rooftop solar panels. The photovoltaic arrays are set at an eight-degree, south-facing tilt to maximize summer and winter energy production. The building also utilizes a ground-source heat pump, with geothermal wells used as a heat exchanger.
(In addition to conserving energy, the building and landscape are designed to reduce water use. Low-flow water fixtures are expected to result in a 38-percent reduction in water use inside the facility, and the use of native plants eliminates the need for landscape irrigation.)
“We had a great experience with HGA,” says Walsh. “We believe the new building will not only be a community gathering place; it will also be a place where designers can learn about energy conservation.”
Estimates calculated by HGA suggest that a similarly sized building built to code and heated with an electric boiler would generate more than 130 tons of carbon emissions annually. The new nature center, if managed correctly, will generate zero.
“As our clients more fully understand how their choices impact energy and water use, architects will play a critical role in helping them envision and achieve a sustainable future,” says Waguespack.
WESTWOOD HILLS NATURE CENTER
Location: St. Louis Park, Minnesota
Client: The City of St. Louis Park Operations and Recreation Department
Architect and landscape architect: HGA
Zero-energy consultant: Integral Group
Exhibit designer: Split Rock Studios
Construction manager: RJM Construction
Size of interpretive center: 13,363 gross square feet
Scheduled to open: June 2020
ZERO ENERGY CERTIFICATION
To meet the International Living Future Institute’s Zero Energy Standard, projects must have 100 percent of their energy needs on a net annual basis supplied by onsite renewable energy. Certain exceptions are available in the form of offsets, but no combustion is allowed. Certification is based on a third-party audit of actual (as opposed to modeled) building performance.