HOK Challenges Designers to Target Net-Zero Energy
From concentrated photovoltaics in Southern California to adaptable building skin in Missouri, HOK’s teams explored a wide range of innovative net-zero energy design strategies in a recent internal competition.
“Our goal for this design competition was to encourage our people to pursue systematic and interdisciplinary solutions for achieving net-zero building design,” said Anica Landreneau, Associate AIA, LEED® AP, BD+C, HOK’s director of sustainable consulting. “It’s critical that we do this to help our clients address today’s energy and climate challenges.”
New technologies and design strategies are making the idea of designing net-zero energy buildings, which produce as much on-site renewable energy as they consume over a year, more mainstream and commercially viable.
The competition challenged HOK’s teams to create a conceptual net-zero energy design for a building on a site in their local communities. Specific urban infill sites were pre-selected in the 23 cities that HOK has offices. Entrants were given four potential programs – medical office building, residential, commercial office building and academic building – with the ability to add retail and mixed-use components.
Teams were required to use HOK’s Sustainable Analysis Tool to obtain climate data, set energy use intensity (EUI) targets and estimate the size of on-site renewable energy systems required to reach net-zero energy.
Members of HOK’s global design board served as the jury. The group evaluated each entry based on the team’s use of the Sustainable Analysis Tool; achievement of net zero energy; site design (including parking); form and massing; envelope design; daylighting; engineering solutions; behavioral strategies; renewable energy strategy; aesthetics/beauty; and innovation.
“The four winning projects represent truly integrated design solutions,” said Landreneau. “More than just building forms and systems, they include original designs for envelope and shading components that collect stormwater and solar energy while protecting the buildings from solar heat gain.”
1st Place: SoLAr
Los Angeles, California
The design for this mixed-use residential, commercial, and retail project maximizes the energy output from photovoltaics integrated into the structure.
Inspired by the large, commercial installations scattered across the Mojave Desert, the team chose concentrated photovoltaic (CPV) systems that require a smaller PV area while providing efficiency levels of up to 40 percent. Heat generated by the CPV system can be used for solar water heating and geothermal heating/cooling. Because Southern California is rich in sunshine but poor in water resources, the secondary focus on this design is on water use and reuse.
HOK team: Jessica Ginther, Frank Cauthen, Jamila Valero, Zach Capehart, Kris Surichamorn
2nd Place: Open Source Closed Loop
St. Louis, Missouri
This small office building in St. Louis achieves net-zero energy use through several strategies focused on modal specificity and systematic adaptability.
Integrating the systems minimizes energy loads and produces renewable energy. An adaptable boundary layer manages heat transfer, acting much like human skin. In warmer conditions, the skin relaxes and expands its surface area, triggering more convective heat loss. In cooler temperatures, the skin tightens or “bristles,” creating a thermal buffer to minimize heat loss.
HOK team: Jonathan Murphy
3rd Place: Feedback Hydronics
St. Louis, Missouri
Through research, testing and consultation with local engineers, the team developed a fully integrated hydronic heating and cooling system for a St. Louis culinary school and restaurant.
The system allows for feedback and self-correction while it adjusts its operations according to differences between actual and desired output. A fully integrated solar thermal skin and structure are embedded with the hydronic closed-loop system to minimize loss and maximize gain. Secondary systems include a subterranean labyrinth, an anaerobic digester and an electronic chiller.
HOK team: Brian Ballok, Leslie Wheeler, Christoph Ibele, Brad Liebman, Lauren Field
Honorable Mention: D-Breath
The design goal for this Beijing medical office building was to address the city’s massive air pollution problem.
An intelligent, charcoal-brick framework and infill system incorporate smart modules that are based on optimal orientations for sun and wind. Solar heat is harvested for energy exchange and natural ventilation strategies are fully integrated into the structure and envelope. D-breath, which features an infill system tailored to the specific geographic location to maximize the performance, can be located anywhere in the world.
HOK team: Philip Kwong, Yuhai Cheng, Xiaoqian Yang, Summer Su
The Next Frontier
Though these entries are conceptual, HOK’s teams will continue to collaborate on interdisciplinary thinking to push for innovative net-zero energy design that improves the performance of our built environment.
Current HOK projects with net-zero energy goals include the San Francisco Museum at the Mint, the Golden Empire Transit Central Facility in Bakersfield, Calif., the William Jefferson Clinton Children’s Center in Port-au-Prince, Haiti, and the Byron G. Rogers Federal Office Building and US Courthouse in downtown Denver.