An integrated design team, led by HOK and energy and daylighting consultant Minnetonka, Minn.-based The Weidt Group, has determined it is possible to construct a market-rate net zero emissions Class-A commercial office building in today’s market as a result of a 10-month virtual design exercise.
The team selected a potentially developable site in midtown St. Louis for the Net Zero Co2urt project. They selected this site for its challenging four-season climate, because electricity costs in Missouri are among the lowest in the country — a factor that challenged the team’s ability to make the design affordable — and because St. Louis’ electrical fuel profile is 81 percent coal. The team determined that the focus would be on net zero emissions, not energy, since buildings are responsible for 39 percent of the carbon dioxide emissions in the United States.
“We believed that if we could create a carbon neutral design for this difficult site, we would be able replicate our process in any other location,” says The Weidt Group principal David Eijadi. To help achieve that goal, the team is sharing a detailed explanation of the design solution and a replicable net zero process at netzerocourt.com.
Design of the 170,735-square-foot speculative office building features two 300-foot-long office structures that are positioned east-west and connected by two 60-foot links that enclose an attractive courtyard for the enjoyment of building tenants.
The integrated design of Net Zero Co2urt reduced carbon emissions by 76 percent through energy efficiency strategies, with only minor additional first costs compared to a conventional office building. To provide the remaining clean energy required to reach zero carbon emissions, the team identified on-site renewable energy systems that include approximately 51,800 square feet of rooftop and wall-mounted photovoltaic panels and 15,000 square feet of solar thermal tubes.
Detailed cost estimates illustrate that with an estimated construction cost of $223 per square foot, this project is marketable and affordable now. Annual energy cost savings through the building’s energy efficiency, solar thermal and photovoltaic system are $184,567, leaving an annual energy cost of $2,418, or 1 cent per square foot at current utility rates.
Payback for the investment required to reach carbon neutrality compared to a LEED® certified baseline building would be 12 years if the rise in the cost of fuel outpaced general inflation by 4 percent a year. But the payback would be less than 10 years today in the many other areas of the country where electricity is more expensive.
“The exciting part is that we can do this now,” says Mary Ann Lazarus, firmwide director of sustainable design at HOK. “The challenge for architects is to embrace the limitations presented by daylighting and energy analyses. By developing innovative design solutions within these strict performance parameters, we can create truly extraordinary zero emissions buildings.”
“This project was analogous to designing a first-generation Prius,” adds HOK chairman Bill Valentine, who helped lead the design team. “It’s not perfect but it’s an incredibly important start. All of us in the design profession need to push carbon neutral design into the mainstream as quickly as possible.”
The innovative design of Net Zero Co2urt will be showcased at HOK’s booth at Greenbuild 2010 in Chicago from Nov. 17-19. HOK will exhibit at booth #1122.
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