In the early 1990s, Toyota assembled a special design team charged with developing an affordable “mean and green” vehicle that would have all the amenities of a modern car with the lowest emissions possible. By late 1997, the first-generation Prius hybrid car was available for sale in Japan.
Those first-generation Priuses were fuel-efficient but not perfect. But by proving that it was even possible to produce a hybrid car that people really liked, Toyota set in motion a critical chain of events that today is transforming the automotive industry. Reasonably priced, high-performing hybrids of all types are zooming into the mainstream. Looking ahead 10 years, we can imagine that new cars powered solely by fossil fuels will be in our rearview mirror.
With the U.S. Department of Energy reporting that buildings account for nearly 40 percent of our country’s carbon emissions, we need to trigger a similar transformation in our built environment. Despite the fact that people are beginning to understand the dire environmental consequences of not reducing our carbon footprint, architects haven’t begun designing mainstream, affordable, zero carbon buildings. The ones I’ve seen either have been too small to make a difference or too large and expensive to be relevant to our clients.
To better understand how we can put carbon neutral buildings within reach of our clients, a team led by HOK and energy and daylighting consultant The Weidt Group collaborated on the design of a Class A, zero emissions office building. Out of our 10-month effort emerged the 170,735-sq.-ft., Net Zero Co2urt, which we believe is a new prototype for reasonably priced, readily constructible, and marketable zero carbon emissions office buildings.
Location, Location, Location
The team selected an urban site in midtown St. Louis, Mo., for our project. We chose this site because the city has a distinct four-season climate, electricity costs in Missouri are among the country’s lowest, and more than 80 percent of the state’s electricity is generated by coal-fired plants—so the power is cheap and dirty.
Carbon neutral designs always will be location-specific. But we believed that if we could create an affordable design on this challenging site, then we could duplicate our process in almost any location.
Form Follows Performance
Net Zero Co2urt is a four-story office building with two 300-ft.-long office bars oriented on an east-west axis. The north and south facades feature optimum vision and daylight glazing that draws in light while maintaining a high-performance envelope. The east and west facades are essentially solid. The office bars are connected by two 60-ft.-long links that enclose an attractive courtyard. An adjacent two-level parking garage accommodates more than 400 cars.
Conserve, Then Generate
Generating energy is much more expensive than conserving it. We designed the building to be as energy efficient as possible before seeking to produce additional energy through on-site renewable sources. The design cuts the carbon emissions by 76 percent through energy efficiency, with minor additional first costs compared to a conventional LEED-certified office building. To get all the way to zero emissions, the design relies on 52,000 sq. ft. of photovoltaic panels spread across the roofs of the office bars and parking garage, as well as integrated into the south-facing shading devices. The solution includes 15,000 sq. ft. of solar thermal tubes on the southern facades.
Efficient HVAC System
With the architecture greatly reducing the HVAC loads, the team designed an ultra-efficient, in-slab, radiant heating and cooling system that is integrated with an underfloor air distribution system. As the radiant heating and cooling system provides temperature control, the air handling systems can be greatly downsized. Operable windows allow for seasonal natural ventilation. A raised floor offers flexibility for a multi-tenant layout.
Carbon Neutral Can’t Be Just Any Size or Shape
This scheme emerged from careful studies in which the architects worked closely with the energy and daylighting analysts and conducted extensive climate studies to establish strict performance parameters. The team’s mantra was, “model, measure, and manage.” We created a model of a virtual building, measured its performance at every step, and managed team members’ expectations until we designed a real building that works. Characteristics like the building massing, orientation, floor-to-floor height, window sizes, and quality of glass and landscaping all are optimized to ensure that the building can be illuminated without electricity during daylight hours.
Socially Significant and Inherently Beautiful
Architects can design affordable zero emissions commercial buildings now. Instead of designing whimsical structures with high-tech sustainable features tacked on, we need to create simpler, more humanistic buildings that fit into their neighborhoods while performing in a way our society so desperately needs. Our first-generation carbon neutral buildings will carry great social significance while being inherently beautiful.
Virtual Design Process
Except for two in-person project kickoff meetings, for which we purchased carbon offsets for air travel, the team avoided emissions by meeting virtually. We met for 15 intense design sessions — with many more smaller work sessions in-between — over a 10-month period ending in May 2010. Team members collaborated by using WebEx and HOK’s Advanced Collaboration Rooms, which allowed us to use high-resolution videoconferencing while drawing on virtual flipcharts.
Net Zero Co2urt Project Team
HOK: Architecture, engineering, sustainable design, landscape architecture, project management, cost estimating, Ecotect modeling. The Weidt Group: Energy and daylighting consultants. Green Street Properties/Michael Clark: Developer. Tarlton Construction: Construction cost estimating. Kozeny-Wagner: Construction cost estimating. The Biomimicry Guild: Biomimetic design.
Mythbusters for Zero Emissions Design
Our Net Zero Co2urt team found out that designing for carbon neutrality demands integrated, unflinching design and analysis, and that nothing is too important to be questioned or changed. Our science-based approach challenged the veracity of several long-held architectural beliefs:
Myth #1: All glass buildings are the future of low-energy and low-emissions design.
Although daylighting is the single-most important way to reduce electricity and carbon emissions, carbon neutral design requires a precise balance of light and heat. To determine the right combination of energy-efficient glazing and insulated wall panels, we modeled the daylighting savings offset by the energy penalty of increased floor-to-floor and glass area. These calculations told us how much glass we should use.
Myth #2: We can’t go wrong by planting trees.
We quickly discovered that placing trees in the wrong places would impede the daylighting solution. The landscaping must preserve access to natural light and be completely integrated with the building design.
Myth #3: Photovoltaic panels are effective only in bright, sunny, warm climates like California’s.
While our climate analysis showed that there are 150 to 180 cloudy days per year in St. Louis, there is more than enough sun to generate the required on-site solar power. We also learned that solar panels are more efficient in cooler climates—heat is their enemy.
Myth #4: We can’t design a zero emissions building to be higher than three stories.
We designed four floors. Admittedly, we needed to use the roof surface of the parking structure to house 17,000 sq. ft. of photovoltaic panels.
Myth #5: Zero emissions isn’t possible for a conventional project budget.
Detailed cost estimates calculated the construction cost to be $223 per sq. ft. Annual energy cost savings through energy efficiency and solar power will be $185,000.
The payback for the investment to reach carbon neutrality compared to our baseline building would be 12 years if the rise in fuel costs outpaces general inflation by 4 percent a year. The payback would be less than 10 years today in the many other areas of the United States where electricity is more expensive. Policy changes supporting low-carbon and low-energy initiatives, including additional federal and state incentives for renewable energy, could bring zero emissions buildings much closer to our grasp. Readers who believe reaching carbon neutrality is important can help by encouraging their local politicians to support more incentives and tax breaks for investment in renewable energy.
Click to read the Part One of this Green Essay with Ross Donaldson's "Woods Bagot and Buro Happold develop a model that delivers on the promise of zero carbon and zero emissions for large-scale development projects."