Detail: photovoltaic roof of the Kendeda Building for Innovative Sustainable Design, Atlanta
Jonathan Hillyer

Detail: photovoltaic roof of the Kendeda Building for Innovative Sustainable Design, Atlanta

15 Jan 2024  •  詳細  •  By Collin Anderson

The Kendeda Building for Innovative Sustainable Design at the Georgia Institute of Technology is crowned with a lightweight canopy of over 900 photovoltaic panels. The roof generates all of the building's electricity needs and captures rainwater for drinking and site irrigation. It extends far beyond the main building volume to cast shade on its facades and create an outdoor space large enough to accommodate classrooms and other social activities for the university campus. The canopy is so effective at reducing the building energy loads that the design team refers to the building as 'shade-powered'.

photo_credit Jonathan Hillyer
Jonathan Hillyer

Photovoltaics have been applied to buildings for nearly half a century, with the purpose of generating renewable energy and curtailing reliance on the grid. The performance and aesthetics of photovoltaic cells and panels have slowly improved over the decades to yield products that are more financially interesting and visually attractive. Today's widespread acceptance of rating systems measuring the impact of buildings on their natural environments has, in many cases, made the implementation of photovoltaics an imperative to receiving certification. Institutional buildings funded by donations or endowments in particular have been at the forefront of such certification exercises. 

Even as the efficiency of photovoltaics has improved, the sheer surface area of ​​​​panels required to make them effective means that they are still typically a defining architectural element of the buildings they support. This is certainly the case for the Kendeda Building, located on a university campus just north of downtown Atlanta. Seattle-based The Miller Hull Partnership designed the building's 18,000 square foot (1700 square meter) roof in collaboration with local firm Lord Aeck Sargent to absorb the unrelenting Georgia sunshine and transform it into enough electricity to power well over 100 percent of the building's energy needs. The roof also doubles as a funnel for rainwater which empties into an underground cistern used to, among other things, irrigate the site's green landscape designed by Andropogon Associates

The 47,000 square foot (4,400 square meter) Kendeda Building has garnered certifications for LEED Platinum as well as the particularly demanding Living Building Challenge. It is the first building to receive such a rating in the Southeast United States, where a warm and humid climate poses particular challenges for renewable energy and passive design. The building program consists of two 64-person classrooms, four class laboratories, a conference room, offices, a makerspace and an auditorium.

photo_credit The Miller Hull Partnership
The Miller Hull Partnership
photo_credit The Miller Hull Partnership
The Miller Hull Partnership

 

Designing a 'radically sustainable' building in Atlanta

Financing for the building came in part from the Atlanta-based Kendeda Fund, a private organization which supports green projects that benefit their communities and teach users about sustainable consumption. To meet the aspirations of the Kendeda Fund, the building for Georgia Tech was designed in the spirit of meeting the stringent Living Building Challenge requirements. 

Living Building Challenge-certified projects need to be both socially engaging and energy independent. The certification requires that buildings are regenerative and connect occupants to agriculture, to nature and to their communities. It also demands that they are self-sufficient, remain within the resource limits of their sites, and positively impact the users who interact with them. 

The Miller Hull Partnership has a portfolio of environmentally-friendly public and institutional buildings that was attractive to the donors from the Kendeda Fund. The studio's projects range from the much-visited Pike Place MarketFront in downtown Seattle to the Health Sciences Education Building for the University of Washington. But its work is located primarily in the cool region of the Pacific Northwest, and it was clear from the outset that the design team would be operating in unfamiliar conditions in subtropical Atlanta. “Seattle has such a benign climate, it never gets very hot, it never gets very cold,” says Matt Kikosicki, an Architectural Designer at The Miller Hull Partnership. “In the foothills of the Appalachian Mountains, Atlanta gets cold winters and incredibly hot, humid summers. We knew that it was going to be a challenge to make a comfortable building.” The firm teamed up with the Atlanta studio of Lord Aeck Sargent to better understand what it means to build effectively in such heat.

photo_credit The Miller Hull Partnership
The Miller Hull Partnership
photo_credit Gregg Willett
Gregg Willett

One of the imperatives of the Living Building Challenge is that of long-term positive energy generation. Photovoltaics immediately became integral to the design concept. “It was the best renewable option in the region and on this site,” says Kikosicki. “There are other ways to solve for renewables, but one of the most readily available ways is with solar-electric generation. At the same time, the photovoltaic area that we needed would be so large, that it would clearly become the calling card of the building, so to speak.”

To take advantage of the large number of photovoltaics his studio wanted to use them in more ways than one: “As architects, when we think that something is fixed or likely to happen, we try to understand how we can leverage it to make it important to the design of the project. We are always looking for simple concepts or simple notions that we can layer onto.” The design team considered the ways in which people have dealt with the hot Atlanta climate for centuries and quickly latched onto the notion of the simple regional architectural device of the front porch. “The southern porch is a kind of social space, a third place neither inside nor outside the building where people meet and where one can watch the world go by,” he says. An outdoor covered space that functioned like a large-scale porch became something that resonated with both the architects and the client.

photo_credit The Miller Hull Partnership
The Miller Hull Partnership
photo_credit Gregg Willett
Gregg Willett

Kikosicki also notes that, to meet the demands of the Living Building Project, a building requires many systems that accumulate to become rather expensive: the more that systems can overlap or lean on each other to serve multiple purposes, the more economical. The architects studied the positioning of the large surface area of ​​​​photovoltaics as a canopy to create shade and reduce solar loads and consequently cooling energy demands. “It's like a giant umbrella that cools the building and the site around the building,” he says, referring to the canopy. “It’s also a rainwater collection system and a civic identifier.” Kikosicki likes to say that the building is 'shade-powered' due to the fact that its canopy mitigates the climate while providing all the needed energy for the building.

 

Detailing the canopy

The canopy is designed as a lightweight armature set on and around the main building volume. It has a structural frame of high-performance coated tube steel and is set on slender columns, two stories in height, that are braced with tension rods to give the system a delicate, intricate aesthetic like that of lacework. The structural grid of the building is set at 10.5 feet (3 meters) which loosely corresponds to a typical laboratory planning module, should the university wish to convert interior spaces in the future. 

The columns support two layers of rectangular HSS beams onto which are set eight bands of photovoltaic panels attached by vertical brackets. The photovoltaic bands are parallel, organized in the east-west direction and pitched at five degrees towards the south to balance optimal sun capture with the ability to collect and shed rainwater. The entire structural system is painted white to appear luminous and lightweight.   

photo_credit Jonathan Hillyer
Jonathan Hillyer
photo_credit The Miller Hull Partnership
The Miller Hull Partnership

One of the challenges that the architects faced was how to connect the photovoltaic panels at the seams and make a water-tight surface that could efficiently channel water. Waterproof taping is a typical application for such a system but it does not work with all the panel types here. The design instead adopted a backer rod placed within panel joints and topped with a stable sealant. At the low end of each photovoltaic band, a stainless steel gutter catches rainwater that flows off the panels and directs it into drains within the main roof of the building. The water then makes its way to a 50,000 gallon cistern below the public zone of the ground floor. The catchment area of ​​the roof collects enough rainwater to support 100 percent of the building's drinking, washing, showering, lab uses and composting toilets. It is estimated that the building harvests 460,000 gallons of water a year, approximately 41% of the annual rainfall on the site. The design team reviewed 30 years of weather data to size the cistern with enough water to overcome historical droughts. 

In order to control costs, the photovoltaic product would not be known until the end of the project; and so while the dimensions of the overall system were set, the design of the photovoltaic bands would need to be flexible enough to accommodate any potential type of cell. The final product implemented was manufactured nearby in Georgia. It is exposed on the underside and its size works well with the building grid. The solar array is designed to generate some 455,000 kWh of electricity per year to serve the building's demands for lighting, heating and cooling, water systems and plug loads. It is estimated that the building supplies 225 percent of its energy needs on an annual basis; the electricity generated beyond what the building uses to adjacent buildings for their use. When the roof is not producing adequate amounts of electricity, the building loads run off of electricity from the grid. 

photo_credit The Miller Hull Partnership
The Miller Hull Partnership

The canopy is set at 40 feet (12 meters) above grade and extends the same dimension beyond the west facade of the building. The overhang is designed to provide sufficient shade on the facade and protect it from the strong western sun for much of the year. It also creates a generous shaded outdoor space much like a porch. “The space below the canopy and around the building feels like the right scale for the campus,” says Kikosicki, where a tiered pedestrian zone is fitted with wooden benches used for outdoor classes and socializing. The photovoltaic panels are translucent and diffuse some sunlight; this as well as openings within the canopy allow for the transmission of ample northern light and views to the sky. 

Within the building the industrial aesthetic of the roof is continued. A timber structure in glulam columns and beams is reinforced with tension members to support spans of up to 40 feet (12 meters) in a central atrium and auditorium. The second-level decking is made of nail laminated timber that alternates between 2 x 4 and 2 x 6 members. According to Kikosicki these decks were designed to reduce the amount of material used, and to produce a texture that is visually interesting and lends some acoustic performance.

photo_credit Gregg Willett
Gregg Willett

 

Achieving net-zero: salvaged materials and reduced loads

For a building to possibly achieve net-zero carbon emissions, the first step in the design process is to reduce overall energy demands by, for instance, finding ways to lower electric lighting loads and specifying an efficient envelope. Once the load is reduced, the remaining energy demand will need to be accommodated by technologies like photovoltaics and other supplementary systems. The building also needs to continue operating yearly on a net-positive basis. 

According to Kikosicki the rough area of ​​photovoltaics needed to offset the energy demands for the Kendeda building was generally in line with the size of the site. Exterior motorized blinds additionally help to reduce solar gain on the envelope. Within the building operable clerestory windows at the roof provide daylight and natural ventilation, an effective passive design technique for reducing the need for electrically-powered artificial lighting and air conditioning. A total of 63 ceiling fans throughout the building also circulate air and are controlled by motion sensors that allow for automatic shut-off.

By eliminating 99 percent of construction waste and incorporating materials salvaged from other campus buildings, such as slate roof tiles used as bathroom tiles, the project diverted more waste than it created. The material also came from sources outside the campus: “Television filming is popular in Atlanta these days and there are plenty of stage sets built from 2 x 4s that are then discarded,” says Kikosicki. This otherwise discarded film set timber was incorporated into the building decking. 

Other design elements helped the building to achieve Living Building Challenge standards. A rooftop garden of 5,000 square feet (460 square meters) hosts a honey bee apiary, a pollinator garden, a blueberry orchard and a laboratory, satisfying an agricultural requirement while also creating a unique academic research space. 

photo_credit Gregg Willett
Gregg Willett