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Kroon Hall, Yale University’s School of Forestry & Environmental Studies building on Science Hill, is ultra-green. Designed by Hopkins Architects and Planners, Kroon Hall incorporates a wide range of sustainable strategies and design features. Coolest feature according to Solaripedia: the large bank of photovoltaics on the south face of the arched roof, supplying about 25 percent of the building's power. Kroon Hall was built on a pre-developed site, following the campus masterplan to develop Yale’s Science Hill and the large open space surrounding the building. The site materials, such as light-colored concrete and the south courtyard’s green roof, were chosen to combat the urban heat island effect. The building potable water usage is estimated to be reduced 81 percent below that of a comparable building. Stormwater is collected from the roof and grounds, then filtered through native aquatic plants. Wastewater (graywater) is collected from sinks and showers, then combined with the stormwater and used for all non-potable needs such as toilet flushing and irrigation. Water demand is further reduced by the installation of low-flow plumbing and irrigation fixtures.
Quick Look at the Sustainable/Climate Neutral Features
• Demolition and construction waste is being recycled
• Geothermal benefit from the underground placement of the north side of the lowest level
• Solar heat gain in winter and natural lighting year round along the long unobstructed south-facing wall
• Rooftop solar panels and solar water heaters
• Geothermal energy system
• Natural light and ventilation
• Natural light will be augmented with artificial light to maintain a constant lighting level; the latter is also controlled by sensors that shut off automatically if no one is present
• Manually operable windows utilize natural air circulation
• Green construction materials including “thermally inactive” concrete and low-E glass and insulation, waterless urinals and low-impact paint
• Recycled, recyclable, sustainably harvested or manufactured nontoxic materials
• Sustainably harvested wood
• Exterior stone quarried within 500 miles of campus
• Rainwater harvesting system and cleansing pond
Kroon Hall uses 58 percent less energy than a comparable building of a similar size and program. The building achieves good energy efficiency through passive design, optimized lighting and incorporation of renewable energy sources on-site, including photovoltaics and solar hot water.
The east-west orientation of the building takes advantage of solar access and natural ventilation. The building envelope is highly insulated and a green roof serves as a courtyard and covers a service lot and storage rooms below. Fresh air ventilation and free cooling cycles on air handling units reduce the need for air conditioning most of the year. Indicator lights alert occupants when conditions are suitable for opening windows. Concrete walls and exposed concrete ceilings retain heat in winter and help cool in the summer.
When air conditioning is necessary, displacement ventilation and indirect evaporative cooling condition the spaces using 75% less energy than a typical building. In winter, the heat recovery system warms the air using available energy first from the occupants, lights and appliances, which is then supplemented by geothermal energy. High efficiency electric lighting and controls further reduce energy use and the cooling load. All appliances and equipment are Energy Star-rated.
To offset some of the energy required by the already energy-efficient Kroon Hall, solar energy is generated on the site. Solar hot water is used to heat at least 50 percent of potable water. The photovoltaic array on the roof, which was funded in part by the Connecticut Clean Energy Fund, provides approximately 25 percent of the building’s electricity. The all-electric building’s design eliminates all on-site combustion. The ground source heat pumps serve as the building’s heating and cooling plant and utilize only HFC refrigerants.
Almost 80 percent of the timber purchased for the building is FSC-Certified, and the building has 16 percent of the materials with recycled content and 34 percent from regional sources. Kroon Hall also focuses on improved indoor environmental q, maximizing daylight and views to the outdoors, and use of high-efficiency filtration for ventilation air. Occupants also have control of their visual and thermal environment, and inhabit spaces where the air has low concentrations of volatile organic compounds.
Kroon Hall Rainwater Harvesting System
By Alan Bisbort 2007 Yale magazine -
When ground was broken on May 3, 2007 for Kroon Hall, Edward Bass – a major donor whose generosity helped make the school’s landmark building a reality – pointed skyward and said, “We can only go up from here.”
Bass’ enthusiasm notwithstanding, the architects and engineers had other ideas. Indeed, in order to meet the specifications for a Leadership in Energy and Environmental Design (LEED) -certified platinum building, the construction team had to go down from there – as in underground.
To qualify for a platinum rating – the highest set by the U. S. Green Building Council – Kroon Hall must produce nearly as much energy as it consumes through features such as solar panels, solar water heaters, natural light and ventilation.
Of the underground features, the most exciting may be a rainwater harvesting system that will provide water for flushing toilets, as well as for irrigating the native fauna in the two courtyards on the 3.5-acre site. And, thanks to a recent $1.5 million donation from the Mars family, this feature will be made possible.
“The rainwater harvesting system will conserve water, contribute to better water quality and control the rate of runoff during a storm by detaining and slowly releasing excess stormwater,” said Nicole Holmes, the project manager for Boston-based Nitsch Engineering. “That will be beneficial to the city and the environment, because the school will be drawing less water from the city’s aquifer and not be using any drinking water for irrigation or toilets.”
“This system will pay for itself, with savings from the potable water that would have been used, within ten years or so,” says Holmes. The rainwater harvesting system, collaboratively designed by Nitsch Engineering, Philadelphia-based Olin Partnership and Arup, an engineering firm with offices in the United States and Europe, will allow all rainwater that falls on Kroon Hall’s roof and grounds to enter into a 24-hour-a-day recycling process that will take place in a pond and subterranean tanks. Together, Nitsch and Olin transformed the current patchwork of above-ground service roads into “watering holes,” figuratively and literally – gathering places for students, as well as for the reuse of harvested rainwater.
The rainwater harvesting system is expected to save approximately 500,000 gallons of potable water annually, and will satisfy at least six LEED credits, including two points for stormwater management and four points for water efficiency. LEED platinum buildings must achieve 52 to 69 credit points.
“The biggest challenge was the steep terrain of the site, with its 20-foot slope from north to south,” said Holmes. “We had to look to the lower [south] end of the site for the treatment aspect of the rainwater collection system. However, the south side of the site sits just above an underground service node. For treating water, this allows very little ground space within which to work.”
Holmes said the goal will be to get the dirty water treated quickly. “The dirtiest portion of storm-generated water is the first inch that runs off of impervious surfaces. To catch this, we had to have a diversion structure upstream, at the north end. All of the water that falls on the northern part of the site and through the rooftop drainage system goes through this diversion system.”
The diversion system will consist of an underground manhole-type structure that will pipe the first inch of stormwater to a pond created by Olin that will feature specially selected aquatic plants, such as iris, cattails, arrowheads and lotuses, serving as biofilters to clean the water.
“We first thought that the best way to clean the water was to pull it through soil,” said Cricket Brien, an Olin associate. “But we had only one foot of space above the service node to work with. We had to think of another way. We consulted pond scientists who had devised rafts of plants specifically designed to clean water. We discovered that mats of trailing roots in a pond are more effective at cleaning runoff water than soil. They not only take the nitrogen and phosphates out of the water, they trap fine particles, too.”
Any flows greater than an inch will be carried by a separate pipe to a 20,000-gallon fiberglass-reinforced underground harvesting tank, which will also collect overflow from the pond and rainwater from the Kroon Hall roof. That mix will then be circulated through the pond for additional cleansing. The water stored in the harvesting tank will also be used for landscape irrigation and be diverted to a separate 940-gallon “day” tank located in Kroon Hall’s basement, where it will be filtered and disinfected for use in toilets. A hookup to a city line will provide water for drinking and washing.
“Part of what is unique about this project is that Yale, as an institution, has looked at the long-range impact,” said Holmes. “This system will pay for itself, with savings from the potable water that would have been used, within 10 years or so.”
Kroon Hall Floor Plans (779 kb)