A Green Building Grows In Cambridge
When biotechnology company, Genzyme, decided to build its headquarters in Cambridge, MA, the goal was to create a building that would be both aesthetically pleasing and environmentally responsible. Interior gardens, seating areas, and coffee bars provided the aesthetically pleasing aspect, while numerous environmental design strategies ensured the 334,000-sq-ft building would obtain the Platinum LEED® rating from the USGBC.
The 12-story Genzyme Center was completed in 2003 and features everything one would expect to find in a high-performance building, including energy efficient equipment, water-conserving appliances, sustainable materials, and outstanding IAQ.
Energy-efficient features, including fans, motors, and an extensive BAS, helped reduce the projected overall energy cost for the building by about 42%. A large portion of this energy savings can be attributed to the central heating and cooling systems, which are powered with steam from an adjacent power plant. The steam drives absorption chillers for cooling during the summer and is exchanged directly into heat during the winter.
This innovative heating and cooling system, along with state-of-the-art ventilation systems and individual temperature controls, has resulted in a comfortable, healthy environment for those working in - or just visiting - the Genzyme Center.
UP ON THE ROOFTOPThe Genzyme Center was a "frighteningly unique project for everybody involved," said Michael T. McGough, P.E., with Laszlo Bodak Engineer P.C., New York. McGough's firm was the engineer of record for the project and worked in association with Buro Happold Engineers, P.C. McGough noted that given the nature of this particular high-performance building, "the blending between engineering and architecture became blurred."
The German-based architectural firm, Behnisch, Behnisch, and Partner, designed the Genzyme Center, so European influences can be seen throughout the building. McGough stated he worked closely with the firm in order to understand their objectives and to "interface with the European mentality with regards to how building systems are put together and building services supported. In the U.S., we're more developer driven than Europe when it comes to our buildings."
That being said, the developer initially proposed a baseline packaged chiller system for the Genzyme Center, but that quickly changed. Instead, two 450-ton steam-driven absorption chillers were specified, with the steam being provided from a tertiary power generation cycle from the power plant next door.
This arrangement made perfect sense as steam lines are underutilized in the summer, and unused steam is often rejected. The steam used during the summer reduces electrical peak load demand and increases overall efficiency of the power plant.
The mechanical rooms sit at the top of the Genzyme Center, so infrastructure was needed to move the high-pressure steam from the power plant up to the chillers. Dual sets of pressure-reducing stations ensure the steam is at the design operating pressure before reaching the chillers. The hot steam condensate from the chillers is directed through a set of heat exchangers in order to preheat the building's domestic water before being pumped back to the power plant.
The chillers utilize a lithium bromide solution rather than any HFC refrigerant, and most of the chilled water pumps have VSDs. "For the chilled water we have a primary/secondary flow system, so the primary pumps are on/off, because the flow rate is constant through the chiller heat exchangers. The secondary pumps are variable speed to adjust the chilled water flow to the building as demand changes," said Terry McDonald, maintenance technician of the Genzyme Center.
The fan speeds on the induced draft cooling towers can be varied, allowing the towers to be ramped up in various stages. "We can have just water flowing through the towers with the fans off or on, or we can turn them on as variable speed to meet the setpoint needed from the towers," said McDonald. "In the winter, we can operate the building in a free cooling mode where we produce chilled water directly from the towers and turn off the chillers entirely."
A more recent change has been to dynamically reset the cooling tower setpoint based on chiller load. At night, the cooling load of the building decreases, so the cooling tower setpoint has been raised in order to allow the chillers to run more effectively. In the summer when temperatures increase, the setpoint is raised to within acceptable limits to minimize the energy consumption of the cooling tower fans. That, in turn, raises the steam use of the chillers a little bit, noted McDonald, but it is believed that more energy is saved using this strategy.
NO BOILERS TO BE FOUNDSteam provided by the power plant next door is also used for the four heat exchangers, which supply hot water to the fancoil and AHUs. Two small heat exchangers are used to produce domestic hot water.
The building uses four-pipe fancoil units with limited duct distribution serving interior zones, conference rooms, and perimeter zones. Separate fancoils are used for perimeters and the interior. A grand total of 560 fancoil units serve the Genzyme Center, and these units are automatically shut off when windows or doors are opened for natural ventilation.
Two 100% outside makeup air units located on the roof distribute ventilation air down through the building via two shafts, then a horizontal distribution is located at each floor to supply the ventilation air to the fancoil units. The two AHUs are 20,000 cfm each and can either be run in a pure heating or cooling mode to meet a temperature setpoint. They can also run in a humidity control mode, where the air is sub-cooled to remove the humidity and then reheated to the temperature setpoint. Heat wheels are located in each of the air handlers to recover energy from the exhaust air stream.
CO2 sensors are located throughout the building on a number of different floors, and if any of those sensors register above 1,000 ppm, the air handlers are signaled to bring in additional fresh air. "The supply air fan is on a variable-speed drive, and normally it's controlled to meet a static pressure setpoint in the air distribution ductwork. If CO2 levels are high, it will speed up to provide more fresh air, to try and bring them down," said Lou Capozzi, supervisor of facilities engineering at the Genzyme Center.
A large atrium space is located in the middle of the building, and radiant heating and trench heaters provide warmth for the atrium floor area in the winter. Trench heaters are a European product that are located in the floor and have a small fan that provides forced convection. "The trench heaters are for comfort as well as to keep the condensation off the glass," said McGough.
Given the size of the ground floor and its architecture, which includes water features, stairs, bathrooms, etc., it was not possible to obtain adequate capacity from the radiant floor heating system. The perimeter trench heaters supplement the radiant system, while providing the added benefit of blanketing the glass windows with heat.
KEEPING CONTROLAn integrated BAS from Tour Andover Controls (TAC) monitors and controls approximately 40,000 automation points in the building. Each point is programmed to respond to changes in the weather and in the interior environment, and to maximize natural light, bring in fresh air, and reduce reliance on conventional lighting and automated heating and air conditioning.
The BAS controls virtually every aspect of the Genzyme Center - from the water features to the chillers to the complex daylighting system. Every door and window along the perimeter of the building has contacts, so if someone opens a window, the BAS automatically isolates that office from the air conditioning system serving that zone. "That's one of the unique features of the BAS because we can actually turn off heating and cooling based upon somebody's desire," said McGough.
The lighting design provided the biggest challenge as far as the BAS was concerned, said Donna Thibodeau, project manager with TAC. "Basically, they wanted as much daylight in the building as possible while giving employees the ability to apply personal preferences to their space. So we gave the employees the ability to control the amount of light within their offices," said Thibodeau.
"They have the ability to brighten their rooms with artificial light; however, the control system will always return the lights to their original setpoints to conserve energy. It's not what we normally do in America. We usually turn on all the lights or else shut them off completely. We don't normally give the people to ability to control them," she added.
The BAS also monitors the roof-mounted heliostats, which are basically large mirrors that track the sun and redirect the daylight down into the core of the building. "The heliostats follow the sun as it goes around, directing the light to a stationary mirror. From the stationary mirror it goes down to a set of prismatic louvers that cover the whole atrium, reflecting sunlight through the whole building," said Capozzi.
The louvers also move with the sun's path and elevation and reflect glaring, direct sunlight back to the mirrors, allowing diffused light to enter the atrium. Once in the atrium, the light is further reflected to the floors by a system of hanging prismatic mobiles, reflective panels, and a reflective light wall on the inner surface of the atrium. On the outside glass walls, horizontal, reflective, motorized blinds reflect light up to reflective ceiling panels (the first two in the ceiling grid), which in turn reflect the light through glass inner walls deep into the floor plate.
McDonald noted that he has been most impressed with the level of detailed information he can obtain from the BAS. "The BAS gives us amazing alarm capabilities. For example, alarms will notify us when a fan belt might be loose and that will enable us to go and check it before it becomes a problem. In our computer rooms, we have chilled water Liebert units. If those get hot and our chillers are running, then the BAS alerts us that we have trouble somewhere in our chilled water loop, and we can go and look for the problem."
The BAS also monitors the fire control panels and the exhaust fans. From the BAS it's possible to trigger a test mode to ensure the fans are operational. When a fire alarm actually occurs, 78 fire doors are shut throughout the building and four 33,000-cfm exhaust fans start operating. The alarm is not run through the BAS, however, it's hard wired into the fire control system, noted Capozzi. "If a fire occurs, the atrium will actually become a chimney. The doors will open downstairs, and the fans will exhaust the air through the top."
The security system is separate from the BAS and primarily consists of card access to the building and more restrictive card access to sensitive areas or rooms in the building. There is CCTV monitoring, and the mechanical and electrical rooms are key access only.
As can be expected, it was not inexpensive to build the Genzyme Center. The project cost approximately $140,000,000, or about $400/sq ft. The total includes site preparation, including soil remediation, base building, tenant improvements, internal gardens, furniture, and fixtures.
The end result, though, is a Platinum LEED rating and a spectacular building that everyone enjoyed creating. "Ultimately, we were building something that hadn't necessarily been built before," said McGough. "It created a challenge for all the designers on the project - the architects, engineers, and the contractors. It was a truly unique and wonderful experience."
Side Bar: More Genzyme Center HighlightsThere are so many energy-efficient and/or unique features that were incorporated into the Genzyme Center that it's almost impossible to list them all. Here are a few other "green" details about the building.
Genzyme Center is built on the former site of a coal gasification plant, which had been abandoned after years of use, leaving a contaminated vacant lot in the heart of the Kendall Square community. The site was remediated, and Genzyme is proud to return it to productive use. The site is also located just two blocks from public transportation, encouraging employees to commute to work using environmentally friendly methods.
The building envelope is a high-performance curtain-wall glazing system with operable windows through all 12 stories. These windows are linked to the BAS, allowing for automated control and night cooling. Also, 32% of the exterior is ventilated double façade with a 4-ft interstitial space for circulation and occupation. These double-façade areas act as a buffer zone: in summer they block the solar gains and ventilate the heat away, and in the winter they capture heat gains, introduce it into the structure, and reduce thermal loss from the façade.
The building has two solar panel arrays on the roof of the mechanical penthouses, and the building has a vegetative roof that provides absorption and evaporation of rainwater.
Water conservation features include the installation of high-efficiency irrigation systems including soil and moisture sensors for both outdoor and indoor (garden) irrigation. Automated and low flow faucets, waterless urinals, and dual flush toilets installed in the building will reduce potable water usage by 32% below the standard established by the 1992 Energy Policy Act.