What works to cut data centre energy usage

The newest green data centres share many features: They're built using locally supplied and recycled materials; waste is minimized during construction; lots of windows provide extensive natural lighting; and fluorescent lighting with dimmers is used throughout.

These buildings have occupancy sensors so that lights and temperature automatically adjust when no one is in the room. Another common feature is raised flooring with under-floor heating and cooling used throughout the buildings, not just in the computer rooms.

The EPA's National Computer Center (NCC) at Research Triangle Park, N.C. -- a 95,322 square foot, 200-employee facility -- is a LEED Silver building. To get that certification, architects rotated the building so that the offices and lobby face south to allow the sun to help heat the building.

"The current orientation does take advantage of the sun, but in the summer that adds to the heat load," says James White, a physical scientist with EPA's Office of Administration Resources Management at Research Triangle Park. "One of the things we learned from this is to focus on really good glass glazing for the windows. This keeps your lighting factor up but reduces the heat load."

Architects also cut the size of the building by 20 per cent from its original footprint, and designed in the capability to expand it later rather than building in extra capacity.

"One of the big buzzwords is rightsizing," White says. "You need to really focus on sizing the building correctly and balancing loads so you don't build in unnecessary energy systems."

NCC's most innovative feature is the special solar panels on its roof, which offset about five per cent of the building's electric usage. The building's roof is one of the largest photovoltaic installations on the East Coast. The photovoltaic system converts the sun's light into electric energy and feeds it directly to the building. Another benefit of the roof is that it provides extra thermal insulation. It not only generates electricity but it mitigates unwanted radiant heat gain.

NOAA's Satellite Operations Facility (NSOF) in Suitland, Md., also has an innovative roof. The building has one of the largest so-called "green" roofs in the Washington D.C. area. It has soil and native plantings on the roof much like a sod shanty from pioneering days.

"The building is very unique," says Paul Pegnato, NSOF project manager. "The architect had this vision of a sloping landscape. So when you start on the north side and are walking across the landscape, you're walking across the roof without even knowing it."

NSOF's green roof helps reduce storm water runoff and improves the building's insulation. But NOAA has run into some problems maintaining the roof's plants during periods without rain.

"We've had some droughts out here, and there isn't a lot of experience here with green roofs," Pegnato says. "We're fighting with that. It takes a lot of commitment to maintain the landscaping."

The landscaped roof helped NSOF, a 60,000 square foot building with 549 employees, receive the LEED Gold rating in early November.

The Air Force Weather Agency is building a 182,000-square-foot building at Offutt Air Force Base in Omaha, Neb., that is aiming for LEED certification. The building, which cost US$29.7 million, houses supercomputers that process more than a terabyte of weather information each day and transmits it to pilots around the world.

The Air Force is using several design tricks to get the building certified under Version 2.1 of the LEED standard.

"It's unclear if the building with its large, powerful computers could get certified under Version 2.2...because 2.2 requires the entire energy load to be considered," says Lt. Col Ron Dunic, Chief of AFWA Headquarters Transition Programs. "We tried to get as much of the energy efficiency in other parts of the building to reduce the overall energy footprint of the building."

Some of the tricks the Air Force used include angling the building to face the west rather than the south to reduce summertime heat. The building also has a reflective white roof with extra insulation to keep the sun from warming up the building too much.

"One of the big things is the raised floors," says Bruce McCauley, chief of construction management at Offutt. "The three-foot raised floor allows us to distribute the wiring and the air conditioning and heating under the floor. We do get some energy efficiency by not having ducts."

The Air Force hopes to get points on the LEED certification process for features that are outside the building itself. For example, the new building is alongside an abandoned runway. So the Air Force reused the runway for the parking lot and will get points for recycling existing materials and reducing construction waste.