An overcladding system will transform the Gallowgate Centre at Aberdeen College, in Aberdeen, Scotland, into a modern-looking and energy-efficient structure. Image by BPA Architecture, Edinburgh, U.K.
An “overcladding” project will leave a nearly 50-year-old academic center in the Scottish city of Aberdeen, in the United Kingdom, looking and performing like new.
April 2, 2013—A building that has been regarded as one of the ugliest in the Scottish city of Aberdeen, in the United Kingdom, is poised to undergo a dramatic face-lift that will transform its outdated appearance and greatly improve its energy efficiency without significantly altering its internal structure.
The Gallowgate Centre is the main building complex of Aberdeen College, a vocational education and training college with approximately 18,000 students and 450 employees. Located in the heart of Aberdeen, the center comprises a 10-story tower atop a podium, a 3-story building, and a single-story bridge that links the two. The center opened in 1964 and originally housed engineering and welding classes; today it accommodates everything from media and language courses to hairdressing and beauty laboratories.
Since opening nearly 50 years ago, the Gallowgate Centre’s interior has been updated to modern standards, but its exterior has remained largely unchanged and risks falling into disrepair with time. “It has been kept to a very high standard inside, and it’s been well maintained and serves its customers fairly well from that perspective,” says Duncan Abernethy, CEng, the project sponsor for Aberdeen College. “But externally, it just looks very, very tired now, and it doesn’t really reflect the high-quality provision that the college offers its students and other clients.”
Aberdeen College officials initially considered tearing down the Gallowgate Centre and building a new structure. But when they learned that other colleges and universities had successfully updated and preserved their buildings with “overcladding,” a process that involves installing new cladding over a building’s existing skin, the officials became intrigued and arranged to view a couple of completed projects. “That became quite attractive in terms of our environmental ambitions,” says Abernethy, who points out that the process essentially recycles an entire building. “It’s good from a financial standpoint as well,” he says. “It’s much cheaper to overclad than build new.”
The college put the project design out to tender, and as a result of that process it selected BPA Architecture, which is based in the Scottish city of Edinburgh. The firm specializes in overcladding projects and has made more than a dozen old buildings look and perform like new, including one of the buildings that Aberdeen officials visited during their scoping phase. “We have developed, over time, a detailed approach to doing this type of cladding project,” says David Burnett, RIBA, FRIAS, a founding partner of BPA Architecture. “What we do is we provide a highly insulated envelope behind a rain screen, which, combined with high-performance windows, give a very [good] U value.” (U is the heat transmission coefficient.)
Increasing the Gallowgate Centre’s energy efficiency is as important as improving its appearance, Abernethy says. At the moment, the center has singly glazed windows that leak air, in some cases to a marked extent. Some of the windows are rusted shut, preventing air circulation. “It can be very uncomfortable for clients in certain conditions,” Abernethy explains. “If it’s very cold in the winter, drafts can blow in around some of the windows, and it’s impossible to keep the building airtight. Equally, in the summer it can get very hot.”
BPA has proposed a two-layer overcladding system to address the Gallowgate Centre’s inefficiencies. Mineral wool insulation will be wrapped around the center’s existing exterior, and a pressure-equalized aluminum rain screen will then be installed on top of this. The rain screen will be supported by vertical rails that will attach to the building via brackets anchored into the existing concrete floor beams with resin. “The cladding support system, in fact, is bolted to the strongest part of the existing structure,” Burnett explains. “Nothing we are going to do will compromise the structure in any way.”
On the roof, polyurethane insulation will be applied directly over the existing rooftop and will then be covered by a single-layer membrane. The insulation will bring the U value down to approximately 0.18 W/m2 K, in line with U.K. regulations, Burnett says.
BPA has also specified high-performance, doubly glazed windows with a U value of 1.4 W/m2 K. The windows will feature toughened, low-emissivity glass inner panes, cavities containing argon gas, and outer panes of so-called solar control glass to reduce warming from the greenhouse effect. The windows will also have compression seals tested to more than 3,000 Pa, Burnett says. Although they will be installed in the same general spacing as the existing windows, the new windows will be smaller because the sills will be raised and the heads lowered. “The clever bit really is to get the alignment of the new external cladding to make the best possible match with the internal arrangement of the building,” Burnett says. “So, for instance, it might have been nice to alter the window spacing, but if you do that, then you have to alter the internal partitions and all that sort of thing. Retaining the pattern also minimizes disturbance of internal services and reduces cost.”
One advantage of the project is that all of the work will be conducted while the building remains in full operation, Abernethy says. “We have thousands of students here on any given day,” he says. “It would be a logistical nightmare to try to move them to different places and all of the equipment they need to train as well.” Keeping the building in full operation is possible because most of the work will be conducted outside using gantries, mast climbers, and scissor lifts. What is more, all of the interior work will be carried out at night or during other off-hours, Burnett says.
The project is currently out to tender as a design/build effort, meaning that the contractor will adopt the architect’s design proposals and use its own tried and tested construction methods to achieve the specification. Construction is expected to commence in the next two to three months, and completion is anticipated in the summer of 2014. Aberdeen College will then have a building with a contemporary look that will use less than half of the energy it consumes today. “It will certainly make a more attractive destination for students,” Abernethy says. “We’re excited about the design and looking forward to seeing it completed.”