I pulled out the latest issue of Green Futures for a bit of light relief. It instantly lifted my mood as it reminded me just… how exciting sustainability issues can be.
Work is about to begin on Guy’s Tower, London, giving its crumbling walls a sleek new shell.
The Shard may be attracting admiring glances from far-flung corners of London, but another tower in its shadow has a more interesting story to tell.
At 143 metres, Guy’s Tower is the tallest hospital building in the world, and a notable feature of the Thames skyline since the 1970s. It gives the hospital a sixth of its floor space, and offers charity abseilers a good bit of wall to jump down. But in recent years, it’s been falling apart: small pieces of concrete have, rather alarmingly, started to fall off the towers. At a cost of tens of thousands of pounds a year, the Guy’s and St Thomas’ NHS Foundation Trust has been sending professional abseilers up the tower “to hack off loose bits to save anyone below being hit” – as Alastair Gourlay, the man in charge of developing the Trust’s estate, puts it.
It’s high time for some TLC on the building’s façade. The trigger point may be public safety, but it’s an opportunity to change much more about the building and how it functions as a hospital. “Good retrofit is all about being able to understand the way a building currently works”, says Neil Allfrey of architects Penoyre & Prasad, who, with Arup, were selected to design and implement the makeover. “I wouldn’t say Guy’s Tower is particularly attractive but you work with what’s there”, he adds. “Knocking it down was considered, but rejected [as financially unviable].”
The result will be a much better reflection of the high quality of our medical care
So let’s take a closer look at the problems the team faced. Guy’s isn’t actually one tower, but two, joined by a bridge at each floor. The larger User Tower houses all sorts of specialist departments, from the King’s College London Dental Institute, to assisted conception, to chemotherapy. The taller Communications Tower is taken up by lifts, stairs and shafts. Working with the NHS Trust, Penoyre & Prasad and Arup analysed the use of the building, its thermal habits and its performance in great detail. Replacing the services was not currently an option but the old façade designed in an era free of energy and climate worries was causing significant heat loss; and that had to be the first target.
The team put forward a number of options covering issues such as how much of the façade to reclad, how to deal with cold bridging [where the insulation layer is penetrated by bits of structure], and how to work around the occupiers in-situ. Each option was thermally modelled and plotted on a graph of cost versus energy efficiency gain. Laid out in this way, it was easy to see where the greatest green gain could be achieved while keeping costs reasonable. “There’s a point on the curve when you can spend a lot more, yet gain very little energy efficiency”, said Allfrey.
In the end, the team decided that the most cost-effective solution was to fit a new façade in front of the existing columns of the User Tower, and to fully clad the Communications Tower with an aluminium ‘rainscreen’. Glazing was selected to minimise heat loss and reduce solar gain. The project, which begins in early 2012, is seen as a first step to a low-carbon Guy’s Tower, and should cut annual carbon emissions by 15-20%. “It’s not a massive saving,” admits the Trust’s Alastair Gourlay, “but it will avoid 8,000 tonnes of CO2 being pumped into the atmosphere over 30 years. And the result will be a much better reflection of the high quality of our medical care. We want to be working in an environment that reflects the excellence of our clinical standards, and costs less to run. I feel very excited about it.” – Charlotte Sankey
Photo: Penoyre & Prasad