RENOVATION
Carbon reduction The environmental impacts of the facade refurbishment were assessed by Arup’s facades and materials specialists based on a life cycle assessment (LCA) process to show positive impacts from day one and how these impacts would be reduced in the future. Impacts against six environmental categories were assessed for six facade types and then multiplied by the planned area of each type. A carbon ‘payback’ analysis was then undertaken, calculating the initial carbon ‘spend’ and the annual carbon savings, plotted on a graph. The results were
compelling – over 18,000 tonnes of CO2 would be avoided compared to a new build, over 8,000 tonnes saved over 30 years and a carbon payback point of around 12 years.
The challenges There were a number of significant challenges for the Arup team to overcome. Although all of the inpatient beds had already been moved out, there was no space into which to decant occupiers and the building had to remain operational throughout design and construction. Managing disruption would therefore be a key priority. There were also considerable logistical
problems to be overcome. Over time since 1974, podium buildings and atria had been added and today the tower only touches the ground externally on the western face of the User Tower, so getting access to work on the facades required significant temporary works. Planning contractor’s compounds would also be difficult in a congested, live hospital site.
Approach Although the benefits had been established, a practical approach to design and delivery still needed to be developed. In the User tower in particular, the need to minimise disruption, avoid intrusion into clean environments such as the pharmacy manufacturing unit pointed
8,000 6,000 4,000 2,000 0
-2,000 -4,000 -6,000 -8,000 -10,000
Initial carbon spend
Payback point
New façades for the Communications and User tower window bays.
in the direction of a flexible design solution being required. The design team also wanted to provide a solution that would allow further improvements to be made in the future, such as the introduction of natural ventilation through mixed mode cooling. For the Communications tower, the only
realistic solution was to repair the damaged concrete and seal the facade in a new skin that would prevent further deterioration and contain any subsequent loose material. A distinctive and bespoke profiled, anodized aluminium rain screen cladding design was selected. At the same time, Arup’s access specialists designed a new monorail cleaning system to replace the inoperative existing one. For the User tower, having first stabilised
the concrete surface, a new thermal layer was designed by Penoyre and Prasad. This high performance layer will be placed in a line just in front of the existing columns to provide a new thermal line, up the building, to minimise thermal bridging. Solar selective glass will be used to control
the balance between solar gain in summertime (which adds to cooling loads) and natural light admittance, and will respond to the orientation of each facade. This innovative solution was designed to
be fitted in front of the existing windows which allows them to be removed where possible, or left in place until a future refurbishment, where removal is not practical. The successful development of the design
resulted from a partnership approach between the Trust projects and estates teams, the Arup team, the building users and specialist supply chain members.
Successful delivery No project of this nature could be attempted without the assistance and cooperation of the building users and the client’s asset management and operations staff. The Arup team began an extensive process of stakeholder engagement at an early stage, keeping them informed on progress at regular intervals, and this paid dividends in the longer term. In order to plan the works at a floor and department level, questionnaires were designed to gather as much information on working arrangements, risks and hazards as possible. The project is currently on site with the
appointed contractor. Due to the fact that the building users will remain in occupation throughout, for delivery of the construction works the overriding principle was to work from the outside wherever possible. The User tower balconies facilitate this in part, but there remain parts of the facade that require working safely at considerable height and above glass atria. Access is also difficult, but with early design by Arup’s construction planners and final design of the substantial temporary works by the contactor, a system of gantries, crash decks, roof-mounted hoists and wall climbers that will support delivery of the project has been developed.
Total carbon saved 0 1 2 3 4 5 6 7 8 9 10 1
1 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Number of years
The environmental impact of the facade refurbishment was assessed, based on a life-cycle assessment process.
64
Conclusion Guy’s Tower is a good example of what can be achieved with the refurbishment of an old building that would once have been considered beyond salvaging, or at the least not worthy of the investment. By taking a different approach, not only will the Trust have delivered an exemplar major refurbishment on an occupied building, it will also have continued its remarkable record in terms of reducing energy consumption and improving carbon performance.
IFHE DIGEST 2013
Carbon ‘spent’/‘saved’ (tonnes CO2
e)
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