LEGISLATION
THE CHANGING FACE OF TALL BUILDINGS
T
he façade of a building is often interpreted as an indication of what is inside, even though this perception has been challenged countless times, resulting in the
idiom – “It’s only a façade”.
The façade of a building is the first to greet visitors and users. This is especially true for public sector real estate, which finds itself under more intense scrutiny and analysis than any other property sector. The introduction of Display Energy Certificates for larger public sector buildings and the latest changes to the Approved Document Part L (2013) have only added to the constraints which govern the management of these properties, not to mention the difficulty in dealing with the great variety of buildings of different designs and ages.
However, in a rapidly changing world, the public sector needs to be seen as a role model, including in the sustainability and energy efficiency aspects of building management. The changes being brought by the desire to improve building energy efficiency are similar to the changes which have led to façade engineering becoming a standalone profession. This shift is based on the increased complexity of the façade systems employed in designing and building new forms as well as the need to ensure long term performance with low maintenance costs.
In order to understand why public sector real estate is changing, it is necessary to consider the impact of the latest updates to relevant legislation as well as advances in façade design and materials. These aspects are relevant for all types of properties, although they become more evident in tall buildings.
MAIN TYPES OF FAÇADES There are two basic types of façades: traditional and modern. The main difference is that traditional façades are generally loadbearing while modern façades tend not to be. However, the division in two main façade types is very general and needs to be caveated by mentioning that modern façades are generally understood to be represented by curtain wall façade systems although this is only one of the many modern façade systems. A curtain wall façade is a non-loadbearing external skin generally defined by modularity and flexibility. There are several types of curtain wall façade systems: The so-called ‘stick’ system which is made up of metal profiles (generally made from aluminium) called mullions and transoms which are assembled on site to create a grid or frame. The Double Glazed Units (DGUs) are then secured to the framing
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with pressure plates which in turn may be covered with architectural capping profiles.
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The unitised façade system comprises the same components as the stick system but all the components are assembled in a factory-controlled environment and then delivered to site for installation. This system is widely used today, accounting for most of the façades in modern buildings and generally the only suitable façade system for tall buildings due to speedy installation times. Panelised façade systems are similar to the unitised system but the prefabricated modules are generally much larger and can accommodate different types of materials and components, such as precast concrete, metal framing and windows. Precast concrete façade modules are cast in moulds in a factory-controlled environment and then delivered to site to be installed, usually by crane.
Other modern types of façades are defined by their extensive use of glass and metal connections and are known as structural sealant glazing or structural glazing (such as bolted or suspended assemblies). These façade systems will give the façade a smooth surface. Early modern buildings have used a combination of traditional construction with modern façade systems (not curtain walls). Typically, most of the façade has a stone or precast concrete finish with windows installed as vertical or horizontal ribbons or individual openings.
It is important to distinguish between the different types of façades as this will dictate the availability of options for improving the building fabric energy efficiency.. The relatively new goals and targets for increased sustainability and energy efficiency are in contrast to a historical legacy of ineffective and inefficient running of the estate.
THE FABRIC OF THE PUBLIC SECTOR ESTATE
The difficulty in dealing with the public sector estate when considering the availability of options for fabric improvement lies also in the different types of real estate ownership. Generally, the long-term perspective in property management prevails. However, this may not always be compatible with certain types of ownership such as short-term leasehold. It is only where the site is owned outright that the full improvement potential can be unlocked.
Another aspect which needs to be considered is the building usage and the need
PUBLIC SECTOR ESTATES MANAGEMENT • JANUARY 2015
for business continuity. This is true for all types of buildings and especially so for hospitals and social housing. In conjunction it will be required to carefully assess the options for façade improvement in order to identify the most cost-effective and least disruptive route. At this stage the input of a façade engineer is required and subsequently throughout the project so that the long-term performance requirements can be achieved within time and on budget. For instance the façade refurbishment of
Guy’s Tower in London, the tallest hospital building in the world, took two years and was carried out without interrupting the hospital activity. This was possible with careful consideration being given from the outset to adapting the new façade design to the existing building in order to identify the most suitable option. Universities ‘benefit’ from the legacy of the 1950s – late 1970s construction boom, when many high rise buildings were built using modern façade systems, mainly precast concrete and stick curtain walls. However, the façades have not been upgraded to reflect advances in materials, technology and architectural trends, even though the mechanical and electrical equipment has usually been updated. Without an upgrade of the façade it will not be possible to utilise the new services to their full capacity. Furthermore, although façade improvements may be considered capital expenditure, they have a longer life than services, so in the long term the façade investment will be recovered and there will be full benefit from the improved façade performance and aesthetics. One such example is the Arts Tower in Sheffield, a Grade II* listed modernist building. The tower is owned by the University of Sheffield and was completed in 1966 with a modern façade comprising a basic aluminium curtain wall system. After 45 years of service, the decision was made to replace the entire façade with a modern system similar to the original façade. In a project of this type the improvement on performance compared to the original construction is relatively easy to attain. Difficulties arise when other aspects such as listed building status or vacant possession need to be taken into account. A clear distinction becomes evident between existing buildings and new build construction in regards to options for improvement.
IMPROVEMENT OF EXISTING BUILDING FAÇADES
It has been successfully argued that improvement of existing buildings is more sustainable than demolition and replacement
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