High rise residential buildings are increasingly being designed and built in the UK, and London leads the way, with around 25 residential buildings of 20 storeys or more under construction and around another 80 with planning consent. Many more are in the pipeline.
At the same time, building regulations and planning requirements are placing increasingly stringent demands on the energy performance of new buildings. In April 2014, the latest version of Part L was introduced, which included the requirement for residential buildings to meet new fabric energy efficiency (FEE) standards. Compared to previous versions of Part L, the FEE standard represents a wholesale change in how the passive performance of new buildings is controlled, for the first time looking holistically at the performance of the home rather than just the thermal performance of each aspect of the structure in isolation.
The 2013 FEE standard was designed in part to keep the regulations on the path to the introduction of zero carbon homes in 2016, and represents a sensible and workable solution for the majority of the UK’s new build housing stock.
However, the impact on high rise residential schemes does seem to have been rather overlooked. More often than not, the only viable type of wall construction is a unitised curtain walling system.
The characteristics of curtain walls are often not well understood outside the facades community. Up to 80% of heat loss can be through the framing, and unlike more traditional construction techniques, increasing solidity and more insulation often doesn’t translate into improved thermal performance.
Most critically, based on our experience at WSP we believe it is impractical or impossible for high rise buildings to meet the new FEE standard; the façade thermal performance necessary to meet the standard being much better than could be achieved using unitised façade systems.
Future advances in façade technology may bring compliance within reach; glass-reinforced plastic cladding solutions for example are likely to offer much improved thermal performance compared to today’s aluminium systems.
Until those advances reach the mass market place, the industry faces a dilemma. Do building control bodies accept that high rise residential schemes cannot meet the requirements of Part L in full, or have we legislated away one of the solutions to Britain’s housing crisis?
- Andrew Bickerdyke is an associate at WSP building services