Achieving the 10% Draft London Plan Energy Efficiency Standards for Residential Buildings
The recently published Draft London Plan (December 2017) sets new, ambitious targets for the fabric energy efficiency of buildings. Following Grenfell, concerns surrounding the fire risk of PIR and phenolic insulation are making reductions in external wall U-values increasingly difficult in tall buildings, leaving the question of how these reductions in energy use will be achieved?
Policy SI2 of the Draft London Plan states that:
“Residential development should aim to achieve 10 per cent [improvement over Part L]… through energy efficiency measures”.
In the case of large scale residential development there are three likely areas of improvement needed to meet the new standard:
- Improvements to glazing, pushing the performance of double glazing (≈1.2W/m2.K) or requiring a switch to triple glazing (≈0.9W/m2.K). This could increase structural loads and can result in reduced heat and light transmittance.
- A switch to heat recovery systems for all homes (e.g. balanced mechanical ventilation or waste water). This will requiring additional careful design, duct/pipe runs and workmanship.
- Increased emphasis on assessing and improving the heat losses through thermal bridging junctions. The exact level of improvement needed will be dependent on the development scale and type of detailing. The assessment and improvement of heat losses through thermal bridging has gone unmonitored for the vast majority of large developments. Developers will have to adapt and change the way they approach the majority of these thermal bridging junctions in order to meet future targets.