UCL Energy Institute


CIBSE TM 49 Design Summer Years for London


1 May 2014

CIBSE Design Summer Year (DSY) for London is the most appropriate year of weather data to assess the summertime cooling needs of buildings in London. / The new CIBSE guidance TM49 and the accompanied Design Summer Years for London enable designers to analyse the summer performance of their buildings and investigate the impact of urban macroclimatic factors and climate change when carrying out overheating risk assessments for buildings in London. / Urban centres, especially in the south and south east of the UK, will experience more intense and frequent summer hot events, exacerbated by the urban heat island (UHI) effect. The UHI effect is a result of the dense built up of urban centres and the lack of green areas and manifests as a temperature difference between the urban centres and their rural surroundings. The TM49 Design Summer Years for London and the accompanied datasets for building thermal simulation, introduce the concept of incorporating the UHI effect and the severity of hot events in the design of buildings. Specifically, instead of having a single DSY for London (using observed data from Heathrow), three DSYs are now available capturing the local climate in three different London sites (urban, semi-urban, and rural) and for three years of varying severity of hot events. / Designing just for present weather conditions will leave buildings vulnerable to changes in climate. The availability of future climate projections helps in identifying the impacts that a changing climate will have on building performance and building vulnerabilities to future weather events. The currently available UK Climate Projections (UKCP09), released by DEFRA in 2009, are probabilistic in nature, to better quantify the climate uncertainty. This probabilistic nature encourages the better understanding of future risks when adapting to a changing climate. Future DSYs for London are also available to reflect the UKCP09 climate projections and allow designers to increase the resilience of their buildings to future changes in climate.

Design Summer Years for London. (CIBSE TM49 ). Chartered Institution of Building Services Engineers: London, UK. 

Hacker, JN; Belcher, S; White, A; (2014)