New guidance published by the Chartered Institution of Building Services Engineers (CIBSE) aims to address the causes of overheating in homes, as the UK enters a summer that could be the hottest since 1976.

Addressing what the industry had identified as a gap in its knowledge, CIBSE has created the new 'Technical Memorandum 59: Design methodology for the assessment of overheating risk in homes' (TM59), in order to set a standard by which overheating can be assessed using a consistent methodology.

The new TM59, available as a free download and officially launched at University College London, has created a common approach that will see the whole industry consistently apply the same methodology. This approach may be crucial in the years ahead, with the MET Office reporting that the eight warmest years in the UK since 1910 have occurred within the last 14.

Input assumptions regarding occupancy profiles, internal gains, and natural ventilation capabilities will produce a wide variety of results and sometimes even mask the magnitude of overheating risk in some properties. TM59 aims to provide consistency across the industry, as all consultants will now be using the same assumptions regarding the use of the properties when assessing overheating risk.

Dr Anastasia Mylona, research manager at CIBSE, said “CIBSE has created this methodology in response to growing concern in the construction industry that rising temperatures and a changing urban landscapes are creating a generation of homes destined to overheat.

“By creating an industry-agreed standard methodology for assessing overheating, we aim to enable designers and engineers to work together to create buildings that are more resilient to hot weather events.”

TM59 draws on existing guidance produced by CIBSE and others on various aspects of a building’s performance to give a prescriptive approach to modelling, which will allow the methodology to be consistently applied. It also includes reporting requirements to ensure that stakeholders understand the methodology’s impact on the design.

Uniquely, TM59 draws on CIBSE’s own industry-leading weather data products, developed with the support of the MET Office, which plays a fundamental role in assessing whether a particular design is likely to overheat. The datasets are based on historical data collected from 14 sites around the UK since the early 1980s. In the current version, this data is combined with the latest climate change projections to produce future weather files up to the 2080s.

TM59 has been extensively ‘live tested’ on existing projects and shown to be effective, but CIBSE is planning to back up the results of the methodology through further research and testing as it is applied in the years to come. This will allow the methodology to be refined in response to new data and user feedback.