CIBSE updates TM59 overheating risk
6th July 2026
UK: CIBSE has updated TM59 with revised guidance for assessing and mitigating overheating risk in new homes and major residential refurbishments.
Produced in collaboration with Arup and Loughborough University, TM59 Overheating risk in dwellings: A design stage methodology, is referenced within Part O of the Building Regulations and is widely recognised as a key industry resource.
The updated publication reflects the latest research, industry experience and evolving understanding of how homes can be designed to remain comfortable and resilient in a warming climate.
The guidance comes at a time when overheating is becoming an increasingly important issue across the residential sector in the UK.
The publication incorporates updated approaches to evaluating bedroom overheating, informed by recent research undertaken by Loughborough University and includes revised modelling guidance for ceiling fans, recognising their role as an effective low-energy measure for improving occupant comfort.
A key enhancement within the new edition is the requirement for all homes to be assessed under unconstrained conditions using future weather files representing the 2050s climate.
This approach places greater emphasis on passive design measures at the earliest stages of development, helping designers create buildings capable of maintaining comfortable internal conditions without relying on energy-intensive cooling systems.
