CIBSE has updated its TM59 Overheating risk in dwellings: A design stage methodology, in collaboration with Arup, Loughborough University and Inkling. It offers revised guidance for assessing and mitigating overheating risk in new homes and major residential refurbishments.
Referenced within Part O of the Building Regulations, CIBSE TM59 is a key industry resource for evaluating overheating risk in residential buildings. 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.
Evidence shows many homes are vulnerable to excessive indoor temperatures due to extensive glazing, insufficient ventilation strategies and building designs that are not adequately adapted to future climate conditions.
The revised CIBSE TM59 strengthens the methodology used to assess overheating risk and supports the delivery of homes that are resilient, energy efficient and fit for the future. It incorporates updated approaches to evaluating bedroom overheating and includes revised modelling guidance for ceiling fans, recognising their role as an effective low-energy measure for improving occupant comfort.
A key update 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.
The updated guidance is expected to strengthen design stage decision making, improve consistency in overheating assessments and support the delivery of homes that are resilient to future climate conditions while reducing reliance on energy intensive cooling.
Ahmed Hegazi, Head of Knowledge and Digital at CIBSE, said: “Overheating is a present reality for households across the UK, and the built environment sector needs authoritative, evidence-based guidance to respond. This revision of CIBSE TM59 gives industry a robust foundation for delivering homes that remain safe, comfortable and resilient in a warming climate.”
CIBSE TM59 is available now from the CIBSE Knowledge Portal.