As efficiency of buildings has improved the risk of overheating has increased, particularly in high-rise and densely populated areas . To combat this risk, Part O of the Approved Documents was adopted in 2021 and requires all new residential properties, including care homes, demonstrate compliance through one of two assessment methods, the simplified method or TM59 analysis.

The simplified method is usually the first step in establishing compliance and applies to dwellings with cross-ventilation (openable windows on opposite sides of a building), it can be used in both moderate and high-risk areas. A full TM59 overheating study using Dynamic Thermal Modelling (DTM) will be required if the simplified method fails to demonstrate compliance.

The London Plan and parts of Manchester require TM59 analysis on major projects at the planning stage. We recommend this as best practice for all projects as it can mitigate against design changes later in the project programme and be developed in tandem with the project's energy strategy.

We support the design team throughout the pre-planning phases to ensure compliance is met from an early stage and maximise opportunities for improved building performance.