CIBSE Technical Memorandum 52 (TM52)

CIBSE TM52 provides a standardised methodology for predicting overheating risk for commercial building designs using Dynamic Simulation Method (DSM) also known as dynamic thermal analysis.

TM52 consists of three criteria which, together, indicate when overheating is likely to be problematic. The three criteria for overheating are all defined in terms of ∆T, which is the difference between the actual operative temperature in the room at any time and the limiting maximum acceptable temperature.

The three criteria are:

Criterion 1 - Hours of Exceedance

The first criterion sets a limit for the number of hours that the operative temperature can exceed the threshold comfort temperature by 1 K or more during the occupied hours of a typical non-heating season (1 May to 30 September).

Criterion 2 – Daily Weighted Exceedance

The second criterion deals with the severity of overheating within any one day which is a function of both temperature rise and its duration.

Criterion 3 - Upper Limit Temperature

The third criterion sets an absolute maximum daily temperature for a room, beyond which the level of overheating is unacceptable.

In TM52, a room or building that fails any two of the three criteria is classed as overheating.

How can we help you?

We can assist you assess the risk of overheating in your commercial building project either as part of local authority requirements, your requirements or your clients' requirements. To discuss your requirements, please contact us on:


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