CIBSE TM52 Overheating Assessments
Walker Energy Analysis carries out CIBSE TM52 overheating assessments for non-domestic buildings across the UK, using dynamic thermal modelling in IES Virtual Environment. TM52 is the standard methodology for assessing overheating risk in offices, schools, and other commercial and free-running buildings, and it’s often required to support BREEAM’s HEA04 thermal comfort credit or a planning condition on natural ventilation.
Overheating risk in a non-domestic building tends to surface late, once occupants are in and complaining, unless it’s tested properly at design stage. A TM52 assessment gives you the evidence to catch it before the building is built, not after
The Three Criteria
TM52 assesses overheating in free-running and naturally ventilated buildings against three criteria, taken together. A room fails the assessment if it fails any two of the three.
Criterion 1 sets a limit on how often a room can get too warm: the operative temperature can’t exceed the comfort threshold by 1 degree or more for more than 3% of occupied hours during May to September.
Criterion 2 looks at how severe overheating is on any single day, since a short intense spike can be as much of a problem as frequent mild ones, and sets a daily limit for acceptability.
Criterion 3 sets an absolute maximum temperature a room should never exceed, regardless of the other two criteria.
We model each room against all three, using a full year of weather data and the building’s actual construction, glazing, shading and ventilation strategy, rather than relying on a single worst-case snapshot.
- Dynamic thermal modelling in IES VE, room by room, against a full year of weather data
- Testing against all three TM52 criteria, with clear reporting on where and why a room fails
- Whole-building or representative sample modelling, agreed with you based on the project’s size and risk
- Practical mitigation recommendations where a room fails, shading, glazing, ventilation strategy, or mechanical cooling where passive measures aren’t enough
- A report structured to support building control, planning, or BREEAM HEA04, depending on what the assessment is being submitted against
Where TM52 Applies
TM52 is the non-domestic equivalent of the TM59 methodology used for homes, and it applies to offices, schools, healthcare buildings, and other commercial or institutional spaces where occupants can’t simply rely on air conditioning to manage comfort. It’s commonly required at planning stage where a scheme relies on natural or mixed-mode ventilation, and it underpins the thermal comfort element of BREEAM’s HEA04 credit.
If your project also needs a BREEAM assessment or has a related planning condition, tell us early. The underlying modelling often overlaps, and there’s usually no need to run it twice.
Why work with us
We’re a specialist energy consultancy. This is the core of what we do, not a sideline. Every assessment runs through IES VE as standard, we turn changes around quickly, and results come back in a format your team, building control, or a planning officer can use immediately.
FAQs
Q: Is TM52 the same as TM59?
A: They’re closely related methodologies from the same CIBSE research. TM52 is used for non-domestic buildings, offices, schools, and similar. TM59 adapts the same principles specifically for homes, with its own pass criteria for living areas and bedrooms.
Q: Does a building have to fail all three criteria to be classed as overheating?
A: No, only two of the three. A room can fail the assessment even if it passes one of the criteria comfortably, if the other two show a problem.
Q: What happens if a room fails?
A: We identify what is driving the overheating risk and recommend practical changes, shading, glazing specification, ventilation strategy, or mechanical cooling where passive measures aren’t enough, then re-test to confirm the fix works.
Q: Do you model every room, or a sample?
A: It depends on the building. We agree the right approach with you based on the scheme’s size and overheating risk profile, sometimes that’s the whole building, sometimes a representative sample of the highest-risk spaces.
Get Your Overheating Risk Assessed Early
Talk to Walker Energy Analysis before your glazing and ventilation strategy is fixed, whether TM52 is needed for planning, BREEAM, or general design assurance.
