TM52 vs TM59: which overheating standard applies?
TM52 assesses overheating risk in non-domestic buildings; TM59 applies the same adaptive principles to residential buildings with stricter bedroom criteria.
Both are CIBSE methodologies built on adaptive thermal comfort and both rely on dynamic simulation, so the modelling effort is similar. The difference is the building type and the criteria applied. TM52 tests three criteria across occupied hours in non-domestic spaces. TM59 adds residential-specific occupancy profiles and a separate, tighter night-time criterion for bedrooms, reflecting the fact that sleep is where overheating causes most harm.
TM52 vs TM59, attribute by attribute
| Attribute | TM52 | TM59 |
|---|---|---|
| Building type | Non-domestic | Residential |
| Criteria | Three adaptive comfort criteria | TM52 criteria plus bedroom night-time limit |
| Occupancy profile | Standard non-domestic patterns | Prescribed residential profiles |
| Common trigger | Planning, Part O interaction, design assurance | Planning conditions on residential schemes |
| Method | Dynamic simulation | Dynamic simulation |
Which one applies to you
Choose TM52 when
- /Offices, schools, healthcare or naturally ventilated commercial space
- /A planning authority requires overheating evidence on a commercial scheme
- /You want to avoid specifying comfort cooling if the design can avoid it
Choose TM59 when
- /Build-to-rent, student or residential elements of a mixed-use scheme
- /Planning conditions cite TM59 explicitly
- /Bedrooms rely on openable windows for night cooling
Mixed-use schemes frequently need both in one model — the commercial podium assessed under TM52 and the residential tower under TM59 — which is far cheaper to run as a single exercise.
Common questions
+Does Part O replace TM52 and TM59?
No. Part O is the building regulation for overheating in new residential buildings in England, and its dynamic route is based on TM59 methodology, so the CIBSE work still underpins it.
+When should overheating analysis be done?
At RIBA Stage 2 or 3, while glazing ratios, shading and ventilation strategy can still change without cost.