CIBSE TM59
& TM52
Dynamic thermal modelling — residential & non-domestic.
Overheating risk has to be demonstrated, not assumed. We carry out CIBSE TM59 (residential) and CIBSE TM52 (non-domestic) assessments using dynamic thermal modelling — the detailed route to proving compliance with Part O and satisfying planning requirements.
- TM59 residential & TM52 non-domestic
- Part O compliance & London Plan SI 4
- Practical mitigation advice included
TM59
Residential Dwellings
TM52
Non-Domestic Buildings
Part O
2022 Regulations
SI 4
London Plan Ready
What is a TM59 or TM52 assessment?
CIBSE TM59 and TM52 are the industry-standard methodologies for demonstrating overheating risk using dynamic thermal modelling — hourly simulation of internal temperatures across a CIBSE design-summer-year, accounting for the building design, orientation, glazing, shading, thermal mass and ventilation strategy.
TM59 is used for residential dwellings: new homes, apartments, student accommodation and institutional residential buildings. It tests habitable rooms against the Part O overheating criteria. TM52 is used for non-domestic buildings: offices, schools, libraries and similar occupied spaces. It assesses against adaptive comfort criteria rather than fixed temperature thresholds.
Why do you need one?
Dynamic modelling is required where the Part O Simplified Method cannot accommodate the design — typically where glazing ratios are high, dwellings are single-aspect, or the site is urban and heat-affected. It is also required by most London boroughs under London Plan Policy SI 4, and by many other planning authorities for major schemes. For non-domestic buildings, TM52 is the recognised route to demonstrating overheating has been properly considered at design stage.
Design freedom as well as compliance
Because dynamic modelling takes full account of shading, glazing specification, ventilation strategy and thermal mass, it can unlock designs — more glazing, less conventional orientations, specific layouts — that the Simplified Method would reject. Used early in design, it is a tool as well as a compliance hurdle.
TM59 or TM52?
The methodology depends on building type. We confirm which applies — and whether the Part O Simplified Method might also be suitable — before you pay for anything.
Residential Dwellings
The dynamic compliance route under Part O for new homes, flats, apartments, student accommodation, care homes and other institutional residential buildings. Tests habitable rooms against Part O overheating criteria using hourly simulation across a CIBSE design-summer-year.
- Part O “dynamic” compliance route
- Required by London Plan Policy SI 4
- Credits shading, g-value & ventilation strategy
Non-Domestic Buildings
For offices, schools, libraries, healthcare and other non-domestic occupied spaces. Assesses overheating against adaptive comfort criteria, accounting for the fact that occupants in non-domestic buildings can adapt their behaviour and clothing more easily than residential occupants.
- Offices, schools, healthcare & more
- Adaptive comfort criteria
- Planning & design-stage use
London Plan & Major Schemes
London Plan Policy SI 4 requires overheating risk to be reduced through the cooling hierarchy, and most London boroughs require a TM59 for any residential scheme. Major schemes outside London increasingly require TM59 or TM52 as a planning condition.
- GLA & London borough requirements
- Cooling hierarchy documentation
When the Simplified Method Suffices
For straightforward residential schemes within the Simplified Method parameters, dynamic modelling may not be necessary at all. We advise honestly — if the Simplified Method suits your design and no planning condition requires TM59, we will tell you so.
- Honest method advice before you commit
- Part O overheating assessments also available
The right method, right advice.
We carry out full dynamic modelling — not just screening tools — and sit alongside our overheating and energy service lines so the right method is always chosen for your scheme and budget.
Practical mitigation, not just a fail report
Where rooms or spaces fail the criteria, we recommend practical mitigation measures — shading combinations, glazing specification, ventilation strategy — so you can update the design rather than start again.
Dynamic Modelling, Not Just Screening
Full CIBSE TM59 and TM52 dynamic thermal modelling — not the simplified screening tool. Hourly simulation against CIBSE design-summer-year weather data for every assessed room or space.
Right Method for Your Project
We advise which methodology — TM59, TM52, or the Part O Simplified Method — best suits your scheme and budget before you commit to anything.
Residential & Non-Domestic
TM59 for dwellings and institutional residential buildings; TM52 for offices, schools and other non-domestic occupied spaces — one provider for both methodologies.
Planning & Building Control Reports
Full compliance reports accepted by building control and planning authorities, including the GLA and London boroughs requiring TM59 under London Plan Policy SI 4.
Practical Mitigation Advice
Where rooms or spaces fail the criteria, we recommend practical, cost-effective mitigation measures — shading, glazing specification, ventilation strategy — so you can update the design confidently.
Nationwide, Fast Turnaround
Residential and non-domestic schemes across England, Wales, Scotland and Northern Ireland. Fixed prices, clear timescales, and design-stage engagement so problems are solved early.
Four steps to your overheating report.
From initial plans to a full compliance report accepted by building control and planning. Mitigation advice included where any room or space requires it.
Model Build
We create a dynamic thermal model from your plans, sections and elevations, using CIBSE design-summer-year weather data for the correct location and building type.
TM59 / TM52 Analysis
We run the hourly simulation, testing each habitable room (TM59) or occupied space (TM52) against the relevant overheating criteria.
Results & Mitigation
Where rooms or spaces fail the criteria, we advise on practical mitigation — glazing specification, external shading, ventilation strategy, openable areas — so you can update the design.
Compliance Report
A full written compliance report for building control and / or planning — documenting the model, methodology, results and any mitigation measures adopted.
Quoted per scheme.
TM59 and TM52 are priced on the number of rooms or spaces to be assessed and the complexity of the building. Send us plans and we will confirm which methodology applies and quote a fixed price.
Priced per scheme based on methodology (TM59 or TM52), number of rooms or spaces assessed, and scheme complexity. Send us plans for a fixed-price quote, with method advice included before you commit.
- Full dynamic thermal model — not just screening
- TM59 (residential) or TM52 (non-domestic)
- Practical mitigation advice included
- Compliance report for building control & planning
*Priced per scheme. Contact us for an accurate quote. Related services: Part O overheating assessments, SAP calculations, London Plan compliance.
Get your TM59 / TM52 quote
Takes 60 seconds. No obligation. Working to a planning deadline? Tell us — we will prioritise your project.
TM59 & TM52 questions.
Everything you need to know about dynamic overheating assessments — the two methodologies, when each applies, and what happens if a room or space fails.
Still Got a Question? Ask Us What is the difference between TM59 and TM52?
CIBSE TM59 is the methodology for assessing overheating risk in residential dwellings — it tests habitable rooms against Part O criteria using dynamic thermal simulation. CIBSE TM52 covers non-domestic buildings such as offices, schools and other occupied spaces, and assesses against adaptive comfort criteria rather than the fixed Part O thresholds.
How does TM59 dynamic modelling relate to Part O?
Part O of the 2022 Building Regulations offers two compliance routes for new homes: the Simplified Method and CIBSE TM59 Dynamic Thermal Modelling. TM59 is the more detailed route — it is used when the Simplified Method does not suit the design (for example, because glazing ratios or orientations exceed the simplified limits), or when a planning authority requires it.
Is dynamic modelling worth the additional cost?
For glazed or urban schemes it often is. The Simplified Method applies fixed limits on window size and openable area; TM59 can account for external shading, glazing g-value, thermal mass and detailed ventilation strategy — and frequently passes designs the Simplified Method would reject. We will advise honestly which route is likely to suit your project before you commit.
Do I need TM59 or TM52 for planning?
It depends on the scheme and location. Major residential schemes and most London boroughs require a TM59 assessment under London Plan Policy SI 4 regardless of whether the Simplified Method would pass. Non-domestic schemes in some locations also require TM52. We will confirm what applies to your project at quote stage.
What design changes can help a TM59 assessment?
The most effective levers are external shading (brise-soleil, overhangs, balconies), lower solar-gain glazing (lower g-value), reducing glazing on south and west elevations, increasing openable window area, and specifying purge ventilation. We recommend the cheapest combination to achieve compliance — and it is far more cost-effective to make these changes at design stage than late.
What information do you need to carry out a TM59 or TM52 assessment?
Plans, sections and elevations showing room dimensions and window positions; a schedule of glazing (size, orientation, g-value if known); proposed construction build-ups; and a brief description of the ventilation strategy. We will tell you exactly what to send at quote stage.
What does the compliance report include?
A full written report documenting the dynamic model inputs, CIBSE design-summer-year weather data used, results for each room or space tested, a pass/fail assessment against the relevant criteria (TM59 or TM52), and — where any room fails — practical mitigation recommendations.
Do you cover all UK regions?
Yes. TM59 applies to new dwellings across England and Wales (Part O). TM52 is used for non-domestic buildings UK-wide. We carry out dynamic modelling assessments for schemes across England, Wales, Scotland and Northern Ireland.