TM59 report and overheating assessment
A TM59 report records a design-stage assessment of overheating risk in homes using dynamic thermal modelling, declared assumptions, weather data, room-by-room results and mitigation evidence.
A TM59 report records a design-stage assessment of overheating risk in homes using dynamic thermal modelling, declared assumptions, weather data, room-by-room results and mitigation evidence.
What this report needs to prove.
The page targets “TM59 report” while keeping the report-template query on its own page.
What the report answers
It records whether the assessed dwelling types and rooms meet the applicable overheating criteria, which cases govern and where mitigation is needed.
What the model must declare
Geometry, constructions, glazing, shading, ventilation, internal gains, occupancy profiles, weather data, controls and every project-specific departure.
What the reviewer should see
A clear sample strategy, model QA record, results by room, failed cases, sensitivity checks, mitigation changes and the final issue basis.
How to prepare the assessment and report.
Use controlled source information, keep each modelling decision traceable and obtain competent-person review before issue.
Confirm the assessment basis
Record the applicable TM59 edition, planning or Building Regulations route, project stage, weather files and approval requirements before modelling.
Build and check the thermal model
Coordinate zoning, constructions, openings, shading, gains, profiles and control logic against the current architectural and MEP information.
Run the required cases
Assess the agreed dwelling sample and scenarios. Keep the raw outputs, model version and any sensitivity runs tied to the report issue.
Review failures and mitigation
Explain each failed room, test passive measures first, record design changes and rerun the controlled model before drawing a conclusion.
Assemble the report
Present the basis, assumptions, QA checks, results, mitigation and limitations so another competent modeller can audit the submission.
Information to gather before you start.
Missing inputs should remain visible as review items. They should not be replaced with convenient assumptions without approval.
| Input group | Source information | Why it matters |
|---|---|---|
| Assessment brief | Client requirements, planning conditions, Part O route and agreed TM59 edition | Defines the test and approval boundary |
| Geometry and fabric | Current drawings, room areas, constructions, glazing, orientation and shading | Controls solar and fabric heat transfer |
| Ventilation strategy | Openable areas, controls, restrictions, mechanical rates and operating schedules | Defines how heat is rejected |
| Internal gains | Occupancy, lighting, equipment, hot-water and distribution losses where applicable | Sets the heat-gain profiles |
| Weather and scenarios | Declared current and future weather files where required by the brief | Makes the model basis reproducible |
| Simulation outputs | Room temperatures, occupied hours, criteria results and model QA exports | Supports the reported conclusion |
What the issued report should contain.
Use the separate template page when the search task is to find the report layout rather than understand the assessment.
| Section | Required coverage |
|---|---|
| Executive summary | Assessment scope, headline outcome, governing cases and required design actions. |
| Project and regulatory basis | Building description, project stage, applicable TM59 edition, Part O or planning context and responsibilities. |
| Model methodology and QA | Software, model version, geometry checks, zoning, weather data, profiles, ventilation, gains and assumptions. |
| Sample and scenario matrix | Dwelling types, rooms, orientations, floors, weather cases and mitigation options assessed. |
| Results | Room-by-room criteria tables, key plots, failed cases and corridor results where applicable. |
| Mitigation and conclusion | Design changes, rerun evidence, residual risks, limitations and competent-person sign-off. |
Standards and guidance to check.
The project team must confirm the current edition, jurisdiction, contractual requirements and authorised access to each publication.
- CIBSE TM59 2026 launchCIBSE published the updated design-stage methodology in July 2026. Confirm which edition applies to the project.
- Approved Document O FAQsFor England, the government explains the dynamic thermal modelling report expected for the Part O route.
Prepare the report in Adelphos Chat.
Collect the inputs, identify missing evidence and build the report structure now. Report Studio templates are being prepared for release.
TM59 report and overheating assessment questions
What is a TM59 report?
A TM59 report is the auditable record of a residential overheating assessment. It states the modelling basis, assumptions, sampled dwellings, room results, mitigation and conclusion against the applicable TM59 methodology.
Is TM59 the same as Part O?
No. TM59 is a CIBSE assessment methodology. Approved Document O is regulatory guidance for new residential buildings in England and includes a dynamic thermal modelling route that refers to TM59.
Which TM59 edition should a report use in 2026?
CIBSE published an updated TM59 methodology in July 2026. The modeller should confirm the edition required by the client, planning authority and building control body, then state it clearly in the report.
Can Adelphos create the final compliance decision?
Adelphos can structure evidence and draft the report, but a competent modeller remains responsible for the model, assumptions, interpretation and issued conclusion.
Continue with the evidence.
Move between the technical guide, the report structure and the calculation tools without mixing their search intent.
Adelphos structures declared evidence and report content. A competent person remains responsible for the model, calculations, standards, assumptions, interpretation, coordination and issued conclusion.