Saeed Azarshab

Approved Document O: Overheating

Statutory guidance · England-focused reference · Editorial source review:

Part O addresses overheating in new residential buildings within its scope. It is not a blanket retrofit rule for all existing buildings. The assessment route and mitigation need to reflect the actual design, including glazing, shading and the practicality of removing excess heat without creating other safety or usability problems.

Independent explanation, not an official approval or project-specific legal/design advice.

When to use this guide

  • Designing a new residential building within Part O’s scope
  • Changing glazing, shading or a relevant ventilation strategy before construction
  • Checking overheating assumptions and the suitability of mitigation

What to check

Use these prompts with the responsible project team. Ticking a box does not certify compliance.

You can tick these prompts while reviewing the project.

Download checklist (TXT)

Keep these records

  • Overheating assessment and design assumptions
  • Coordinated mitigation details and changes
  • User information on the intended strategy

Common mistakes

  • Applying Part O indiscriminately to every existing property.
  • Assuming an opening window is a usable mitigation without considering its real constraints.

When to get specialist help

Get competent assessment advice for uncertain scope, difficult sites or designs whose mitigation depends on unrealistic occupant actions.

Scope and edition

Landing updated 15 June 2022 and links corrected guidance and official FAQs. Confirm the project transition and assessment route. Do not present Part O as a blanket requirement for all existing buildings. Coordinate overheating mitigation with noise, security, safety and ventilation.

Overheating mitigation in new residential buildings.

Use the official source to check the current text, amendments not yet incorporated, commencement and project-specific transition. A published future edition is not automatically the rule applying to your work.

Official sources

Source links lead to external official websites. We provide original explanatory notes and do not reproduce paid standards.

About this library

Independent, plain-English reference notes by Saeed Azarshab. The library covers the 42 subjects listed here; it is not every law affecting construction, an official government publication or a project-specific compliance decision. Building Regulations, Approved Documents, workplace safety duties and planning permissions have different roles.

Editorial source review: . Check the current official text, commencement dates, outstanding amendments and transitional arrangements before relying on a requirement. Publication date is not necessarily the date a rule applies. A relevant competent professional or authority must resolve project-specific questions.

Sources and lawful reuse

Contains public sector information licensed under the Open Government Licence v3.0, except where otherwise stated. These are original practical summaries, with links to the official material. No government endorsement is implied. We do not host copies of proprietary BS, ISO or Eurocode standards, third-party diagrams or publisher layouts. Check each source’s rights notice before reuse.

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