BR18 climate requirements and the documentation your project needs

• BR18 climate requirements distinguish the calculation duty from applicable limits.
• Building type and project scope affect the assessment.
• A4 and A5 have a separate construction-process limit for covered projects.
• Records and calculation assumptions need to be traceable at completion.

The client and project advisers should resolve BR18 climate requirements while design and procurement decisions remain open. Identify the competent calculation specialist and the parties supplying information. Contractors and subcontractors need to understand their agreed data deliveries without being expected to determine the whole building’s regulatory position themselves.

Begin with a brief scope note. Record the proposed work, relevant permit application date and building use. Check mixed uses and extensions explicitly. BR18 climate requirements cannot be selected from a single limit copied from another project. Keep the reasoning with the project documents so later design changes can be assessed against it.

Read the current provisions and the version applicable to the building case. BR18 climate requirements introduced from July 2025 include more project types, but there are exceptions. For example, certain residential and holiday-home extensions below 250 m² of heated floor area are exempt from the calculation duty. Obtain a specific assessment before relying on an exception.

Do not describe every refurbishment as covered new construction. Equally, avoid treating an extension as a refurbishment merely because it connects to an existing building. Ask the responsible adviser to explain the category and record the decision. BR18 climate requirements depend on that classification, which should be clear before the team starts collecting the calculation inputs.

For covered projects, BR18 climate requirements include separate limits for the relevant building life-cycle modules and for A4/A5. The construction-process limit is 1.5 kg CO₂-equivalent per m² per year. A low result in one part does not automatically compensate for exceeding the other limit.

Ask the calculation specialist to show these results distinctly. When preparing project information for BR18 climate requirements, label whether the data concerns products, site activities or another life-cycle module. The A4/A5 guide addresses practical site records. This overview addresses applicability and the information structure for the wider assessment.

Create an information list with the specialist preparing the calculation. Ask which quantities, product references and assumptions are needed, who supplies them and when. Under BR18 climate requirements, the calculation and its supporting documentation need to correspond to the project as delivered, rather than only an early design option.

Give each input a useful reference. Record the product or activity, quantity, unit and source of the information. Identify revisions where design or procurement changes affect the calculation. BR18 climate requirements are easier to manage when the information owner knows why a particular record is needed and how it will be used.

A substitute product can affect several different project deliveries. Ask the relevant adviser to review the change before treating it as acceptable for the climate calculation. BR18 climate requirements are one part of that review; structural, fire and other technical requirements may need separate consideration by the appropriate competent parties.

Retain the original and revised information with the decision. If a quantity changes, identify the updated source rather than editing a final total without explanation. This allows the calculation specialist to follow changes relevant to BR18 climate requirements and avoids losing the connection between a procurement decision and the issued assessment.

Official guidance provides different documentation routes, including project-specific information and permitted standard values for relevant construction-process inputs. Ask the calculation specialist which approach applies. BR18 climate requirements do not imply that every supplier must independently produce a complete building calculation.

Record assumptions and missing information explicitly. If the specialist uses an allowed value, retain the relevant reference and explain its use in the calculation. Do not disguise an estimate as measured consumption. For BR18 climate requirements, a reader should be able to distinguish supplied facts, permitted assumptions and unresolved inputs without searching through the entire email history.

Schedule a review while there is still time to resolve missing inputs. Check that quantities, selected products and site records correspond to the final project information. The applicable BR18 provisions require documentation of the calculation and assumptions at completion. Organise the delivery so the relevant reviewer can find both the result and its basis.

Use an index that distinguishes the issued calculation, input records and explanatory notes. Keep outstanding items visible. BR18 climate requirements should be addressed through a controlled delivery and review process. A polished summary page cannot replace missing inputs or establish that the calculations have been assessed by the appropriate competent person.

The changes discussed here entered into force on 1 July 2025. Application to an individual project depends on the relevant rules and dates. Sources were checked on 9 October 2026. Recheck BR18 climate requirements when the scope, classification or regulatory version changes, and keep that assessment with the building case.