Part O Overheating

Part O Overheating Assessments for New Residential Buildings

Crowther Solutions provides Part O overheating assessments for new residential buildings in England, using either the Simplified Method or Dynamic Thermal Modelling where appropriate. Approved Document O is intended to limit unwanted solar gains and provide adequate means of removing excess heat, helping demonstrate compliance with the overheating requirements of the Building Regulations.

Our Part O Assessment Methods

1. The Simplified Method

The Simplified Method provides a straightforward Pass or Fail assessment against the limits set out in Approved Document O. It is primarily driven by glazing areas and the amount of openable area available for removing excess heat, together with factors such as location, orientation and cross-ventilation.

Because the method uses prescribed limits, there is relatively little flexibility if the proposal fails. In many cases the practical options are to reduce glazing areas, increase the available openable area, or revise the proposed design so that it falls within the simplified criteria.

2. Dynamic Thermal Modelling

Dynamic Thermal Modelling provides a much more detailed assessment of how the dwelling is likely to perform during periods of hot weather. Rather than relying solely on prescribed glazing and opening limits, the model can take account of the actual building geometry, construction, window g-values, external shading and overhangs, ventilation strategy and other overheating mitigation measures.

This can be particularly useful where large areas of glazing are an important part of the design. If the Simplified Method would require smaller windows or larger openings, Dynamic Thermal Modelling may allow alternative measures such as solar-control glazing, external shading or, where appropriate, mechanical cooling to be assessed instead.

Where a project does not initially meet the required criteria, we can model alternative options provided by the project team and show how they affect the overheating assessment.

Part O assessments are undertaken to demonstrate compliance with the overheating requirements of the Building Regulations using the criteria set out in Approved Document O. The assessment helps identify and reduce the risk of overheating, but it cannot guarantee that a completed building will never overheat in use, as actual performance can be affected by weather conditions, occupant behaviour, ventilation use and the final construction.

Practical Part O Compliance Support

Crowther Solutions can support both the SAP assessment and Part O overheating assessment for the same project, helping ensure the information used across both assessments remains consistent. Factors such as window sizes, glazing g-values, U-values, shading and ventilation can influence the results of both assessments, so changes made to improve one area may need to be considered against the other.

By dealing with both assessments, we can highlight where proposed changes may affect SAP performance or Part O compliance and provide clear technical guidance to the project team. The final design and specification remain the responsibility of the appointed designer.

Request a Part O Assessment Quote

Send us your project information and we’ll review the assessment requirements and provide a project-specific quotation.

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