Guidance · 5 min
What is a Part O overheating assessment?
The purpose of Part O and the design decisions that commonly affect overheating risk.
What Part O addresses
Part O of the Building Regulations addresses overheating risk in new residential buildings in England. Approved Document O provides guidance, but the appropriate assessment route and inputs depend on the scheme.
What affects the assessment
Glazing area and orientation, shading, openings, purge ventilation and the ability to use openings safely can all be relevant. Noise, security, pollution and fall risk may constrain otherwise obvious ventilation strategies.
Assessment routes
Approved Document O provides more than one route. Not every scheme should be assessed in the same way, and a project may need more detailed analysis depending on its form, location or constraints.
The useful outcome
The assessment should produce coordinated design information: not simply a pass/fail statement, but a clear understanding of any required glazing, shading or ventilation measures.
Building Regulations guidance and assessment methods can change, and transitional provisions may apply. Confirm the correct route for the particular project rather than relying on a general article.