Guidance · 4 min
When should Part O be considered during design?
Why overheating should be tested before elevations and opening strategies are fixed.
Earlier than most projects expect
Consider overheating when orientation, glazing proportions, external shading and opening arrangements are still being developed. These decisions are difficult to revisit once planning elevations or supplier packages are fixed.
Coordinate the constraints
A large opening is not automatically usable for purge ventilation. The design may need to account for noise, security, guarding and practical operation, depending on the situation.
Review alongside energy strategy
Measures that reduce heat loss or increase solar gain can affect summer performance. Part L, Part F and Part O should therefore be coordinated rather than treated as isolated reports.
What to send
Plans, elevations, sections, site orientation, window schedules and information about external constraints are a useful starting point.
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.