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England only

Part O simplified-method screening

A free interactive worksheet for exploring selected inputs and limits in Approved Document O (Overheating), 2021 edition.

Approved Document O applies to relevant new residential buildings in England, not later extensions or changes of use. This worksheet is designed for a dwellinghouse or individual residential unit; shared communal, common and institutional spaces need separate competent assessment. It is not a formal compliance report, does not replace the Approved Document O compliance checklist and does not establish that the simplified method is suitable for a project.

Where the route changes: external noise, pollution, security, fall-protection constraints, communal distribution pipework, unusual geometry or values outside the entered limits may require dynamic thermal modelling or other project-specific evidence.

The tool uses conservative route, completeness and consistency gates. An incomplete or uncertain schedule cannot produce a positive screening outcome.

Your entries stay on this device and are used to create your saved input file or screening worksheet. Briary records only privacy-minimised, pseudonymous tool events; no project fields are sent. Clear the tool after use on a shared device.

Project details
Simplified method inputs
Permitted measures: ventilated external shutters; glazing with g-value ≤ 0.4 and light transmittance ≥ 0.7; or a 50° altitude-cut-off overhang on a due-south façade only.
Use the help buttons for definitions and what to enter. The tool uses a discharge coefficient method to convert opening geometry into equivalent area.
Route and completeness checks Required before a positive outcome
“Not sure” stops a positive outcome and identifies the point that needs competent review. For High Risk shading, use the help button to check the permitted measures.
Window and door data
Add one row per physical opening or fixed glazing component. For an openable sash with several panes, enter their combined transparent area once on the sash row so its equivalent area is not duplicated. Only rows marked as opened for removal of excess heat count towards the ventilation check.
Bedroom night ventilation only counts where the opening can be left safely open overnight. If a bedroom window is easily accessible and not secure, the night-time equivalent area will be zero. Restrictor entries affect this numerical screen only; they do not verify guarding, protection from falling or entrapment, handle reach, security hardware or usability.
Results breakdown
How to read this. “Within” and “outside” compare only the entered values with the selected simplified-method limits. The overall screening outcome also checks route suitability, schedule completeness and bedroom coverage. It is never a formal compliance decision.

Key context

Largest glazed façade orientation
N/A
Total floor area used in calculation (m²)
0
Most glazed room, by % of its floor area
N/A
Total glazing area (m²)
0

Limiting solar gains

Check Actual Target Result
Total glazing, % of floor area 0% 0% N/A
Most glazed room, % of room floor area 0% 0% N/A
High-risk shading confirmation N/A N/A N/A

Removal of excess heat, purge ventilation

Check Actual Target Result
Total equivalent area, % of floor area 0% 0% N/A
Total equivalent area, % of glazing area 0% 0% N/A
Total equivalent area (m²) 0 - N/A

Bedrooms and sleeping rooms, night-time ventilation

Need a formal output? Send the drawings, window schedule and known opening constraints to Briary. We will confirm whether the simplified route is suitable or whether dynamic thermal modelling should be scoped.
This screening tool is provided as-is with no warranty. It is not a formal compliance report or the Approved Document O compliance checklist. A competent person must verify the route, inputs, safety and usability constraints, calculations and evidence for the project.