Understanding BRE 209 (2022): The Latest Daylight and Sunlight Guidance

For architects, developers, and planners in England and Wales, daylight and sunlight access has never been more critical in the design and assessment of buildings. With growing pressure to optimise land use, increase housing density, and achieve net zero targets, understanding the latest BRE 209 guidance is essential.

BRE 209 (2022) – Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice – provides updated best practice for assessing daylight and sunlight in and around buildings. This latest edition supersedes the 2011 version and aligns closely with BS EN 17037, the European Standard on daylight in buildings.

This article provides a clear and comprehensive breakdown of BRE 209 (2022), what’s changed, and how professionals should apply it across design, planning, and environmental impact assessments.

Understanding BRE 209 - What is it?

BRE 209 (2022) is a non-statutory guidance document published by the Building Research Establishment (BRE). It outlines how to plan and design developments that respect daylight and sunlight access — both for the proposed scheme and for surrounding existing or future buildings.

It is intended to support the British Standard BS EN 17037, which focuses on interior daylighting. BRE 209 complements this by guiding site layout and massing decisions to optimise daylight availability and protect amenity.

Key Principles of BRE 209 (2022)

1. Purpose

Promote good daylight and sunlight access to new buildings and open spaces.

Safeguard existing buildings from unacceptable loss of light.

Protect development potential of adjoining land.

Inform Environmental Impact Assessments (EIA) and local planning policies.

2. Status

BRE 209 is not legally binding or part of national planning policy. However, it is widely adopted by local authorities as a material consideration, particularly for major developments, urban infill, and tall buildings.

3. Flexibility

Numerical values in the guide are not absolute standards. They can be varied to suit urban context, architectural ambition, or where meeting the guidance would unduly constrain good design (e.g. conservation areas, city centres).

Core Assessment Areas

BRE 209 (2022) sets out detailed methodologies for assessing three key areas:

1. Light from the Sky – Daylight

Assessed through:

Vertical Sky Component (VSC): Measures how much sky is visible from a window.

Daylight Distribution (No Sky Line - NSL): Maps areas in a room where the sky is visible.

Daylight Factor or Illuminance: Based on BS EN 17037 metrics for internal light levels.

Key thresholds:

VSC ≥ 27% usually ensures good daylight.

NSL reduction to less than 80% of original value may be noticeable.

Daylight Factor targets vary by location and room use (e.g. 1.5% for living rooms in London).

2. Sunlight

Sunlight is assessed for windows facing within 90° of due south using:

Annual Probable Sunlight Hours (APSH): A metric reflecting typical sunlight received at a point over the year, adjusted for weather.

Key thresholds:

At least 25% APSH, including 5% in winter, is desirable.

A drop to less than 0.8 times the previous value is typically noticeable.

Sunlight to gardens and amenity space should provide 2+ hours on at least half the area on March 21.

3. Impact on Adjoining Land

New development should not hinder the potential of adjacent sites to receive adequate light.

A 43° angle from 1.6m above ground at the boundary is used as a test for daylight potential.

What's New in the 2022 Edition?

BRE 209 (2022) introduces several important updates:

🔹 Alignment with BS EN 17037

The guidance now references target illuminance values and daylight factors based on climate data, replacing older Average Daylight Factor methods.

🔹 Refined Methodologies

The VSC test remains, but greater emphasis is placed on distribution of daylight within a room (no sky line) and contextual interpretation of results.

🔹 Consideration of Trees and Future Development

Appendix G details when and how to include trees and hedges in calculations. Adjacent land's development potential must be respected.

🔹 Greater Flexibility and Context Sensitivity

Section 5 encourages interpreting daylight and sunlight not in isolation, but alongside design quality, privacy, views, enclosure, microclimate, and site constraints.

🔹 Enhanced Tools

Appendices A–C provide updated methods for calculating VSC, sunlight hours, and daylight factors using modern software or Waldram diagrams.

Best Practice Tips for Practitioners

Start Early
Incorporate daylight and sunlight testing in early feasibility and massing studies, not just during planning submission.

Model in 3D
Use climate-based daylight modelling (CBDM) tools to assess spatial daylight autonomy and daylight uniformity for internal spaces.

Communicate Clearly
Use visuals like VSC heat maps, no sky line diagrams, and shadow studies to support planning submissions and consultations.

Justify Deviations
If strict compliance isn't possible (e.g. in dense urban settings), justify your approach with qualitative assessments and context analysis.

Combine with Overheating and Glare Analysis
High daylight levels can increase overheating risk. Reference CIBSE TM59 or TM52 where relevant.

Real-World Applications

BRE 209 is critical in assessing:

Urban infill schemes: Ensuring minimal impact on neighbouring daylight and sunlight while optimising site density.

Tall buildings: Evaluating overshadowing and wind effects on surrounding public realm and gardens.

Conversions: Assessing whether existing windows will retain adequate light.

Planning objections: Providing evidence in rights to light disputes or neighbour consultations.

Frequently Asked Questions - Understanding BRE 209

What is the Vertical Sky Component (VSC)?

VSC measures the amount of sky visible at the centre of a window. A value above 27% is usually associated with good daylight.

Is BRE 209 (2022) mandatory?

No. It is guidance only, but widely used by planning officers and often forms the basis of planning conditions.

What’s the difference between BRE 209 and BS EN 17037?

BRE 209 deals with external layout and impact on neighbouring sites. BS EN 17037 focuses on internal daylight levels.

How does BRE 209 apply to Rights to Light?

While related, BRE 209 is separate from legal rights to light assessments, which are based on civil law and may use different methodologies.

Can trees be included in assessments?

Yes. BRE 209 (2022) Appendix G offers guidance on when and how to factor in trees and hedges — typically for winter evergreen species or formal rows of trees.

What is the 25° and 43° rule?

These angles are used to assess whether new development is likely to significantly impact the daylight potential of neighbouring buildings (25°) or adjacent development sites (43°).

Final Thoughts - Understanding BRE 209

BRE 209 (2022) sets a national benchmark for daylight and sunlight considerations in planning. While flexible in interpretation, it encourages consistency, fairness, and good design — balancing density and liveability.

Architects, planners, and developers must now integrate this guidance into early design decisions and provide robust technical assessments where daylight and sunlight are affected.

Need Help with BRE 209 Daylight & Sunlight Assessments?

At Anstey Horne, we are specialists in daylight and sunlight assessments. Whether you’re preparing a planning application, defending against objections, or reviewing your development potential, our team can help.

For more advice on how we can help support a planning application with a daylight & sunlight assessments please give us a call. If you would rather we contacted you please fill in our Contact Form and we will be in touch.

For more information on understanding all aspects of BRE 209 Daylight & Sunlight Assessments for planning see the collection of articles on our blog page.

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