Daylight & Sunlight Assessments for Planning Applications
Daylight and sunlight are material considerations in UK planning decisions. Whether you're proposing a new residential scheme, extending an existing property, or responding to a planning objection, a robust daylight and sunlight assessment provides the evidence planning authorities and design teams need to understand potential impacts on natural light — helping support a clear and well-evidenced planning submission.
What is a Daylight and Sunlight Assessment?
A daylight and sunlight assessment evaluates how a proposed development may influence access to natural light — both for neighbouring properties and within the proposed building itself.
In the UK, assessments are typically informed by guidance contained in BRE Report BR209: Site Layout Planning for Daylight and Sunlight, which is widely used by local planning authorities when considering daylight and sunlight impacts on surrounding buildings and amenity spaces.
For internal daylight within new dwellings, assessment approaches may draw on daylight factor guidance historically referenced in BRE publications, or the daylight benchmarks set out in BS EN 17037, depending on local authority policy and the scope of the project.
Importantly, BRE guidance provides recommended benchmarks rather than strict pass–fail rules. Planning authorities typically interpret these guidelines alongside the specific urban context, surrounding built form, and the overall planning merits of a proposal.
When Do You Need a Daylight or Sunlight Assessment?
A daylight or sunlight assessment may be required — or strongly recommended — where a proposed development could influence access to natural light for neighbouring buildings or within new residential accommodation. Common situations include:
- New residential developments or flatted schemes — to demonstrate that surrounding properties will not experience unacceptable reductions in daylight or sunlight, and that proposed homes provide appropriate internal daylight conditions for future occupants
- Householder extensions — where a proposed rear or side extension approaches common planning thresholds such as the 45-degree guideline and could affect daylight reaching neighbouring windows or gardens
- Internal daylight within new homes — where planning policy or design guidance requires demonstration that habitable rooms receive appropriate levels of daylight in line with recognised benchmarks
- Planning objections or appeals — where independent technical analysis is needed to provide objective evidence in response to concerns raised about potential impacts on neighbouring amenity
What Does a BR209 Assessment Measure?
A BR209 assessment considers a range of indicators across neighbouring properties, outdoor spaces, and new homes. Key measures include:
VSC (Vertical Sky Component)
- Measures the proportion of visible sky from the centre of a neighbouring window
- BRE guideline: windows should ideally retain 27% VSC or at least 80% of their former value
- Used to assess potential reductions in daylight to existing properties
NSL (No Sky Line)
- Evaluates the distribution of daylight within an existing room
- Identifies what proportion of the working plane receives direct skylight
- BRE guideline: the area receiving skylight should normally retain at least 80% of its former extent
APSH (Annual Probable Sunlight Hours)
- Assesses sunlight availability to neighbouring windows facing within 90° of due south
- BRE guideline: at least 25% annual sunlight hours, including 5% in winter months
- Or, windows should retain at least 80% of their former sunlight availability
Daylight within Proposed Buildings
- New homes may be assessed using Average Daylight Factor (ADF) benchmarks from BRE guidance
- BS EN 17037 provides an alternative approach using illuminance targets and daylight exposure criteria
- The method used typically depends on project context and local authority expectations
Sunlight to Gardens and Amenity Spaces
- At least 50% of a garden or amenity space should receive a minimum of two hours of sunlight on 21 March
- Development should ideally avoid reducing sunlit area significantly below its former condition
- Applies to private gardens, communal courtyards, and shared outdoor amenity spaces
Our Specialist Daylight & Sunlight Service
Our dedicated Daylight & Sunlight service provides assessments informed by BRE BR209 (2022) guidance and BS EN 17037 daylight benchmarks for architects, developers, and homeowners across the UK.
We support projects from early design feasibility and massing studies through to planning submissions, technical reports, and appeal evidence — helping design teams understand potential daylight and sunlight impacts throughout the design process.
Our assessments consider surrounding buildings, site orientation, and urban context through detailed 3D modelling techniques consistent with BRE methodology, providing clear and transparent analysis for planning authorities and project teams.
You can also use our free Daylight Risk Estimator for an instant BR209 scoping check — no registration required.
Speak to Our Team
Unsure whether your project requires a daylight or sunlight assessment, or what level of analysis may be appropriate? Our consultants are happy to help. Get in touch today for a no-obligation conversation.