Daylight & Sunlight Assessments for Planning Applications
Daylight and sunlight are material considerations in UK planning decisions. Whether you're developing 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 make confident decisions — and gives your application the strongest possible foundation.
What is a Daylight and Sunlight Assessment?
A daylight and sunlight assessment evaluates how a proposed development will affect natural light — both to neighbouring properties and within the new building itself. Assessments in the UK are guided by BRE Report BR209 (2022), which is widely used by local planning authorities as the benchmark for evaluating daylight and sunlight impacts. For internal daylight within new buildings, BS EN 17037 provides the relevant standard.
The key metrics used in a BR209 assessment include Vertical Sky Component (VSC) and No Sky Line (NSL) for neighbouring properties, and Average Daylight Factor (ADF) and Annual Probable Sunlight Hours (APSH) for new homes and amenity spaces. These indicators allow planning officers, developers, and design teams to assess impact clearly and objectively.
When Do You Need a Daylight or Sunlight Assessment?
A daylight or sunlight assessment is typically required — or strongly advisable — in these situations:
- New residential development or flatted schemes — where the impact on neighbouring properties must be evidenced as part of a planning
- Householder extensions — where a proposed rear or side extension may cross the 45-degree rule and affect a neighbour's
- Internal daylight compliance — demonstrating that new homes meet habitable room daylight targets required by LPA policy or BS EN
- Planning objections or appeals — providing independent evidence to support or challenge a neighbour amenity or daylight concern
What Does a BR209 Assessment Measure?
A full daylight and sunlight assessment covers the following BRE BR209 and BS EN 17037 indicators:
VSC (Vertical Sky Component)
Measures the proportion of sky visible from an existing neighbouring window; the BRE guideline target is 27% or above
NSL (No Sky Line)
Assesses the distribution of daylight within an existing room by mapping which areas of the floor can see the sky
APSH (Annual Probable Sunlight Hours)
Measures sunlight availability to windows and outdoor amenity spaces; windows facing within 90° of due south are tested
ADF (Average Daylight Factor)
Assesses internal daylight quality within new habitable rooms in proposed buildings
Our Specialist Daylight & Sunlight Service
Our dedicated Daylight Sunlight Expert service provides BRE BR209 (2022) and BS EN 17037 compliant assessments for architects, developers, and homeowners across the UK. From pre-application strategy and design advice through to planning submission reports and addendums, our team delivers clear, evidence-based assessments trusted by planning officers and design teams alike. Use our free Daylight Risk Estimator for an instant BR209 scoping check — no registration required.
Speak to Our Team
Unsure whether your project needs a daylight or sunlight assessment, or what scope of report is appropriate? Our consultants are happy to advise. Get in touch today for a no-obligation conversation.