Southwest Environmental Limited

London Sunlight & Daylight Assessments

Are you bringing forward a development in a densely populated area of London or the Greater London boroughs? At Southwest Environmental Limited, our London office provides highly accurate Sunlight & Daylight Assessments. Using advanced 3D modelling, we ensure your scheme satisfies local planning authorities by adhering to the Building Research Establishment (BRE) guidelines (BRE 209: Site Layout Planning for Daylight and Sunlight, updated to BS EN 17037 standards).

We typically break our assessments down into two distinct categories depending on the requirements of your Local Planning Authority (LPA):

1. Impact on Existing Buildings (Neighbouring Properties)

When developing in tight urban spaces such as Camden, Islington, or central London, a primary concern is whether your new building will cast unacceptable shadows over existing homes. A Daylight Impact Assessment (often colloquially linked to "Right to Light") calculates the reduction in light to neighbouring windows.

• Vertical Sky Component (VSC): We calculate the amount of skylight falling on a vertical wall or window. A VSC of 27% or more is considered good, while reductions exceeding 20% of their former value can trigger objections.
• Annual Probable Sunlight Hours (APSH): We measure the sunlight reaching neighbouring south-facing windows to ensure they receive adequate winter and year-round sun.
• Overshadowing to Gardens & Open Spaces: We map the path of the sun to ensure existing private amenities and public parks maintain at least two hours of sunlight over 50% of their area on March 21st.

2. Adequacy of Lighting Within New Developments

It is equally critical that the rooms within your proposed development receive sufficient natural light, promoting the health and well-being of future occupants. Local policies increasingly demand proof of internal daylight quality before granting permission. We conduct an Internal Daylight Assessment utilizing the latest Climate Based Daylight Modelling (CBDM) and standard tests.

• Target Illuminance & ADF: Used to calculate the average interior illuminance of a room compared to the unobstructed outside illuminance (e.g., assessing daylight autonomy targets against local climatic data).
• Spatial Daylight Autonomy (sDA) / No Sky Line (NSL): Evaluates daylight distribution and whether a room receives enough daylight during standard operating hours over the course of a full year.
• Overheating Mitigation: In line with the London Plan and the GLA's Net Zero targets, we balance solar gain for natural light against the risk of summer overheating, ensuring optimal facade and window orientations.

Why Choose Our London Team?

Operating from our London office, we have extensive experience dealing with the specific urban density and architectural challenges of Greater London. Whether you are dealing with a restrictive infill plot or a large-scale regeneration project, we provide detailed, visual reports that clearly demonstrate compliance to planners.

Contact our London Office today on 02076 920 670 or email london@southwest-environmental.co.uk to discuss your Sunlight and Daylight modelling needs.

Example Projects & Local Technical Insights

Below are recent projects and technical updates from our weblog directly relating to lighting, sustainable building, and solar gain in the London region:

• New Net Zero Housing Policy in London: An overview of the London Plan, exploring how balancing natural sunlight and solar gain is crucial for minimizing energy demands while satisfying new climate resilience and overheating policies.
• Daylight Impact Assessment for Urban Infill – London: A case study demonstrating how we used 3D VSC modelling to prove a proposed apartment block would not unacceptably overshadow neighbouring terraced properties.
• Understanding Light Pollution & Reflected Glare: A technical breakdown of how sunlight reflected off modern glass facades in urban environments can cause severe glare for road users, and how careful design can mitigate it.
• Internal Adequacy & Daylight Modelling – London Boroughs: Detailing our approach to balancing strict heritage constraints with the need for modern daylighting standards in newly converted living spaces.

What Our London Clients Say