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Daylight and Sunlight Assessment

Daylight and Sunlight Assessments are often also known as ‘Daylight, Sunlight and Overshadowing Assessments’ or as ‘Right to Light Studies’. Daylight and Sunlight assessments are used to demonstrate the impact of a development on neighbouring properties and the daylight access within a proposed design. 

Daylight and Sunlight studies are carried out in order to determine the potential for natural light to enter a room in line with the criteria set within the BRE’s ‘Site Layout Planning for Daylight and Sunlight’, but also can be required for either BREEAM or as a planning condition. If you are thinking of a building a new domestic dwelling in London, or simply looking to add an extension onto an existing property, there is a big chance that your local planning authority will ask for a Daylight and Sunlight Assessment. Usually, it needs to be carried out and submitted as a part of your planning documents.

QuinnRoss Energy can provide the calculations and expert analysis required in order to help secure your planning permission.

We all know that a good access to daylight and sunlight is a vital part of a healthy environment. The efficient utilisation of daylight in a property will reduce its dependence on artificial lighting, thereby enhancing its energy performance and environmental credentials. Carefully considered design can help mitigate the impact on surrounding areas, whilst maximizing the development potential of a site and the delivery of good quality daylight & sunlight for future occupiers. The sensitive design should provide sufficient daylight and sunlight to new housing while not obstructing light to existing homes nearby.

The BRE Report, Site layout planning for daylight and sunlight: a guide to good practice (BR209), advises on planning developments for good access to daylight and sunlight, and is widely used by local authorities during planning permission to help determine the impacts of new developments.

A BRE Daylight and Sunlight report will typically contain the following tests:

  • Vertical Sky Component (VSC) analysis for daylight access
  • Daylight Distribution/No Sky Line
  • Average Daylight Factor (where BRE Appendix F criteria applies)
  • Annual and winter probable sunlight hour calculations 
  • Overshadowing to Gardens and Open Spaces
  • Annual Probable Sunlight Hours (depending on the orientation)
  • Façade analysis for daylight and sunlight access
  • Room Depth (if required)

At QuinnRoss Energy we review relevant planning requirements of local authorities prior to undertaking our calculations, ensuring that the most appropriate analysis is undertaken for your design. We are also Right to Light surveyors and therefore carry out assessments for the common law Right to Light.

Modelling takes into account all the factors that are essential in providing accurate results, such as orientation, geometry, location, surrounding buildings and even vegetation. Accompanied by clear and concise reports.

What is a daylight and sunlight assessment?

This assessment is a 3D modelling and simulation exercise, where the majority of the time we assess the amount of daylight and sunlight an existing building receives when a proposed development is in place. This is done through analysing facades of structures for their Vertical Sky Component (VSC) calculations, that assesses daylight, and Annual Probable Sunlight Hours (APSH), that assess sunlight. If more details are known then internal spaces can be analysed for their internal Average Daylight Factor (ADF), which is a more detailed variant of daylight assessment.

Is it that significant an issue?

Yes, very. Daylight and sunlight are actually legal requirements and a very sensitive issue when it comes to development. All people have a right to light, it’s a legal obligation, and if a proposed building obscures daylight and sunlight it is unlawful and will almost certainly be rejected at planning.

How do you do an assessment?

We build a 3D block model of the existing surrounding area, including all adjacent houses and structures and simulate the amount of daylight and sunlight their facades receive. We then insert the proposed development, as a 3D model, run the calculations again and compare the two results. The Building Research Establishment (BRE) provides guidance on acceptable levels of daylight and sunlight which is the criteria the industry uses for compliance.

Need Help With Your Project?

Contact one of our energy assessors today on 01795 845 780, or email us at hello@quinnross.energy


RIBA stages

When do I need Daylight and Sunlight Assessment?

Services for RIBA 0 - 7

Whether you need a SAP for a bungalow, or overheating analysis for a penthouse, our technical specialists will work with you to find the best solutions for compliance within your deadlines and budget, explaining them in plain English.