Daylight and Sunlight Assessments

Stroma Tech’s Daylight and Sunlight Assessments can assist with maximising the use of natural light to enhance building energy performance, environmental quality and user comfort.

Whether you are a developer, designer or local authority, daylight and sunlight calculations can assess the impact of natural light and potential environmental effects a development may cause.

We offer the following services in accordance with BRE 209 – ‘Site Layout Planning for Daylight and Sunlight’, which takes into account site features, obstructions and topography:

  • Daylight and Sunlight Assessments for planning applications
  • Average Daylight Factor Assessment
  • Overshadowing Assessments (Vertical Sky Component)
  • Annual Probable Sunlight Hours (APSH)
  • Daylight Calculations for BREEAM and Code for Sustainable Homes
  • Maximum Envelope Calculations

Assessments for Planning applications

Recently, daylight and sunlight factors are now being taken into account when determining applications for proposed schemes. Increasingly, local planning authorities are now considering the impacts as material planning considerations.

The assessments can be used to improve the overall design of a development, ensuring adequate levels of natural light are present, and can be used to meet requirements set out in planning applications.

We can also assist designers to control solar heat gain and achieve sufficient light levels, in compliance with their responsibilities under Part L of the Building Regulations.


Using specialist modelling software, Stroma Tech provides daylight and sunlight calculations for existing, adjoining and proposed developments, including full reports, inclusive of the approach taken, results and assessment conclusions.

Daylight Assessments

Stroma Tech can undertake photometric simulations to determine both daylight factors and uniformity factors (daylight distribution analysis).

Daylight simulation is particularly useful in non-residential buildings, which includes complex building geometry or roof lights, and where the usual Part L2a compliance process would other be unable to determine average daylight factors.

Average Daylight Factor

If required, Average Daylight Factors (ADF) can be carried out through the reported VCS values and is intended to highlight where adequate levels of daylight should be attainable. ADF values are available for existing buildings if the relevant drawings are made available.

Overshadowing Assessments (Vertical Sky Component)

We can provide calculations for the Vertical Sky Component to assess the impact of a new development on the availability of daylight to neighbouring structures – often a requirement for planning applications. Overshadowing assessments for basements and amenity areas are also available.


Annual Probable Sunlight Hours

Our Annual Probable Sunlight Hours (APSH) calculations provides the amount of sunlight a given window may expect over a year period, covering amenity areas and ground floor unobscured windows of surrounding dwellings.


If your development is working towards an environmental assessment method, our daylight calculations and reports can help to achieve a required rating through the following credits:

  • BREEAM Hea 01 Visual comfort – Daylighting
  • Code for Sustainable Homes HEA1 Daylight

Each report is carried out to support BREEAM and CODE projects, and can also be produced to support a planning application.


In the early stages of planning, we can assist in providing analysis of the maximum building envelope size to help developers determine how much space they can utilise, without restricting natural light to neighbouring buildings.

Request a quote for Daylight & Sunlight assessments on your project by calling 0845 621 22 22, emailing or completing our Quick Contact Form


Here you will find some of our case studies.
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Part of the Stroma Group
Titanic Belfast, The Signature Building
Phil Carr