Modelling for Daylight and Sunlight Assessments - Pager Power
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Modelling for Daylight and Sunlight Assessments

Modelling for Daylight and Sunlight Assessments
May 2, 2024 Harry Watson

Pager Power has developed bespoke software for modelling daylight, sunlight and overshadowing (DSO) effects for building developments. This comes as part of our plans to improve our service offering to our existing client base, and our continual effort to expand and improve our services. The model will produce the results required for Pager Power’s technical team to determine whether a proposed development has an acceptable impact upon the daylight received in accordance with the guidance published by the Buildings Research Establishment (BRE) document 209 [1], and British Standard 17037:2018 [2].

daylight sunlight assessment modelling

Figure 1: Pager Power Skylight Modelling Output. [3]

About the Model

Pager Power has produced a geometric model, which works in a similar way to our existing glint and glare model. It traces rays of light from the sky and the sun to determine the impact of a proposed building development upon available daylight and sunlight for other buildings in the vicinity and to determine its own daylight and sunlight availability. It does this by considering the effects of overshadowing on access to skylight and sunlight from nearby windows. Pager Power has considerable expertise in modelling the movement of the Sun and a deep understanding of how this pertains to complex and specialised planning issues, having delivered over 1,300 solar glint and glare assessments worldwide. This expertise, combined with our in-house development capabilities, has allowed us to develop a world-class model for daylight, sunlight and overshadowing with outputs tailored to the requirements set out in BRE 209.


The position of the Sun is considered alongside the dimensions of the existing and proposed developments and the position of their windows. It currently uses the skylight and sunlight indicators contained in Appendix A of BRE 209 as a basis for the calculations and modelling results. The model has been optimised to handle a variety of inputs and, as with all of Pager Power’s bespoke software, is easily customizable for maximum versatility when producing an output to meet your particular planning needs. Additional features have already been developed which allow Pager Power to analyse overshadowing of outdoor spaces.


Daylight, Sunlight and Overshadowing assessments will have results presented visually in the form of skylight and sunlight indicators, with more detailed tabulated results. The results outline the Visual Sky Component (VSC) and Annual Probable Sunlight Hours (APSH) respectively for each window in the proposed development and nearby surrounding buildings. Finally, all results are considered alongside one another to determine whether they are acceptable in accordance with BRE 209 [1]. 

About Pager Power

Pager Power is a dedicated technical consultancy that has been providing independent guidance and advice regarding solar developments, wind farms, and building developments internationally since 2002. Further details about what we services we can provide can be found here. Pager Power has completed over 1,300 glint and glare assessments, over 1,000 aviation/radar impact assessments, over 500 television and radio reception surveys, and over 500 telecommunications impact assessments.

If you require a daylight, sunlight, and overshadowing assessment then please contact us here.


[1] BRE 209

[2] BS EN 17037:2018

[3] Pager Power modelling output


Thumbnail image accreditation: Nadine Shabaana (2016) on Last accessed on 01.05.2024. Available at:


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