How Many Shading Diagrams Should I Do?

Just how many shading diagrams are necessary to assess the potential shading effects of a spatial design?

Recently a design professional asked me how many shading diagrams were necessary to fully evaluate the extent of potential shading effects. They had provided three diagrams with an application and it had been returned on the basis of requiring further information.

So, how many shading diagrams are enough?
Every case will vary because of the numerous dynamics that need to be considered. The important aspect is to ensure there is enough to appropriately assess that the potential effects are no more than minor.

The method chosen to represent the potential effects will have a significant bearing. If the Shadow Definition Method (SDM) is used, we consider the best rule of thumb is to start with 18 diagrams. This is based on

Three times of the day (i.e. 8am, midday and 5pm).
Three periods of the year (Summer Solstice, Autumn or Spring Equinox and Winter Solstice).
Two comparison options (i.e. the proposal and a complying baseline).
As the sun path on the autumn and spring equinoxes can be roughly equated as the same, the potential shading effects would be similar. Therefore only one set of diagrams is required.

This number may be enough to give a general understanding of the potential effects and could be all that is necessary for the assessment and application. If these indicate potential areas of concern, a greater number of diagrams or more extensive evaluation should be completed.

Shading diagrams are just one factor necessary to provide evidence that the potential effects are no more than minor. A supporting assessment also needs to be submitted. The applicant is responsible for proving that the potential effects are minor. If the application doesn’t include the appropriate information, it cannot be assessed on its true merits.

Shading diagrams and assessments are being requested more often, especially for multi-unit developments and sunlight plane breaches. A clear and accurate assessment of shading and solar dazzle will benefit your application.

If you require specialist shading and/or solar dazzle assessment, feel free to contact us at Sun Study Analysis.