What is the most appropriate time of the year to evaluate the potential effects of shading?

General practice suggests that the most appropriate evaluation period is when there is minimal possible light available i.e. on the winter solstice when the sun’s path is at its lowest and shortest.  Most councils base district plan rules and guidelines on this period with the understanding of it being the worst case scenario.

Guidelines from the United Kingdom recommend the spring or autumn equinox as the most appropriate evaluation period.  This is due to the relative comparisons in the winter solstice being greatly influenced by the lower path in the sky of the sun and bad weather often preventing sunlight occurring during this time.

As yet, there is no clear research defining when is considered appropriate.  District plans may provide guidelines to assist with evaluating a project, but some other things to consider are:

  • How the space is used during the period of the year being assessed.
  • The climatic factors such as rain and cloud which affect the level of sunlight.
  • Surrounding seasonal factors i.e. deciduous trees.
  • The desire for shading to avoid overheating.

If you have any examples or thoughts on the topic, we would greatly appreciate the communication.  If you need assistance with a project, feel free to contact us at Sun Study Analysis.

Are you aware that the phenomenon of solar dazzle can occur from surfaces other than ‘reflective’ surfaces?

The most frequent occurrence of solar dazzle is a result of low sun altitude and a reflective surface i.e. glass facades. However, in certain circumstances solar dazzle can occur from a number of other surface types.

When light radiation hits a relatively smooth surface at an acute angle, the light can be entirely deflected rather than being dispersed in many directions or absorbed. The angle at which this will occur for a given surface can be calculated, which will determine whether or not your building project may cause a solar dazzle effect.

London’s ‘Walkie Talkie’ skyscraper is an extreme case of solar dazzle that has caught media attention around the world. Due to its convex glazed facades it causes areas of intense light radiation that is hot enough to fry an egg. Although total internal reflection is unlikely to last for a period long enough to cause this effect, due consideration should be made during the design stage to avoid these potential effects.

If you are you aware of any buildings that have solar dazzle effects, let us know. If you have any concerns regarding solar dazzle on your project, contact Sun Study Analysis.

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.