There are various methods available for the analysis of sun shading with the results displayed in different ways. These can usually be broken down into two distinctive methods, the Shadow Definition Method (SDM) or the Sun Transit Method (STM).
Each method has advantages and disadvantages. The STM is limited where the assessment involves multiple areas of interest due to freezing the viewpoint. The SDM freezes the time aspect of shading assessment therefore extrapolation of shading data must occur or numerous ‘images’ must be produced which if not represented correctly can make the results difficult to understand.
There are numerous programs available for use which will generate the images or data for the sun analysis. Whichever is chosen will require interpretation to understand the effects that are formed. It is accepted practice to limit the amount of data produced to critical periods of the year. Generally these are the three critical points being the June Solstice, September Equinox and December Solstice. Excluding the influence of Daylight Saving in New Zealand, the March Equinox can be roughly translated to the September Equinox.
Modelling requires assumptions to provide order to the dynamic nature of shading for ease of comparison. The impact of the assumptions should (where possible) be examined to ensure that effects will be no more than those represented in the analysis. Where possible, if an assumption is made that could potentially affect the results, ensure the assumption is applied to each situation i.e. proposal and baseline, to ensure a fair comparison can be made.