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22 June 2020

Factors to Consider When Analysing Additional Shading

shadow house

Shading diagrams are just the first step when it comes to considering additional shading created by a project. Once you have these, it's important to analyse the additional shading in order to determine whether it will be considered 'more than minor'. Several factors come into play here, including the use of the shaded area, district plan rules, the NZBC and the characteristics of the specific site. In today's blog post, I've outlined these factors and how they may influence different projects. 

The use of an area

The use of an area must be considered when assessing the potential impact of shading. If shade were to occur onto a commercial or industrial property, it is accepted as of lesser importance than the same shadow on a residential area. This is mainly due to the nature of the use which occurs within that area.

As an example, if a proposal was to shade the adjoining property’s garage this would be considered to have a lesser effect than if the same shadow was cast on a living area. As different uses may benefit from sunlight during different times of the day, this further emphasises the necessity to evaluate each situation individually.

An effective way to extrapolate the information formed is to divide the subject site/s into distinctive areas with particular uses. When a proposal and a baseline are considered within these defined areas, it will give a fair comparison of the change in shading effects.

District plan rules

District Plan rules are written to provide a set of general instruments that relate to the objectives and policies. If a building can be constructed in accordance with these rules, this building, excluding the requirements of the Building Act, can be constructed as of right. In relation to shading and sunlight, these rules are not a guarantee that sunlight will be available for all hours of the day for all periods of the year. Often conflicts arise due to applying a general rule to a specific situation.

Take for an example a subject site located on a steep hill site which adjoins residential sites with existing dwellings to the south. The general rules for protection of sunlight for the lower properties mean that anything larger than a cardboard box would be deemed to not comply.

The possible solution is to provide clear and concise information to the adjoining neighbour to attempt resolving their fears. This potential eliminates the need for a limited notified or fully notified Resource Consent application. In order to supply the necessary information, modelling of the proposal and relevant surrounding topography and structures is required.

The extent of modelling for the surrounding must be determined by the nature of the Shading Analysis required on a case by case basis. There is little point in including the surrounding topography i.e. hills to the east if the area of concern is the setting sun.

New Zealand Building Code

The importance of access to natural light is further highlighted by the inclusion of the New Zealand Building Code Clause G7: Natural Light.

The objective G7.1 states: “The objective of this provision is to safeguard people from illness or loss of amenity due to isolation from natural light…..”

Although the New Zealand Building Code does not specifically relate to the Resource Management Act, the principle that occupants of buildings require adequate access to natural light to enhance the possibility of remaining healthy is the same.

Site characteristics

The location of the subject site and local and regional factors can greatly influence the results of a sun analysis.

Such factors include the location of the surrounding hills which will alter the effective sunrise time. An example would be the difference of sunrise when on the ocean where the horizon is Mean Sea Level (MSL) compared to the location on the west side of Mount Victoria where the horizon is 196 metres above sea level.

Currently, the majority of environmental case law suggests the no account be made for existing trees. Trees provide a number of functions to the environment including privacy and shading. Trees generally have fewer restrictions imposed upon them than the built environment in relation to District Plan requirements. Therefore they should not be modelled due to the potential for removal.

Although not modelled, the amount, type and volume of existing trees if any, will mitigate any potential shading. It is suggested that trees add to the vitality and enjoyment of neighbourhoods and retention of trees is largely endorsed by society.

The team at Sun Study Analysis have in-depth knowledge and considerable experience working with Council rules, District Plan rules, the NZBC and the Consent process. Their services range from basic design evaluations to in-depth studies for presentation at a Notified Resource Consent hearing.

If you need assistance with a project, feel free to contact Gavin Barber on or 04 569 6109 or visit the Sun Study Analysis website.

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