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    Don’t Blame it on the Sunshine, Don’t Blame on the Daylight…

    The importance of daylight & sunlight assessments for the construction of new developments.

    Natural light inside buildings is an important element for comfortable living and working. The amount of natural light that a window lets in depends upon the proximity of other buildings or other obstructions.

    Daylight & Sunlight assessments play a crucial role for a planning application. Councils have set ‘BRE daylight and sunlight’ guide as a baseline in order to design buildings that take into account natural light, without shadowing any existing properties or amenities. In some cases these guidelines provide a restrictive basis for the assessment of natural light in high dense areas like London.

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    BRE highlights the importance of natural light levels within proposed, surrounding properties and open spaces in order to provide healthy living environments for all occupants. From our experience and to help avoid objections from third parties and subsequent delays in planning process, our advice to professional property developers and architects, is to really focus on trying to achieve the recommended levels.  However, the planning authorities should judge the significance and acceptability of proposals taking into account all site restrictions.

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    So when is an assessment required for planning purposes?

    A daylight and sunlight assessment is requested when proposed developments are located close to existing properties and can impact their daylight/sunlight levels.

    The 25 degree approach

    When a new building or extension directly faces the affected window, a 25 degree angle is taken from the centre of the lowest window. Suitable daylight for habitable rooms is achieved when the 25 degree angle is kept unobstructed. If the building opposite has a high ridge, the loss of daylight will be noticeable and further calculations will need to be undertaken.

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    Daylight assessment for Code and BREEAM

    Daylight assessment is also important for Code and BREEAM assessments in order to make sure all proposed habitable rooms will receive adequate daylight levels for any future occupants. Credit scores are awarded accordingly.


    New extensions should also be designed to minimise where possible the loss of any daylight and overshadowing of neighbouring properties. It is important to consider carefully the height, distance to boundary, size of plot, orientation and topography. This is where the 45 degree approach should be considered.

    Using this approach, a line is drawn at a 45 degree angle from the centre of the closest ground floor habitable room window of neighbouring properties. The loss of daylight will only be significant if it overshadows more than 50% of the existing window area.

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    Right to light easements

    Another aspect of consideration is the Right to Light. A right to light is a civil matter and is separate from daylight, sunlight and is protected under common law. It is dealt as a parallel process and sometimes it involves the courts depending on the light ‘injury’. Right of light is considered even if the planning permission has been granted.


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