Daylight access is an aspect of design that is considered to be crucial by local authorities when assessing a proposed scheme. The standards used to evaluate residential developments at planning stage is the BRE’s Site Layout for Planning Daylight & Sunlight (2011), while non-domestic developments requiring a BREEAM assessment needs to comply with its HEA01 Visual Comfort category daylight access requirements.
So how can architects and engineers ensure that new developments meet the criteria of both assessments? Here are a few key tips to keep in mind to when designing a building –
- Ensure adequate room depths – Design professionals can use the following BRE equation to ensure that room depths are correctly proportioned to allow adequate daylight.
(L/W) + (L/H) < 2/(1-Rb)
Where, L is the room depth (all dimensions in meters)
W is the width of the room
H is the window head height
Rb is the average surface reflectance at the rear half of the room (generally assumed to be 0.5)
- Full height glazing is not necessary – internal daylight calculations are carried out at ‘working height’ in spaces (i.e. 0.85m from floor level in residential buildings and 0.70m in all others) and full height glazing is not necessary to ensure good levels of daylight. If glazing needs to be reduced, do so from the bottom up. Reducing glazing in this manner will also assist in reducing heat losses and the potential for overheating within spaces.
- Locate obstructions, such as balconies, strategically – It is crucial to remember that locating balconies above a window will reduce the amount of daylight being received within a space. It is best to design balconies to be located above circulation spaces, secondary areas and habitable spaces with lower daylight requirements (e.g. retail sales spaces etc.)
- Pay attention to the colour of internal finishes from the onset – As noted in the room depth equation, surface light reflectance does have an impact on daylight calculations, so considering the inclusion of light coloured internal finishes (i.e. wall and ceiling paint, flooring etc.) early on in the design process will have an impact improving daylight results.
- Balance solar control glazing requirements with daylight access – solar control glazing is useful to reduce overheating risks within a space. However, increased solar control usually means reduced visible light access as well. Therefore, it is important to ensure that an overheating risk analysis is carried out alongside a daylight assessment to ensure a good balance is achieved.
GreenBuild Consult carryout daylight assessments for planning and BREEAM. If you would like to talk to us about these services, please get in touch.
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