Lighting Assessment for Residential Development Near Woodland Habitat
Southwest Environmental Limited was recently instructed by an architectural firm to produce a Lighting Assessment for a proposed residential development. The site is located in Buckland Ripers, Dorset, and falls within the planning jurisdiction of Dorset Council.
The Development
The proposed development comprises the construction of a single residential dwelling, a garage, and an associated garden. Environmental constraints were a primary consideration for this site. The location is situated 1.6 kilometres from the Dorset National Landscape Area of Outstanding Natural Beauty (AONB). Furthermore, a woodland area is located just over 20 metres to the south of the proposed dwelling. Ecological surveys previously conducted at the site identified the presence of Myotis bats within this woodland. Myotis bats are known to be highly sensitive to artificial light, necessitating careful planning and mitigation.
Objectives
The objective of our Lighting Assessment was to design a lighting scheme that meets the safety and operational requirements of the future human occupants while preventing light spill that could negatively impact the adjacent bat habitat. The assessment was conducted in accordance with relevant legislation, including the Planning (Clean Neighbourhoods and Environment) Act 2005, and national planning policies which require new developments to limit the impact of light pollution on nature conservation.
To achieve the necessary control over light emission, we developed a strategy adhering to the guidelines set out by the Institute of Lighting Professionals and the Bat Conservation Trust. External lighting is restricted to narrow-beam, horizontal cut-off LED downlighters mounted at low elevations, specifically 0.6 metres and 1.6 metres above ground level. These luminaires will be fitted with passive infrared (PIR) and dawn-to-dusk sensors to ensure they are only active when required. We specified a warm colour temperature range of 2700k to 3000k to minimise the ultraviolet light output, which is known to attract insects and disrupt bat foraging patterns. Up-lighting was strictly prohibited across the entire site.
A Well Lit Space
Internal light spill was also evaluated as a critical factor due to the proximity of the southern woodland. To address this, the design incorporates electrochromic glass on the windows of the front entrance. This dynamic glazing activates when internal lighting is switched on, providing up to a 90 percent reduction in visible light transmission through the glass.
Method & Outcome
We utilised lighting design software to model the proposed external and internal lighting, producing lux contour plans for both horizontal and vertical planes. The quantitative analysis demonstrated that horizontal light spill on the ground would remain below 0.5 lux around the immediate development, dropping below 0.2 lux well before reaching the woodland edge. Vertical luminance along the woodland boundary was also shown to be predominantly below 0.2 lux, ensuring the bat habitat remains sufficiently dark. Construction phase mitigation measures were also detailed to prevent temporary light spill during the build.
This comprehensive analysis and the accompanying mitigation strategy were completed with a short lead time to assist the client in maintaining their planning submission schedule.
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