Wave Dynamics GuidesLight Spill and Obtrusive Light Explained
How light spill and obtrusive lighting are assessed for planning, including ILP Guidance Note 01, environmental zones, sky glow and lighting near bat habitats.
In Short
A light spill or obtrusive light assessment checks whether external lighting from a development, such as floodlights, car parks, signage or building lighting, will shine into nearby homes, cause glare or sky glow, or disturb wildlife such as bats. It compares predicted light levels with recognised guidance and recommends design changes where needed.
- Uses the Institution of Lighting Professionals (ILP) guidance on obtrusive light.
- Limits depend on the environmental zone, from dark landscapes to city centres.
- Considers light into windows, glare, upward light and sky glow.
- Lighting near bat habitats follows specific ecological guidance.
When Is It Needed?
Planning authorities ask for lighting assessments for sports pitches, floodlit facilities, logistics yards, car parks, data centres and developments next to homes or sensitive habitats. Ecologists often need lighting contour plans to show that bat commuting and foraging routes stay dark.
Environmental Zones
ILP Guidance Note 01 groups locations into environmental zones, from E0 (protected dark landscapes) to E4 (high district brightness such as city centres). Each zone has limits for light into windows, luminous intensity of fittings, upward light and building luminance, with stricter values after a curfew time.
How It Is Assessed
Lighting is modelled in 3D using the proposed fittings, mounting heights and aiming angles. Results are shown as contour plans and as illuminance at receptor windows, and compared with the limits for the zone. Baseline light surveys can record existing conditions.
Good Lighting Design
- Use fully shielded fittings with no upward light.
- Aim lights down and away from boundaries.
- Use warmer colour temperatures near wildlife.
- Use controls, dimming and curfews outside operating hours.
Frequently Asked Questions
Can Wave Dynamics carry out light surveys after construction?
Yes. We carry out baseline, construction and post-construction light monitoring surveys to confirm lighting complies with planning conditions.
Why does lighting affect bats?
Many bat species avoid lit areas, so lighting can block commuting routes and foraging areas. Ecological guidance sets out how to design lighting that keeps key areas dark.
This guide gives general information and is not a substitute for project-specific advice. Requirements change, so always check the current regulations, guidance and your planning conditions. Ask our team about your project.
Jon Maguire (BSc Hons MIOA) brings over 8 years of expertise in acoustic consultancy, specialising in environmental acoustics with a focus on 3D modelling, assessments, and detailed design for industrial, commercial, and energy projects. He has lead noise assessments for key clients while thriving in multidisciplinary environments. Jon’s diplomatic communication skills are ideal for stakeholder consultation.
Jack is a Field Engineer at Wave Dynamics, supporting the delivery of environmental monitoring and acoustic consultancy services through detailed on-site fieldwork. He has hands-on experience in noise monitoring, vibration monitoring, and dust monitoring across a variety of infrastructure, construction, and environmental projects. Jack is involved in the setup, operation, and maintenance of monitoring equipment, ensuring accurate data collection in line with relevant standards and project requirements. He works closely with consultants and project teams, providing reliable field support that underpins high-quality assessments and reporting.
Aidan is the Director for all U.K Operations and has worked in multiple industries including for clients in the UK and internationally operating in the residential, industry, healthcare, education, and construction sectors.
