Lighting assessments and who should prepare one
There is no protected title for lighting assessment, so councils look at membership, method and whether the author can justify the environmental zone they applied.
The lighting assessment author a council will accept is someone who can demonstrate competence against the Institution of Lighting Professionals guidance on reducing obtrusive light, usually a lighting designer or engineer with ILP membership. There is no statutory licence for this work and no protected title, which is precisely why councils scrutinise who signed the report. If your car park, forecourt or external plant lighting has attracted a condition, the officer wants calculated results from someone who understands the difference between designing a lighting scheme and assessing its spill.
Most small commercial applicants discover this late, when a condition requires a lighting scheme to be approved before first use and the electrical contractor's product sheet is not enough.
What an obtrusive light assessment measures
Four things, and they are separate calculations rather than one number.
Sky glow, which is the light escaping upwards and brightening the night sky. Light intrusion into windows of nearby dwellings, measured as vertical illuminance on the window plane. Luminaire intensity towards an observer, which governs glare. And building or sign luminance, which matters for illuminated fascias and floodlit elevations.
An assessment reports each against the limits for the relevant environmental zone, before and after a curfew time. It should also identify every sensitive receptor by address or reference, show the calculation grid, and state the assumptions: mounting heights, tilt angles, luminaire types, photometric files and maintenance factor.
A drawing showing lamp positions is not an assessment. Neither is a manufacturer's lux plot of the site with no receptors on it.
The environmental zones and how they are chosen
The ILP guidance divides the country into zones running from intrinsically dark areas, through dark rural and low-brightness village settings, to medium-brightness suburban locations and high-brightness town and city centres. The limits tighten sharply as you move down the scale, so the zone choice does more to determine the outcome than almost any design decision.
Zone selection is a judgement, and it is the point where assessments most often get challenged. A site on the edge of a town, backing onto open countryside, can be argued into two adjacent zones with entirely different limits. The safe approach is to state the zone, give the reasoning, and check it against any zone the council's own lighting or dark skies policy specifies. Some local plans and National Landscape management plans set zones explicitly.
Where the council has a designated dark sky area nearby, assume the tighter zone unless you can show otherwise. We have set out the reasoning process in more detail in a note on selecting the right ILP environmental zone.
The curfew time also comes from the council rather than the guidance. Many authorities use 23:00, but it is set by condition and it should match the hours the premises actually operate.
Membership and competence expectations
Councils look for one of three things on the front cover: membership of the Institution of Lighting Professionals, membership of the Society of Light and Lighting within CIBSE, or a chartered engineer with demonstrable exterior lighting experience.
What matters underneath the letters is whether the author can do four specific things:
- Build a calculation model in lighting design software using manufacturer photometric data rather than catalogue claims
- Choose and justify the environmental zone against the guidance and any local policy
- Identify sensitive receptors, including ecological ones, and place calculation points correctly on window planes
- Write conditions-ready conclusions that an environmental health officer can enforce
Ask for two things before instructing: an example assessment for a similar use, redacted if necessary, and confirmation of professional indemnity cover. An assessment that has to be defended at appeal is worth having behind an insured practice.
Design and assessment are different jobs
A lighting designer produces a scheme that delivers the illuminance the operator needs on the ground: enough light in the car park for safe movement, uniform enough to avoid dark pockets, and compliant with the relevant task lighting standard.
An obtrusive light assessment asks a different question: what does that scheme do to everybody else. The two roles are frequently held by the same person, which is efficient and slightly awkward, because the assessor is then marking their own homework.
That is not a reason to avoid it. It is a reason to insist the report states the design brief, the standard applied for the task lighting, and the trade-offs made to bring spill within limits. Where a scheme has been reduced in output or re-aimed to pass, say so. Officers trust a report that shows its working far more than one that reports compliance with no iteration visible.
The interaction with ecology is the case where separating the roles really does help. Joint guidance from the Institution of Lighting Professionals and the Bat Conservation Trust deals with bats and artificial lighting at night, and where a site has hedgerows, mature trees, a watercourse or an existing roost nearby, the lighting design has to work around commuting routes. That needs an ecologist's input as well as a lighting one, and it may pull a Bat Survey into the application that the applicant had not budgeted for.
Questions to ask before instructing
- Which environmental zone will you apply, and on what basis?
- Which receptors will you assess, and how did you identify them?
- Will you use manufacturer photometric files for the actual specified luminaires?
- Does the fee include a re-run if the scheme changes, and how many iterations?
- Will you provide conditions-ready wording and a compliance statement for discharge?
- Are you also designing the scheme, and if so how is the assessment kept honest?
Question four saves the most money. Lighting schemes change during fit-out, and an assessment tied to superseded luminaires cannot discharge the condition.
Conditions that follow a lighting scheme
Expect a condition requiring a full external lighting scheme to be submitted and approved before the use starts, with the scheme to include luminaire specifications, mounting heights, aiming angles, isolux contours and predicted vertical illuminance at named windows. Expect a second limb setting curfew hours and requiring the lighting to be turned off or dimmed outside operating hours.
Some councils add a post-installation verification requirement: measured light levels at the receptors, taken after dark by a competent person, submitted within a set period after first use. That is the point where an optimistic model becomes expensive, because the remedy is re-aiming, shielding or replacing luminaires that are already installed.
Reviewing a scheme someone else submitted
If you are a neighbour or an occupier objecting to a lighting scheme, the checks are the same ones an officer applies. Is the environmental zone right for the area. Are your windows among the assessed receptors, and at the correct height and orientation. Does the model use the luminaires actually proposed. Are the results given for both pre-curfew and post-curfew conditions.
Our wider guide to reviewing a specialist report you did not commission covers the general method, and much of it applies directly here.
A Lighting Assessment drafted through PlanScope sets out the structure, the guidance basis and the receptor schedule, and marks every calculated value as still to be confirmed until a lighting professional has modelled the scheme. Councils expect a suitably qualified author for this report type and professional review is strongly advised. If you need someone to review and sign off a draft, the professional directory is the route into that.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
Does a lighting assessment need a specific qualification?
No statutory licence exists and the title is not protected. Councils look for membership of the Institution of Lighting Professionals, membership of the Society of Light and Lighting within CIBSE, or a chartered engineer with exterior lighting experience. What matters in practice is whether the author can model the scheme properly and justify the environmental zone applied.
What is an environmental zone in lighting terms?
It is a classification of the area's existing night-time brightness, running from intrinsically dark locations through rural and village settings to suburban and city centre areas. The obtrusive light limits tighten as the zone gets darker, so the zone chosen affects the result more than most design decisions.
Can the lighting designer also write the assessment?
Usually yes, and most small schemes are done that way. The report should then state the design brief, the task lighting standard applied and any changes made to bring spill within limits, so the council can see the iteration. Officers are more persuaded by a report showing its working than by a bare compliance statement.
What will the planning condition require?
Typically a full external lighting scheme approved before the use starts, including luminaire specifications, mounting heights, aiming angles, isolux contours and predicted vertical illuminance at named windows, plus curfew hours. Some councils add post-installation verification by measurement, which is costly to remedy if the model was optimistic.
Does lighting affect protected species?
It can. Joint guidance from the Institution of Lighting Professionals and the Bat Conservation Trust addresses bats and artificial lighting at night. Where a site has hedgerows, mature trees, a watercourse or a known roost nearby, the lighting design must avoid commuting and foraging routes, which needs ecological input alongside the lighting work.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.