The short answer
An LED upgrade does not automatically improve compliance. Lighting compliance is not just about how many lux reach the desk; BS EN 12464-1:2021 also sets limits for uniformity, discomfort glare (UGR), colour rendering and, since the 2021 edition, gives more attention to flicker, stroboscopic effects and the illuminance on walls and ceilings. A retrofit that improves one of these can easily worsen another.
The legal duty is unchanged: regulation 8 of the Workplace (Health, Safety and Welfare) Regulations 1992 requires suitable and sufficient lighting, and for screen users the Health and Safety (Display Screen Equipment) Regulations 1992 require glare and reflections on screens to be prevented. A new installation that creates glare can therefore introduce a problem where there was none.
Glare and UGR after an LED upgrade
What UGR measures
The Unified Glare Rating is a calculated index of discomfort glare from luminaires as seen from a typical viewing position. It depends on the luminance of each fitting, its size and position in the field of view, and the background luminance of the room. Values run on a scale of 10, 13, 16, 19, 22, 25 and 28; lower is better. BS EN 12464-1:2021 sets a maximum per task, for example:
| Area or task | Maintained illuminance | UGR limit |
|---|---|---|
| Office writing, reading, data processing | 500 lx | 19 |
| Technical drawing | 750 lx | 16 |
| Warehouse manned rack gangways | 150 lx | 22 |
| Corridors and circulation | 100 lx | 28 |
Why LEDs often fail on glare
LED chips concentrate a lot of light in a small area, so their luminance can be very high. A fluorescent tube behind a louvre spreads its output over a long, relatively dim surface; an LED panel or batten with a thin diffuser may look much brighter at the same lux level. Common retrofit glare problems include:
- bare or lightly diffused LED battens replacing louvred fluorescent fittings in offices;
- “low-cost” edge-lit panels without a published UGR value, or with a UGR only achieved in a specific room geometry;
- high-bay LEDs with narrow optics mounted lower than intended, so the source sits in the line of sight;
- over-lit spaces where the fittings are running at full output with no dimming.
Because UGR is calculated, a lux meter reading alone cannot confirm it. A proper survey records the luminaire model, photometric data, mounting height and room dimensions so glare can be assessed against the limit, alongside observation of reflections on screens.
Other ways a retrofit can reduce compliance
Uniformity
Fewer, more powerful fittings can produce bright pools and dark bands. An office average of 600 lx means little if desks between luminaires measure 300 lx; the standard asks for uniformity of 0.60 on office task areas.
Dark walls and ceilings
Fluorescent fittings often threw light upwards and sideways. Recessed LED panels and downlights tend to light only the floor and desks, leaving the room feeling enclosed and increasing the contrast between bright luminaires and dark surroundings, which also worsens glare.
Flicker and stroboscopic effects
Poor-quality LED drivers can cause visible flicker or stroboscopic effects, where rotating machinery appears slowed or stationary. That is a real hazard in workshops and factories, and flicker is a common trigger for headaches and complaints.
Colour rendering
BS EN 12464-1:2021 typically asks for Ra 80 in offices and higher values where colour judgement matters. Some budget LED products only just meet Ra 80, or fall short, and colour temperature can vary between batches.
Emergency lighting
Conversions that alter emergency luminaires must still meet BS EN 1838:2024 escape route levels (1 lx on the centre line of escape routes, 0.5 lx in open areas) and be tested in line with BS 5266-1:2025.
How to protect LED retrofit compliance
- Measure first. A baseline lux survey records what the existing system delivers. See our guide to LED upgrades and lux levels.
- Specify performance, not wattage. Write the target illuminance, uniformity, UGR, colour rendering and flicker performance into the contract.
- Ask for a lighting design. A calculation for the actual room, not a generic data-sheet UGR, shows whether limits will be met.
- Commission and dim. Set output to the design level rather than leaving fittings at 100%.
- Verify on site. A post-installation survey checks illuminance and uniformity on a measured grid and records the details needed to assess glare.
- Listen to occupants. Complaints of headaches, squinting or screen reflections after a retrofit are a strong signal. Our article on why employees complain about lighting covers the patterns.
Typical fixes
Most retrofit compliance problems can be fixed without starting again: replacement diffusers or prismatic lenses, louvre or microprismatic optics, dimming via the existing drivers, re-positioning a few luminaires, or adding wall-washing or uplighting to raise background luminance. Flicker problems usually need replacement drivers or fittings.
Check your LED installation
If you have recently upgraded to LED, or are about to, an independent survey is the quickest way to know whether the new lighting is genuinely compliant. Polarity Lux surveys offices, schools, warehouses and industrial premises across London and the South East. A single-floor office or retail survey starts from £175. Book an LED compliance check or see our fixed prices.
Frequently asked questions
Can LED lighting cause glare even at the correct lux level?
Yes. Glare depends on the brightness of the luminaire as seen by the occupant, not just the lux on the desk, so a correctly lit room can still exceed its UGR limit.
What UGR is required for an office?
BS EN 12464-1:2021 sets a UGR limit of 19 for office writing, reading and data-processing tasks, and 16 for technical drawing.
Can a lux meter measure UGR?
No. UGR is calculated from luminaire photometry, positions and room geometry. A survey records those details alongside lux readings so glare can be assessed.
How do I fix glare after an LED retrofit?
Common fixes include better diffusers or optics, dimming fittings to the design level, re-positioning luminaires and raising wall and ceiling brightness to reduce contrast.