In a warehouse, lighting checks are almost always done at floor level: lux meter at 0.85 m, a few points read in the aisles, average calculated, level compliant. The report is good. Six months later, forklift drivers work with a torch hooked to the truck and picking errors do not fall. The problem is not in the measurement. It is in the plane on which it is taken.
The working plane of a warehouse is not horizontal
In an office, the visual task lies flat. Horizontal illuminance correctly describes what the operator sees. In a racked building, the visual task is vertical: a location label, a barcode, a batch number, a parcel at the back of a bay. What the eye has to make out is on the rack face, at heights ranging from the floor to the last level served. Almost never on the floor.
NF EN 12464-1 does not ignore this. It distinguishes unmanned storage aisles from aisles where people move about, with a much higher requirement in the second case · the order of magnitude used is about 150 lux for an aisle walked through, against a much lower value for an aisle crossed only by automated vehicles. Above all, its revision gave more room to vertical illuminance (Ev) and cylindrical illuminance (Ez), which describe the light received by a standing plane or by a face, not by the concrete.
Two warehouses can show the same average illuminance on the floor and a considerable difference on the rack face. It all depends on the aisle width, the storage height, the beam angle of the optics and the alignment of the luminaires with the aisles. The first building is legible at head height as well as at the third level. The second forces you to come closer, to come down, to light some other way.
A warehouse compliant at floor level can remain illegible at four metres. Compliance and usability are simply not measured on the same plane.
The rack absorbs what the floor receives
A storage aisle is a canyon. Two tall, dark walls, cluttered with pallets and stretch film that reflect almost nothing. Where an office floor benefits from reflections on the walls and ceiling to even out levels, an aisle of racks has no useful reflection: light that does not reach the rack face directly will never reach it. The higher the storage and the narrower the aisle, the worse the ratio between floor illuminance and vertical illuminance becomes.
This is also why point-by-point relamping so often disappoints. Repeating one for one a layout designed for an empty building reproduces the same defect with lower consumption.
Quantity | Where it is measured | What it determines | Common pitfall |
|---|---|---|---|
Horizontal illuminance (Eh) | Circulation plane, 0.85 m or at floor level | Safety of movement, basic compliance | Enough to pass a check, not to make the rack legible |
Vertical illuminance (Ev) | Rack face, at several level heights | Reading labels, quality control, picking | Rarely requested, so rarely calculated |
Uniformity (U0) | Along the whole length of the aisle | Visual comfort, adaptation of the eye while moving | Good average, alternating light and dark areas |
Glare (UGR) | In the forklift driver’s line of sight, often upwards | Fatigue, precision of manoeuvres at height | Bare optics visible from the driving position |
Narrow optics: geometry before power
The usual reflex is to increase the luminous flux. It is the worst lever. With a wide beam, a large share of the light falls on top of the pallets, on the upper beams and on areas already lit, without ever going down into the aisle. You pay for energy to light a rack deck.
In a high, narrow aisle, a narrow beam does exactly the opposite: it pushes the flux down to the floor and lights both faces over their full height. High bays with interchangeable optics make it possible to adjust the beam angle zone by zone without changing range: a tight beam in high aisles, a wide beam in picking or dock areas. Asymmetric optics, for their part, deliberately send the flux towards the faces rather than towards the middle of the aisle.
In very narrow aisles, particularly with turret trucks, a continuous line gives better results than a point source. Linear battens mounted in a continuous line above the aisle axis remove the light-dark alternation that the eye has to compensate for with every movement, and keep a stable vertical illuminance along the whole length. All the configurations specific to these buildings are grouped in the luminaires for storage and logistics ranges.
Laying out according to the storage plan, not the building grid
Most warehouse installations follow the roof frame grid: one row of luminaires per bay, evenly spaced. It is simple to install and consistent as long as the building is empty. As soon as the racking is up, the logic changes. A luminaire above a rack upright no longer lights anything useful; a luminaire offset by 80 cm from the aisle axis lights one face correctly and leaves the other in shadow.
The rule is simple to state and more demanding to keep: the layout follows the storage plan, one row per aisle, centred on the axis. This means having the real racking plan, the beam heights, the aisle widths and the areas likely to be reconfigured. This is precisely what a photometric study carried out on the storage plan rather than on the site plan produces: a 3D model of the racks, calculations on vertical faces, and a layout that remains right after installation.
Storage moves. Aisles shift, heights change, a picking area becomes a bulk storage area. Electrical zoning by aisle, with fixing points or cable trays provided for an offset, avoids having to take everything down three years later. This point is decided upstream, during the lighting audit, not at installation.
Presence detection is planned aisle by aisle
In a warehouse, occupancy is intermittent and very localised. One aisle in ten is in use at any given moment. It is the largest source of savings after replacing the sources, and most often poorly used: management by large zone, or even by building, permanently lights empty aisles.
The relevant division is the aisle. Each aisle is an independent detection zone, with several detectors, because a sensor placed at 10 metres in a canyon of racks covers a limited length. A few principles hold in almost every case:
- A standby level rather than switching off completely: vehicle traffic, video surveillance and the perception of adjacent aisles do not cope well with total darkness.
- A time delay set on the real picking rate, to avoid constant cycling, which is tiresome for the operator as well as for the equipment.
- Gradual dimming, never an abrupt switch: the eye takes several seconds to adapt, and the driver keeps moving during that time.
- An emergency lighting circuit separate from the detection, in accordance with NF EN 1838.
Compatible sensors, power supplies and control modules are grouped in the lighting safety and control ranges. The settings, for their part, are adjusted on site after a few weeks of operation.
The maintenance factor, the forgotten variable of dusty environments
A lighting study calculates levels when new, then applies a maintenance factor that anticipates drift: LED lumen depreciation, failures, dirt on the optics, soiling of the walls. In a clean tertiary building, this factor is most often around 0.80. In a warehouse with combustion-engine trucks and dust from cardboard, wooden pallets or agricultural produce, it frequently drops to between 0.60 and 0.70, depending on the site and the cleaning frequency chosen.
The gap is not cosmetic. An installation calculated at 0.80 on a site that behaves at 0.65 will, after a few years, deliver nearly 20 % less light than the announced level · on the rack face, that is, where the margin was already smallest. Three precautions limit the risk: use a factor consistent with the real environment and write it into the study, choose smooth, sealed diffusers that are easy to wipe, and put the cleaning frequency in the maintenance plan rather than leaving it to general judgement.
What this changes for the budget
A regulatory point to know before building a financing plan: the order of 23 February 2026, in force since 25 February 2026, abolished the CEE sheets BAR-EQ-110, BAT-EQ-127 and IND-BA-116. There is no longer a standardised bonus for indoor lighting renovation. Offers that still announce one for a warehouse should be set aside. Outdoor lighting renovation remains eligible through sheet RES-EC-104, revised by the order of 24 November 2025: manoeuvring yards, lorry parks and site roads fall within this scope.
The real levers lie elsewhere: long-term leasing over 3 to 5 years, calibrated so that the monthly saving covers the instalment, a payback time calculated zone by zone rather than as a building average, and related items still eligible such as building management systems, destratification or variable speed drives. An example of the method, taken outside warehousing but representative: in an airport arrivals hall, 398 luminaires were brought down to 315, with consumption going from €12,197 to €3,340 a year, a saving of €9,027 a year. Budget of €27,405, payback time of 37 months, €16,880 net over five years. The reduction in the number of light points comes from the calculation, not from a commercial trade-off.
The same logic applies in a warehouse, with one major nuance: the variable to hold is neither the number of luminaires nor the watts per square metre, but the illuminance achieved on the rack face. This is what the projects already completed on industrial and logistics sites show.
Where to start
Three elements are enough to know whether a warehouse is really usable: the up-to-date storage plan, a few vertical illuminance measurements on the rack face at different heights, and the record of real consumption. The rest is calculated. At Luminance Consulting, the audit and the photometric study are free, site visit and 3D modelling included · we are paid on the solution we supply and have installed, not on the engineering. Get in touch to have what really matters in your aisles measured.
