The appointment is set for six in the morning, before the first shift starts. It is the only slot when the workshop is lit, empty of production, and when the rising sun will not yet distort the readings. A lighting audit turns on this kind of detail.
What a lighting audit sets out to establish
An audit pursues three distinct objectives. Establish the real condition of the installation, zone by zone, on measured values. Place that condition against the requirements that apply to the premises. Put a figure on the gap, in works as well as in consumption.
This work cannot be done from a table of installed wattages. Two workshops fitted with the same luminaires, at the same height, give different results depending on dirt build-up, the colour of the walls and the layout of the machines.
Preparing the visit: plans, bills, operating hours
A prepared visit runs in one go; an improvised visit almost always requires a second trip. Four items are worth gathering beforehand: the building plans, the electricity bills for the last twelve months, the operating hours by zone and the history of maintenance work.
Operating hours are the most underestimated piece of data. The gap between the posted opening hours and the real hours the lights are on, extended by cleaning, night shifts and zones that are never switched off, completely changes the consumption calculation.
Illuminance readings, zone by zone
Measurement is done with a lux meter, with a cosine-corrected cell and up-to-date calibration. The instrument must suit the purpose: an entry-level lux meter is enough to get a rough picture, while a survey meant to appear in an enforceable report requires an instrument of known class and a recent calibration certificate.
The measuring points follow a grid whose spacing depends on the dimensions of the room, with meshes close to square and a perimeter band left out along the walls. The number of points increases with the area: measuring four points in the middle of a workshop of several hundred square metres says nothing about the real uniformity, which is precisely the value the audit must establish.
The measuring height follows the use: the working plane in offices, generally taken at 0.80 metre, the floor for circulation areas, the real height of the work surface at the workstation. A reading taken at hand height on an assembly station at bench height compares to nothing.
Two precautions determine whether the figures are valid. Daylight must be neutralised, by measuring at night or by taking a double reading, installation on then off, to subtract the outside contribution. Luminaires must be stabilised before the reading, a few minutes for an LED source, longer for discharge sources still in service.
Beyond horizontal illuminance
Some zones require other quantities. Vertical illuminance is measured in front of the racks of a warehouse, on the faces of parcels and on faces in reception areas. Emergency lighting is checked along the centre line of escape routes, where the EN 1838 standard requires at least 1 lux, and in open areas, where it requires at least 0.5 lux.
Inventory of the installed base: technologies, heights, condition, access
Alongside the measurements, each zone gets a survey of its installed base: technology, system wattage, number of fittings, mounting height, condition of optics and diffusers, dirt build-up, type of control.
Accessibility is recorded in the same way. A luminaire above a production line, reachable only during the annual shutdown, is not handled like a luminaire reachable by aerial platform on a Saturday morning. This constraint often weighs more heavily on the budget than the unit price of the equipment, as our article on renovating industrial lighting and its order of priority explains.
Spotting compliance gaps and risk areas
Gaps are read against two frames of reference. The French Labour Code sets enforceable minimums by type of space. The EN 12464-1 standard gives the comfort levels expected for each visual task, well above those minimums.
Three situations come up regularly in workshops: a visual inspection station lit at the level of a mere circulation area, a storage zone turned into a picking zone without the lighting following the change of use, and handling aisles where drops in illuminance create shadow areas where vehicles cross.
These gaps rarely come from a design error. They appear because the use of the premises changes faster than the installation: a line moved, an island added, a rack fitted under a row of luminaires. The audit serves precisely to bring the lighting back in line with today’s activity, not the one that existed at commissioning.
What the audit report must contain to be usable
- A zoning plan with the measuring points marked.
- The table of readings, with the required value next to the measured value.
- The full inventory of the installed base and its condition.
- The calculation assumptions: operating hours, energy price used, maintenance interval.
- Costed recommendations by zone, with the associated energy and maintenance savings.
- A ranking of priorities, because no site treats all its zones in the same year.
A report without stated assumptions cannot be defended in front of a finance department. A report without priorities does not turn into a decision.
Priorities are built on three criteria that intersect. The first is the compliance gap, which engages the employer’s liability and therefore comes first. The second is the number of operating hours of the zone, which drives the energy saving. The third is the access constraint, which sets the possible window for the works and sometimes the dominant cost of the package.
From audit to costing: the logical next step
The audit gives the condition and the gap. The photometric simulation gives the layout that closes that gap, with the levels checked before the works. The costing comes next, based on a validated layout rather than an estimate by ratio.
At Luminance Consulting, the visit, the measurements, the DIALux evo simulation and the costed report are carried out free of charge as part of a project. The details of the service are on our lighting audit page, and the LED luminaires for production areas form the basis of the recommendations made in workshops.
To schedule a visit to your site, book an appointment from the contact page.
