The scheme for reducing consumption in the tertiary sector requires the buildings concerned to lower their final energy consumption and to declare it every year. In the field, the question is never "what needs to be done?" but "where do we start?". In most of the office buildings we audit, the answer is lighting: the quickest item to rework, the simplest to measure, and the one that disrupts activity the least.
Why lighting almost always comes first
Three reasons.
- It can be measured. An installed power, operating hours, a meter reading: the saving is calculated before the works and checked afterwards. Few items offer this clarity.
- It can be reworked quickly. A floor is treated zone by zone, in the evening or storey by storey. No structural work, no shutdown of operations, no reworking of the heating and cooling networks.
- It has a side effect. A luminaire consumes and dissipates. Lowering the installed power also reduces internal heat gains in summer, and therefore the air conditioning load. The extent depends on the building, but the direction is always the same.
The building envelope, ventilation or hot water production involve budgets and lead times of another kind. Lighting scores points early, while the other projects are being prepared.
What the logic of the scheme really implies
The principle is simple to state: reach a consumption target, either through a reduction relative to a documented reference year, or in absolute value according to the category of activity, with successive milestones and an annual declaration of consumption on ADEME’s collection platform.
The practical consequence is less discussed: the data matters as much as the technical work. A successful renovation that is not tracked does not appear in the declaration. Conversely, a poorly reconstructed reference year can put a target out of reach even though the building has improved. Before buying luminaires, you need to know what you consume and on what basis you will be compared.
What you declare is not an installed power, it is energy consumed. Two floors fitted with the same equipment can show large differences depending on real hours and controls.
Isolating lighting consumption from the rest of the electricity item
In most office buildings, lighting is not metered separately. It is diluted in a "sockets and lighting" circuit or in the floor’s main supply. Without separation, you do not know where the savings potential lies and you will not be able to show what the renovation has delivered.
Method | What it provides | Limit |
|---|---|---|
Sub-metering on a dedicated circuit at the main switchboard | Real consumption, continuously | Requires a separate lighting circuit, otherwise rewiring works |
Inventory of luminaires cross-referenced with operating hours | A reliable order of magnitude, zone by zone | Depends on the quality of the survey of real hours |
Spot measurement (clamp meter, logger) | A snapshot over a few weeks | Captures neither seasonality nor exceptional uses |
Feedback from DALI-2 or D4i drivers to the BMS | Monitoring by zone, after the works | Requires controllable luminaires and a properly configured BMS |
None is sufficient on its own. A lighting audit carried out on site combines them: metering where it exists, inventory by zone, and survey of real uses. Surprises almost always come from there: floors lit during cleaning, circulation areas lit continuously, car parks and halls forgotten in the time schedules.
Levels by task: NF EN 12464-1 as the starting point
Reducing does not mean lowering the levels. NF EN 12464-1 sets the illuminances to be maintained on the work area, together with glare limits and uniformity requirements. The French Labour Code, for its part, imposes minimums and leaves the employer responsible for visual working conditions.
Area or task | Maintained illuminance | Glare (UGR) |
|---|---|---|
Writing, typing, reading, data processing | 500 lx | ≤ 19 |
Technical drawing, CAD | 750 lx | ≤ 16 |
Meeting and conference rooms | 500 lx (to be adjusted) | ≤ 19 |
Reception desk | 300 lx | ≤ 22 |
Archives | 200 lx | ≤ 25 |
Circulation areas, corridors | 100 lx | ≤ 28 |
These values are read together with their complements: uniformity of at least 0.60 on the work area, colour rendering of at least 80, and a minimum of light on the walls to avoid the cave effect, around 50 lx on the walls and 30 lx on the ceiling in permanently occupied rooms. NF EN 1838 deals separately with emergency lighting, which is required whatever the renovation.
The most frequent source of savings is the opposite of what one imagines: over-lighting. Floors fitted fifteen years ago often measure well above the target, because the layout plan was copied from one storey to the next without taking partitions or facades into account. You then do not replace one luminaire with another: you remove some, reposition the others over the real workstations, and choose luminaires designed for workspaces whose photometry matches the ceiling grid.
Screens: glare is the first reason for rejection
A tertiary renovation rarely fails on consumption: it fails on comfort. Beyond UGR, the standard limits the average luminance of luminaires seen at the angles likely to be reflected in a screen, around 3,000 cd/m² in common situations and 1,500 cd/m² for highly reflective screens or demanding tasks. NF X35-103 completes the subject on the visual ergonomics side: position of the screen relative to the windows, contrasts, management of blinds.
Four mistakes come up often.
- Fitting LED tubes in old louvred luminaires. The photometry of the luminaire is no longer the one the manufacturer designed, and the stated UGR no longer means anything.
- Choosing a panel on its efficacy in lumens per watt alone, without looking at its luminance at wide angles.
- Laying out the rows perpendicular to the facades and lines of sight, instead of offsetting them from the workstations.
- Treating meeting rooms like offices, when they need dimming and several scenes.
The choice of LED panels for modular ceilings is therefore made on the photometric curve and the UGR value in the real configuration of the room, not on a generic data sheet.
Presence detection and dimming: the savings that remain after the equipment
Replacing the installed base gives a first step. The second comes from the time during which you stop lighting for nothing. The two add up, if they are thought through together.
- Presence detection in circulation areas, toilets, meeting rooms, archives, plant rooms and car parks: the zones where the gap between lighting time and occupancy time is widest.
- Daylight-linked dimming for the rows near the facades, which can go down very low, or even switch off, for a good part of the year.
- Fine zoning rather than a single control per storey: daylight does not reach two metres and eight metres from the window in the same way.
- Time delays set with the occupants, and a local manual control kept. A poorly timed detector ends up neutralised with adhesive tape.
- Explicit scenes for the end of the day, cleaning and weekends.
Depending on the site, the share of lighting time without real occupancy is rarely marginal, and it is most often concentrated in circulation areas and meeting rooms. It is also the cheapest item to correct, since it requires neither drilling nor ceiling rework when control and detection devices are built in from the design stage. The protocol must be decided when the equipment is chosen: a DALI-2 or D4i installation can be controlled and metered, an on/off installation can only be caught up at the cost of a second project.
Open-plan offices: treating light and acoustics in one go
A ceiling is opened only once. In open-plan floors, noise nuisance often comes before visual discomfort in internal surveys. Acoustic luminaires combining lighting and absorption deal with both subjects in the same operation, without a second disruption six months later. The question arises at the study stage, because it changes the grid and the suspension height.
Financing: what changed on 25 February 2026
This deserves to be said clearly: proposals are still circulating with bonus lines that no longer exist. 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 CEE bonus for indoor lighting renovation. Any offer that announces one should be checked line by line.
What can still be used: outdoor lighting, eligible through sheet RES-EC-104 revised by the order of 24 November 2025, which covers car parks, private roads and surroundings; and related items still supported, notably building management systems, destratification and variable speed drives. For indoor lighting, the financing now relies on two levers: a payback time calculated zone by zone, and long-term leasing over three to five years in which the monthly saving covers the instalment.
Airport arrivals hall · completed operation | Before | After |
|---|---|---|
Number of luminaires | 398 | 315 |
Annual consumption | €12,197 | €3,340 |
Annual saving | €9,027 | |
Project budget | €27,405 | |
Payback time | 37 months | |
Net result at 5 years | €16,880 |
This is not an office floor, and the hours of an airport hall are not those of a tertiary building. What carries over is the method: fewer light points, better placed, a calculation zone by zone, a payback time known before signing rather than hoped for afterwards.
How we work
Luminance Consulting works in five steps: identify the savings potential, propose the solutions, build the financing plan, have the installation done, by our team or by the installer of your choice, then follow the project through to commissioning and the check of levels on site. This last point is not decorative: a level checked after the works makes it possible to defend both the comfort of the occupants and the declared reduction.
The audit and the photometric study are free, site visit and 3D modelling included. It is a deliberate choice: we are paid on the solution we supply and have installed, not on the engineering. The design office is one skill among others, alongside the audit, the choice of luminaires and the field experience built up since 2013 on tertiary and industrial sites · Airbus Defence and Space, Sanofi, Michelin, La Banque Postale, Crédit Agricole, Tarbes-Lourdes-Pyrénées airport, among others. The equipment comes from our own brand of professional LED luminaires, Rexylum, and from partners such as Filamento Lighting and Tridonic.
We work throughout France, with a site visit for the survey. To put a figure on the lighting savings potential of your offices before your next declaration, get in touch with our teams: site visit, 3D modelling and payback calculation zone by zone are free.
