Public spaces
Office indirect lighting
In an office, lighting is a tool regulated by a standard. Indirect light alone does not meet the 500 lux requirement – but it is the only kind that removes screen reflections and makes an 8-hour day bearable.
What the standard requires and what indirect light can do
EN 12464-1 sets 500 lux on the work surface for a display workstation, a glare index UGR of at most 19 and colour rendering CRI of at least 80. 100 lx is enough for a corridor, 500 lx for a meeting room. These are not recommendations but occupational safety requirements.
Indirect light economically delivers 200-300 lx. 500 lx indirectly would need three times the power and would be expensive both to buy and in electricity. The solution is to layer: indirect general light as the base, direct task light on top. Together they meet the standard and are more pleasant than direct light alone.
Why indirect light removes screen reflections
A screen reflection appears when a bright point source – a downlight, a fluorescent tube – shows in the screen glass. The UGR figure measures exactly this: the brighter and smaller the source in the field of view, the higher the UGR. With indirect light the source is the whole ceiling – large and even. Its luminance is low even though there is plenty of light, UGR stays below 16, and not a single bright point shows in the screen.
This is why indirect light pays off in an office even though it costs more than a fluorescent tube: it reduces eye strain and headaches, and those are an office’s most expensive costs.
Two layers
| Layer | Source | Intensity | Control |
|---|---|---|---|
| Indirect general light | Strip at the ceiling edge or in suspended profiles above the workstations | 250-300 lx | Daylight control: dims near the windows when it is bright outside |
| Task light | Desk lamp or ceiling spotlight for the workstation | +200-300 lx → 500 lx in total | User’s own switch or presence sensor |
In practice: an 8-person open office 8 × 10 m, height 2.8 m, white acoustic ceiling
Perimeter 36 m, but the window wall is left out (daylight): 28 m of strip at the ceiling edge in total.
17 W/m because of the tall room and the 300 lx target = 476 W. Depending on grouping, three or four 200 W DALI drivers.
An acoustic ceiling reflects about 75 %, and 55 % of the light reaches the floor. 28 m × 1,700 lm × 0.75 × 0.55 / 80 m² ≈ 245 lx general light. Plus desk lamps giving 300 lx at the workstations, for 545 lx in total.
Daylight control dims the window-side strips to 40 % during the day – a 30 % saving in electricity. Materials about €1,800, DALI control €800.
Open-plan office – light lines or the ceiling edge
In a small office the ceiling edge is enough. In an open space wider than 6 m the middle stays dim, and then suspended light lines are added: an aluminium profile hanging 40-60 cm below the ceiling that lights both up to the ceiling (indirect) and down onto the desks (direct). One line for each row of workstations. A two-directional profile does both from the same strip.
Image: a suspended light line in an open office – two-directional profile, light up to the ceiling and down onto the desks. No photo yet – to be added when a project has been photographed.
| General light | 250-300 lx indirectly |
| Workstation | 500 lx in total, UGR ≤ 19 |
| Strip power | 14.4 W/m for a 2.5 m room, 17 W/m for 2.8 m and above |
| Colour temperature | 4000 K – alertness, not tiring. The same throughout the space |
| CRI | ≥ 90 (the standard requires 80, but 90 shows colours correctly) |
| Control | DALI: daylight control, presence, groups by workstation row |
| Acoustic ceiling | Reflectance 70-80 % – check the manufacturer’s figure, it affects sizing |
Daylight control pays for itself
In an office the lights burn 2,500 hours a year. A DALI sensor on the window wall dims the strips when it is bright outside – a saving of 25-35 % in electricity. €800 of control pays for itself in 3-4 years, and it is the same system that handles scenes and presence.
Meeting room – face light for video meetings → · For architects – standards → · Dimming and control →
Office project → LedStore
Frequently asked questions
How is indirect lighting done in an office?
At the ceiling edge in a small office, with suspended light lines in an open space wider than 6 m. Indirect light is general light of 250-300 lx, and direct task light is added at the workstations to reach 500 lux.
Is indirect light enough for an office?
Not on its own. EN 12464-1 requires 500 lx at the workstation, and indirect light economically delivers 250-300 lx. Layered with direct task light it meets the standard and is more pleasant than direct light alone.
Does indirect light remove screen reflections?
Yes. Reflections come from bright point sources. With indirect light the source is the whole ceiling, whose luminance is low even though there is plenty of light – UGR under 16, not a single bright point in the screen.
Which colour temperature for an office?
4000 K. Neutral light supports alertness during the working day. 3000 K feels sleepy in an office and 5000 K clinical. The same tone throughout the space.
How much does indirect lighting cost for an office?
€40-80 per square metre including strip, profile, driver and control. An 80 m² open office is about €2,600 in materials. Dropped ceiling and electrical work come on top.
What does UGR mean?
Unified Glare Rating – a glare index. The brighter and smaller the light source in the field of view, the higher the figure. In an office the limit is 19. Indirect light from a large ceiling stays below 16.
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