For an office of 20 square metres you come to about five panels. The standard asks for 500 lux at the workstation, and with a utilisation of 0.6 and a maintenance factor of 0.8 that means around 20,000 lumens. At 4,200 lumens per panel, that is five.
Know what you need? View all LED panels (33)
The standard first
EN 12464-1 sets out per type of work how much light should fall on the working plane. The values you need for an office building:
- Workstation, writing and screen work: 500 lux
- Meeting room: 500 lux
- Reception: 300 lux
- Archive: 200 lux
- Corridor and circulation area: 100 lux
Those figures apply on the working plane, so at table height, not on the floor. Lux is lumens per square metre, as explained in What is the difference between lumens and lux?
Why you do not simply do lux times area
That is the calculation error almost everyone makes. Not all the light a panel gives reaches the working plane: some goes to the walls, some to the ceiling, and some is swallowed over the years by dust and ageing.
The professional formula allows for that with two factors:
The utilisation factor says how much of the light reaches the working plane. In an ordinary office with light walls that is around 0.6. Lower in a narrow or dark room, higher in a white room with a low ceiling.
The maintenance factor means your installation still has to comply on its last day, not only on its first. For a clean office, 0.8 is usual.
Together those two mean you have to install about twice as many lumens as the bare sum suggests.
The sum, step by step
For 500 lux in 20 square metres:
- 500 lux times 20 square metres is 10,000 lumens on the working plane
- divided by a utilisation of 0.6 gives over 16,600 lumens
- divided by a maintenance factor of 0.8 gives about 20,800 lumens
The Nova gives 4,200 lumens, so five panels bring you to 21,000 lumens. That fits.
For a corridor of the same 20 square metres the standard asks 100 lux, so a fifth. There, a single panel takes you a long way.
Glare counts as heavily as lux
Enough light from the wrong fixture is not good lighting. For office work, alongside the lux requirement there is a limit on glare, expressed as UGR, and for ordinary screen work that sits at 19.
The Nova sits below 16, which is exceptionally low and matters precisely above a desk where people sit for hours. The background is in What does UGR mean on an LED panel?
Spreading them across the ceiling
Putting five panels in one corner helps nobody. Spread them evenly, and keep the distance to the walls at about half the distance between them. Otherwise it gets too dark by the windows while the middle is overlit.
In a grid ceiling that is easy: you have a 600 by 600 grid and simply choose which cells become light. How the laying-in works is in How do you mount an LED panel?
If there are desks, mind the direction too. A long panel across, above a desk, casts less shadow than a square panel hanging directly behind you. The choice between the two sizes is in Which size LED panel: 60x60 or 120x30?
When to let the sum go
With a ceiling higher than three metres, in a room with dark walls, or for work where colour has to be exactly right, the rule of thumb no longer holds. A lighting calculation with the real dimensions and reflectance values is then the only reliable route.
The range is at LED panels, with a dimmable and a non-dimmable version per model.
How many lux should an office have?
EN 12464-1 asks for 500 lux at the workstation for writing and screen work. For a corridor that is 100 lux, for an archive 200 and for a reception 300.
How many LED panels do I need for 20 square metres of office?
About five of 4,200 lumens. You need around 20,000 lumens, because with a utilisation of 0.6 and a maintenance factor of 0.8 you install over twice the bare sum.
Which UGR do I need for an office?
For ordinary screen work the limit is UGR 19. Lower is more comfortable: the Nova sits below 16, which is noticeable where people sit under it for hours.