Workplace Illuminance: Meeting EN 12464-1 and Germany's ASR A3.4 with Lighting Control

Lighting control may save energy, but never at the expense of the required illuminance. The key reference is EN 12464-1 (lighting of indoor work places), a European standard. In Germany, ASR A3.4 (the Technical Rule for Workplaces on "lighting and visual contact") applies as well. Properly planned, the two fit together: constant light and daylight control hold exactly the required value instead of exceeding it, and occupancy control only reduces the light where nobody is working at that moment. This guide is for operators, occupational safety specialists and planners who have to ensure both.

EN 12464-1 and ASR A3.4: what each one covers

The two sets of rules complement each other:

In Germany, an employer who complies with the ASR can assume that the requirements of the Workplace Ordinance are met. EN 12464-1 is the lighting designer's tool and goes further on some points, such as uniformity, glare limitation or context-related adjustments to the values. In practice, an installation is designed to EN 12464-1 and, in Germany, checked against ASR A3.4.

The basic principle: maintained illuminance

Both sets of rules work with maintained illuminance. This is the value that must not be undercut at any time in the area of the visual task, even when the luminaires age or get dirty or the room surfaces darken.

So that the maintained value is still reached at the end of the maintenance cycle, the lighting designer plans with a maintenance factor. As a result, a new installation delivers considerably more light than required when it is new. Without control, you pay for this reserve for years even though nobody needs it.

For office workstations with writing, reading and screen work, a maintained value of 500 lx usually applies. For warehouses, production, traffic routes, sanitary rooms or special areas, the tables give their own values, which depend on the activity. Always take these values from the current version of the rules, not from rules of thumb.

Constant light and daylight: holding the setpoint instead of exceeding it

Controlled lighting saves energy without touching the maintained value. Two functions work together here:

• Constant light control: the sensor measures the brightness and dims the luminaires just far enough to reach the setpoint exactly. When the installation is new, the design reserve is dimmed away, and as it ages, the system adjusts automatically.
• Daylight control: when daylight comes in, the artificial light only adds the amount that is missing. In zones near windows or under rooflights, the artificial light is often dimmed a long way or switched off, while interior zones stay fully lit.

This requires dimmable luminaires. Our guide to dimmable LED luminaires with DALI and 1–10 V explains which interface is the better choice. You can read how daylight control works in detail under daylight harvesting.

Important: setpoint and measuring point

The sensor does not measure on the work surface, but at the ceiling or in the luminaire. It "sees" reflected light. The relationship between the sensor value and the actual illuminance on the desk depends on the room geometry, surfaces and furniture. That is why the setpoint at the sensor is never simply "500", but has to be matched to the measurement at the workstation during commissioning.

Occupancy control: dimming only where nobody is present

Occupancy sensors reduce the light when a zone is not occupied. This is compatible with ASR A3.4, because the maintained value applies at the visual task, and where nobody is working there is no visual task. What matters is planning that guarantees this:

• Detection: every workstation has to be detected reliably, even during quiet screen work. Presence detectors are more sensitive for this than simple motion detectors, see presence vs motion detectors.
• Zoning: divide zones so that occupied areas stay fully lit while empty neighbouring zones dim down.
• Hold time: choose it so that short pauses in movement do not lead to dimming.
• Background light instead of darkness: on traffic routes and in adjoining areas, a reduced background light can make more sense than switching off. The guide to background light and the corridor function describes how this works.

Safety lighting is a separate system with its own requirements and is not affected by occupancy control.

Choosing sensors by room height

Detection depends heavily on mounting height. For offices and rooms with normal ceiling heights, sensors such as the IFS105SE are suitable, for mounting heights up to approx. 5.5 m. In halls and warehouses, high bay sensors such as the EFS106 work at mounting heights of 6 to 12 m. For rooms where people sit quietly for long periods, the EFS107E combines PIR, ultrasound and a daylight sensor. The sensor finder helps you choose, and the grid planner helps you plan positions.

Calibration and verification

A lighting control system is only as good as its commissioning. These steps are important for keeping to the required illuminance:

• Measure in darkness: set the constant light setpoint with a lux meter at the workstation, without any influence from daylight.
• Measure in daylight: check whether daylight control also holds the maintained value in the interior parts of the zone.
• Test the occupancy function: check detection areas and hold times at the actual workstations.
• Document: record setpoints, measurement results and settings. They are also useful for the risk assessment.
• Readjust after alterations: new furniture, partitions or changes of use alter the reflection and therefore the control.

With monitoring via the AU-Manager, which is always part of our projects, you can see dimming values, occupancy and consumption per zone during operation. Anomalies, such as a zone that permanently runs at full load, are noticed early as a result.

Combining legal requirements and comfort

Alongside occupational safety rules, Germany's Building Modernisation Act (GModG) requires automatic lighting control by 31 December 2029 in non-residential buildings with systems above 70 kW; zoning and occupancy detection are "should" requirements and therefore the normal case. A control system that complies with ASR A3.4 and also responds to demand serves both sets of requirements. For an overview, see lighting control under the GModG. You can calculate how much energy the control saves in your building with the savings calculator. For office spaces, you will find further advice under office lighting control and hybrid working and on the page on offices and workplaces.

How we can help

Our focus is retrofitting: we turn existing LED luminaires with dimmable 0-10 V or DALI drivers into intelligent lighting using sensors and app-based lighting management, with no new luminaires and no new control cabling. Details are on our retrofit page.

We survey your rooms on site, plan sensors and zones to suit the visual tasks, and show you the lighting control in advance in 3D in Sensora. We usually handle the installation ourselves, or your own electrical contractor can do it if you prefer. During commissioning we match the setpoints, and monitoring lets you keep an eye on operation. Get in touch if you would like to control your lighting in a compliant and economical way.