Lighting an office to AS/NZS 1680

Step 1

What the standard asks for

AS/NZS 1680 sets how much light a task needs, measured as maintained illuminance on the work plane. For a desk that is a horizontal plane 720 mm above the floor, so that is where every plan on this page is measured, not the floor.

The target depends on what the room is used for. We use 320 lx for an office and for a meeting room, and 160 lx for a reception. Switch the room type to see the same fitting laid out for each.

The layout is suggested by the same engine as the light estimator: the smallest even grid that reaches the target with acceptable evenness.

Step 2

Maintenance factor: why you design brighter on day one

The target is a maintained value: what the room must still deliver after dust builds up on the fitting and the LEDs age. So a new installation has to be brighter than the target to stay above it.

We use a maintenance factor of 0.8, which means the room is designed to give about 25% more light on day one than the target. Drag the slider, or press Replay, to watch the plan fade from new to maintained.

The estimator quotes the maintained figure, so the number you see there is already the one to compare with the target.

Step 3

Uniformity: the average is not enough

An average can hide dark patches. Uniformity (U0) is the lowest lux on the work plane divided by the average, so 1.0 would be perfectly even and a low number means a dark spot somewhere a person will sit.

Here is one room with the same number of fittings. Pull them together and the middle gets bright while the edges go dim. Spread them out and U0 climbs. The plan recalculates as you move the slider, and the two ends are listed under it.

Our estimator aims for a U0 of 0.4 or more, and checks it before suggesting a layout.

Step 4

Spacing and mounting height

Each fitting lights a pool on the desk. How far apart the pools sit compared with how high the fittings are decides whether they merge into an even blanket or leave gaps.

Raise the ceiling and every pool widens and overlaps its neighbours, which evens the light out but also spreads it thinner, so the average falls. Lower it and the pools shrink toward separate spots. Change the number of fittings to move them closer or further apart.

A common rule of thumb is to keep the spacing within about 1.5 times the mounting height (ceiling height less the 720 mm desk). The estimator uses it, and so does this diagram.

Step 5

Beam angle

The beam angle is how wide a fitting spreads its light. A narrower beam, like the 60° option on Geber, puts more of its light straight down onto the desks. A wide beam, like the 90° on Bell, throws more of it out sideways, where some lands on the walls or is lost at the edges of the work area.

To compare fairly, both plans use the same room, the same fitting positions and the same lumens, so only the beam differs. Neither is better in every room: a wide beam covers more of the room from each fitting, while a narrow beam puts more of the same light on the desks.

Step 6

Glare

People in offices look at screens, so offices aim for low glare, rated as the Unified Glare Rating (UGR). A lower UGR is more comfortable.

One of the main things that helps is hiding the bare LED. A deep-recessed downlight keeps the light source up inside the fitting, so from across the room you see the recess wall rather than the LED. Move the slider to see how depth changes what a person looking from the side can see.

These Tunable fittings list a UGR rating in their specifications, lowest first:

• BoltDALI-2 Adjustable DownlightUGR <16
• ChelonDALI-2 Retractable DownlightUGR <18
• BellDALI-2 DownlightUGR <19
• GeberDALI-2 DownlightUGR <19
• EsunaDALI-2 Trimless DownlightUGR <19
• CertumDALI-2 Recessed DownlightUGR <19
• CrickDALI-2 DownlightUGR <19
• ArcaDALI-2 Box DownlightUGR <19
• DiuLED Linear LightUGR <19

UGR values are as published on each product page. Check the rating of the exact variant you specify.

Step 7

Controls: dimming back to target

Because a design always lands a little above the target, controls bring it back. In an office, each room is its own DALI group. At commissioning, an installer sets the group's output so the room measures just at the target, rather than leaving every fitting at full power. Press Commission to watch that happen, and try the other room types.

The watts shown assume the load follows the dim level. That is an approximation, but it shows the direction: lights that are not needed are lights you do not pay to run.

A DALI-2 system can also add:

• Presence sensors that switch or dim a room when nobody is in it.
• Daylight sensors that lower the light near windows when the sun is doing the work.
• Scene keypads and dimmers so people can set the room for a meeting or a presentation.
• Apps, gateways and a BMS interface to adjust and monitor the building.

Our team handles on-site commissioning, and after-service site monitoring and support is available under a maintenance contract. How DALI-2 works is explained step by step in DALI-2 explained.

Wired or wireless: DALI-2, DMX, Casambi, Syncromesh, from a single sensor to a full control system with BMS interface and cloud monitoring, backed by maintenance contracts.