Stair lighting does not light the staircase but the treads. Small light points in the riser or in the wall pick out the edge of every tread, so you see where your foot lands. A ceiling lamp above the stairwell does the opposite: it puts the treads in your own shadow.
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Why a lamp above the stairs does not work
Light from above comes down over your shoulders. Your body is in the way, so the tread you are about to step on lies in darkness. At exactly the moment you need the light, you take it away.
Lighting in the staircase itself sits below your field of view and shines from the side or from above onto the tread. No shadow falls on it, because you are not in between.
For workplaces, standard EN 12464-1 names a figure of 100 lux on a staircase, the same requirement as for corridors and circulation areas. In a home that is not an obligation, but it is a usable floor. How to tell lux and lumens apart is in What is the difference between lumens and lux?
How much light a tread needs
Far less than people think. The Trevo gives 150 lumens out of 1.5 watts, and that is enough to pick out a tread. The Steno sits lower still at 90 lumens.
That low figure is deliberate. You see a staircase from below, so you are looking almost straight into the fixture. A bright light point at eye level dazzles you and makes the stairs less safe rather than more. It is about contrast between tread and riser, not about output.
How many light points
Dutch building regulations prescribe a maximum riser of 188 mm and a minimum going of 220 mm for a home. An ordinary floor-to-floor staircase of 2.60 metres therefore has around fourteen treads, and every other one is enough in practice. The number and the positioning are set out in How much stair lighting do you need?
On 230 volts or on a transformer
This is the point where stair lighting becomes simple or complicated.
If a module runs on 12 volts you need a transformer, you have to work out how many modules fit on it, and low voltage wiring runs the whole length of the staircase. If it runs on 230 volts, you simply loop through from point to point, just like a row of sockets.
The Trevo and the Trevo Smart both run directly on 230 volts and need no separate driver. That saves a transformer above the ceiling and the sum that goes with it, which does apply to spots: see How many LED spotlights can you put on one driver?
Base unit and cover, bought separately
The Trevo system has two parts. The base unit is the recessed light that disappears into the riser or the wall, with a cut-out of Ø46.5 mm. The cover is the visible trim and decides where the light goes.
That is more than a matter of taste. The cover with light below sends everything down onto the tread beneath, so you never look into the light source. The square cover with light all round spreads wider but does let you look towards the LED.
The cover slides off without tools. If you do not like the shape, you swap it without drilling again.
How to switch it
Three ways, from simple to comfortable.
- An ordinary switch. A two-way switch top and bottom, as in any old house with stair lighting.
- A motion sensor. The light comes on by itself as you approach the stairs. The Steno has one built in.
- With colour. The Trevo Smart gives 3 watts of RGBW rather than white alone.
The modules are not dimmable, so putting a dimmer on them serves no purpose. What happens if you do is in Why does your LED lamp flicker?
All the parts are at stair lighting.
How many lumens do you need for stair lighting?
Very few. Our modules give 90 to 150 lumens each and that is enough to pick out a tread. Brighter light dazzles you, because from below you look almost straight into the fixture.
Do you need a transformer for stair lighting?
Not with our modules. The Trevo and the Trevo Smart run directly on 230 volts, so you loop through from point to point with no driver and no calculation.
A light point on every tread or every other one?
Every other one is usually enough, because the light from one tread also falls on the next. On a staircase of fourteen treads that comes to seven modules.