Three ways to light a Bathroom

Technical editor Alan Tulla considers the challenges of lighting one of the most oft-visited parts of a building...

 

When I meet people for the first time and tell them I’m a lighting consultant, it can take them a little while to get their head round what that means. Once they have, their next question is usually along the lines of: ‘Sounds interesting – can you do anything about bathrooms and toilets?’

There are two aspects of lighting in toilets that people don’t like. First people complain that there is too much light on the top of your head and not enough on your face when looking in the mirror. The cause is usually ’alogen acne – the overuse of recessed low-voltage downlights in the ceiling.

The second problem is that of windows opposite mirrors causing your face to be seen in silhouette. This is harder to deal with because the window layout is often decided well before the lighting design. Raising the window above eyeline is normally impractical and blocking it is a waste of freely available light. Let’s take a look at three ways of dealing with these problems in a typical office toilet.

Design considerations

The room in these three examples is typical of the toilet facilities in an office building or small conference centre. BS EN 12464 recommends 200 lx for this type of area. This illumination level also applies to individual toilets if fully enclosed. It also recommends a colour-rendering index above 80, and that luminaires should be suitable for damp and humid situations. None of this is particularly onerous.

Because buildings tend to be constructed with water supply and drainage built into the core, many of these areas have no natural light. If there is any daylighting, the window is normally opposite the wash basins, hence the problem with silhouetting in mirrors.

LUX VERDICT
It’s amazing how many bathrooms and toilets are still lit with tungsten halogen. Normally, one or more of the lamps has failed and you get bright illumination on top of your head but your face is in shadow. Switching to LED with a wider beam (and that’s important), saves energy, reduces maintenance and gives a better looking result. The caveat being that the LEDs must have good colour rendering and can’t be too cool.
  Unfortunately, there is still a tendency to judge lighting by the horizontal illumination level. In bathrooms, it is the vertical that is important and this is where the third option with light around the mirrors scores so well

This first option uses our old friend the 50W MR16 downlight. Cheap to buy, simple to install, brilliant colour rendering. What’s not to like?

Well, one big objection is that the energy consumption is through the roof. The toilets are likely to be one of the spaces in a building that’s illuminated for the longest, so big financial savings can be made by cutting energy use.

One quick solution is to use a presence detector, but this only really works in smaller premises. In larger ones, the space will be occupied by at least one person for most of the time. If you do fit a presence detector, don’t forget to set the dwell period for a sensible length of time – no one likes to be left sitting in the dark.

The lamp life of these 50W fittings is not great either. Two thousand hours is the life of a standard MR16 although you can get 4,000 by paying more. That certainly means a complete lamp change every year, maybe every six months.

But my biggest objection is the light distribution. There’s plenty of light, but not where you want it. Almost all the ‘tasks’ required here need good vertical illumination – that is, on your face. Who needs 300 lx on the floor when you are trying to remove a speck of spinach from your teeth? We are achieving about 70 lx on the vertical surfaces and most of that is by inter-reflection from the floor and walls. A dark coloured floor would halve that value.

Again, I have used fairly wide-angle lamps but the illumination still isn’t very uniform. You can see that some washbasins are brighter than others. Narrow spot lamps would make things even worse.

And while halogen has great colour rendering, that’s not much use if your face is in shadow.

Tech spec
Luminaire 50W MR16 tungsten halogen downlight
Optical Dichroic 38-degree reflector
Arrangement Three rows of five with two more over the cubicles, a total of 17
Average illuminance at wash basin level 300 lx
Average vertical illuminance on long wall 70 lx
Luminaire efficacy 17 lm/W
Electrical load 850W
Typical cost £340 for 17 units (plus installation)
Pros Cheap and gives good colour rendering
Cons Poor visual effect, dark ceiling, heavy on power, and the short lamp life means high maintenance costs

This option uses Trilux’s Athenik Ligra, a 2,000 lm package recessed LED downlight. There are a few versions, but I like the square one with bezel the best.

The 3000K warm white version gives a light suitable for bathrooms. Always check the colour temperature of LED luminaires before buying – LEDs give more light output at higher colour temperatures, but that cool white light can feel unkind when looking at your face in the bathroom mirror.

The wider beam of the Ligra means it is more uniform and less contrasty than the halogen. But the best thing is the 70 per cent reduction in energy consumption. We are also using just seven downlights instead of 15 in the main area.

To add interest and improve vertical illumination, I have added an accessory in the form of an acrylic cylinder. This adds some sparkle and puts more illumination on people’s faces.

Tech spec
Luminaire Trilux Athenik Ligra CO5 LED 2,000 lm warm white
Optical Aluminium reflector and cylinder accessory
Arrangement Two rows of three, with one extra at cubicles
Average illuminance at wash basin 265 lx
Average vertical illuminance on long wall 70-80 lx
Luminaire efficacy 70 lm/Wcct
Electrical load 230W
Typical cost £1,450 for seven (plus installation)
Pros Attractive, low running costs, efficient white light with good colour rendering. IP54-rated for protection against dust and splashes
Cons Not a particularly imaginative solution

This option gives much the best visual effect and is a completely new approach to bathroom lighting. The Acuro is a traditional T5 luminaire that has been re-engineered by Trilux to suit LEDs. I have used the standard version with white 3000K LEDs. This unit actually costs slightly less, per luminaire, than the Athenik product used above, but I have used more of them to emphasise how much better vertically-mounted luminaires can be.

My main reason for using this unit is that by mounting them either side of the mirrors, we
double the vertical illumination, although the amount of light on the floor is slightly less. The light is a good colour and the illumination is where you want it. The fine-grain diffuser emits a soft, uniform light and doesn’t have the LED hotspots you get
with cheaper luminaires.

A more exciting version of the Acuro is the Acuro Active which contains 3000 and 6500K LEDs that change colour temperature and lumen output over a 24-hour period. In the early hours it emits a low level of light at 3000K. From about 6am, the output increases and so does the colour temperature, reaching maximum light output in the middle of the day, at a cool 6500K. It then dims and warms again, reaching a steady state around 6-8pm. The changing colour temperature is set to match our biological rhythms so we are at our most alert during the day, moving to a calmer mood as night falls.

Tech spec
Luminaire Acuro S
Optical Lensed 3000K LED with opal acrylic diffuser
Arrangement Vertical between mirrors and over cubicles
Average illuminance at wash basin level 143 lx
Average vertical illuminance on long wall 140-150 lx
Luminaire efficacy 80 lm/Wcct
Electrical load 210W
Typical cost £2,660 for 14 (plus installation)
Pros The best vertical illumination by far. Soft in appearance. Long life and low maintenance.
Cons You’ll need more luminaires if you want high illumination on the floor