In the competition for space in our cities, more and more open areas are becoming covered. This leads to buildings being extended over what used to be open pavement. These areas come in all different shapes and sizes and there are thousands of them in our towns and cities. We have chosen an arched colonnade as a typical example.
Being outside, the surrounding illumination level, even in a city, is much lower than indoors. This means that much lower levels can be used within the walkway than would be the case for an indoor corridor. Apart from avoiding obstacles on the ground, the “task requirements” of walking are minimal. However, it is important to provide a good level of illumination on people’s faces so you can recognise them easily.
As well as good vertical illumination, the main consideration from a design aspect is ensuring that the walkway does not appear dark in comparison with its surroundings. Some national standards such as EN13201 and BS 5489 only require 5 lux for purely pedestrian areas, but 50 lx, or more, might be more appropriate for a busy city centre. You also need higher illumination levels where people enter from a brightly lit interior such as a shop or office.
Providing good vertical illumination on people’s faces tends to favour using wide angle luminaires – a very narrow downward beam produces shadows under your nose!
But that isn’t the only solution. Reflecting light off the roof can give excellent results because it “lifts” the height of the space and gives good uniformity. Reflecting light off the roof may be useful where you cannot recess the fittings or where the ceiling height is low.
Wall mounted uplights or combination of up/down work very well. Linear lighting in coving is another good solution if the architecture allows it.
The walkway has a floor to ceiling height of about 3.5m and is about 25m long.
You don’t see much catenary lighting in the UK but it is much more popular in mainland Europe. It is an effective way of providing long, narrow beams of light (I.e a typical streetlighting type of distribution) and the luminaires are mounted directly over the pavement/roadway.
We have used an optic with a high angle 70 degree beam in order to light the walls and pillars as close to the roof as possible. You could achieve a higher horizontal level of illumination at ground level by using a 60 or 65 degree beam but this would be at the expense of darker regions high up.
You can see that there is good vertical illumination on people’s faces and the light reaches almost all the way up to the arched ceiling.
Tech spec A
- LuminairesRFS500 series catenary
- Optical controlCAD-Optimised LED Lenses with toughened safety glass
- Arrangement 6 No at 6m spacing at 2.8m mounting height
- Average illuminance at ground level 72 lux
- Electrical load 24W per luminaire
- Pros Walls, ceiling and pillars are all unobstructed.
The advantage of this arrangement is that it is very unobtrusive. By day, the luminaires would be almost invisible. It is also very easy to install; there is just one supply cable looping the luminaires together.
Another advantage is that the ETV100 luminaire has five different optical distributions. This means you can achieve exactly the right degree of modelling on the stone wall. Light is reflected from both the wall and the arched roof and so there is good all round uniformity and visibility.
From a design perspective, it gives an intimate feel to the space.
Tech spec B
- LuminairesETV100 recessed inground
- Optical controlCAD-Optimised LED Lenses with 5 tonne safety glass
- Arrangement 17 No at 1.45m spacing
- Average illuminance at ground level 92 lux
- Electrical load 30W per luminaire
- Pros Unobtrusive
Uplighting from pillars is another good solution where you want to highlight the ceiling. A light, diffusing surface ensures good uniformity and vertical illumination. There is also an attractive rhythm to the scalloping.
The PIA230 has a choice of three optical distributions so you have wide, asymmetric or forward throws. We have used the forward optic so that the full width of the roof is illuminated.
This uplight is useful in small spaces because the whole luminaire only projects 620mm from the pillar. Again, the light output of 3,000 – 4,500 lumens means you can use it at low mounting heights.
Tech spec C
- LuminairesPIA230 wall mounted uplightOptical controlCAD-Optimised LED LensesArrangement 8 No at 3.5m spacing and 2.2m mounting heightAverage illuminance at ground level 53 luxElectrical load 24W per luminaire
- Pros Makes a pleasing pattern.