Covered walkways are one of those things you don’t notice until you start looking – then you see them everywhere. The obvious place is supermarkets, leading from the car park to the store. Hospital complexes use them to link buildings. They are also common in apartment blocks and factory estates.
The main difference from a corridor is that, being outside, much lower illumination is needed. Also, the “task requirements” of walking or pushing a trolley are pretty minimal. The main consideration from a design aspect is ensuring that the walkway does not appear too dark when entering it from a brightly lit interior. EN12464-2 only requires 5 lx, but 50 lx seems more realistic for most applications. My design achieves 50–100 lx.
The other aspect is that good vertical illumination is required to light peoples’ faces. This tends to favour using overhead luminaires rather than low level units such as bollards. Another reason for not using bollards is because they could easily be damaged by trolleys.
PIR detectors that switch the lights on when someone approaches are sometimes used to save energy, but remember that people can be wary of entering a dark pathway. A better technique is to set the luminaires to dim to a low level when no-one is around.
We have chosen a typical length of walkway about 30m long and 2m wide, split into bays of about 4m.
This is good example of why the T5 lamp is so ubiquitous. It has the lowest energy consumption and lowest capital cost. Trilux’s Oleveon fitting has a polyester body with stainless steel fixing clips and an optional polycarbonate cover lens. The optics are pretty simple but so is the “task” so nothing complex is required.
Due to the wrap-around diffuser, there is good vertical illumination. The sides of the pitched roof are also well lit.
In terms of energy, cost and function, this solution ticks all the boxes. However, the disadvantage of this option is its rather utilitarian appearance. If you tucked the luminaires into the ridge of the roof, they would be almost unseen.
Luminaires Oleveon IP65 ceiling-mount 28W T5
Optical control Prismatic polycarbonate cover
Arrangement One per bay
Average illuminance Eh on path 93 lux, Ev at head height 100 lux
Electrical load 6.5w /linear metre
Typical cost Budget option
Pros Good horizontal and vertical illumination at low cost
Cons Maybe too dull an appearance
This option uses a surface-mounted, wide-angle downlight with a compact fluorescent lamp. The Onperla’s body is powder-coated aluminium so it is well protected for most outdoor environments. The luminaires are spaced every couple of metres giving just less than 100 lux at deck level. Since we are using two per 4m bay, you can simply save energy by switching them alternately at certain times of the evening or when there are few people around.
The reason for using the Onperla is that it has a quality build and appearance and so is more suited to upmarket retail locations. It’s an attractive unit and adds some interest to the walkway. A possible disadvantage of this type of solution is that it doesn’t put any light on the roof. Although there is a fair amount of vertical illumination on vertical surfaces, there is less than the other solutions.
Luminaires 14 x IP65 Onperla ceiling mount with 18W CFL
Optical control High spec reflector with opal cover
Arrangement Two per bay
Average illuminance Eh on path 94 lx, Ev at head height 60 lx Electrical load 10W/linear metre
Typical cost Mid-range
Pros Looks good
Cons Shorter lamp life than other options
As an alternative to roof-mounted units, I have used direct/ indirect LED units mounted on the support posts. This gives a lot more interest to the appearance of the walkway with broad pools of light on the pitched roof and the pavement.
Due to half the light emitted from the luminaire being reflected off the roof, this solution gives the best vertical illumination on peoples’ faces. Staggering the arrangement lights the full width of the path. There is a slight reduction in horizontal illumination compared with the other schemes (75 lx compared to 90–100 lx) but this is still more than sufficient.
Of course, the big advantage of this scheme is the reduced maintenance due to the long life of the LEDs. Apart from cleaning the surface of the upper glass lens, nothing else should be required.
Luminaires Skeo IP65 direct/indirect LED wall light
Optical control Wide or narrow angle reflector, toughened glass cover
Average illuminance Eh on path 75 lx, Ev at head height >100 lx
Electrical load 8W/linear metre
Typical cost Premium
Pros Least maintenance, most interesting visually, best illumination on people
Cons Initial cos