Floodlighting a building façade is a classic case of ‘it’s not about the numbers’. Of course, you can always calculate the vertical illuminance, luminance and uniformity values for a building but that’s not the primary goal.
There are many non-engineering decisions to be made. Do you want the building to stand out or blend in? Do you want a subtle or ‘in your face’ effect? Which parts of the building are worth highlighting? Do you want colour? (My default answer to this question is no – IMHO, colour on buildings is more often blight than benefit.)
Making the building look good is down to aesthetic judgement. If you are unsure, ask a lighting designer, architect, planner, or local conservation groups about the effect they would like achieved.
Remember, you can save a great deal of energy by highlighting certain parts of a building rather than flooding the whole façade with uniform light. Similarly, switching off the lights when no-one is around can halve your energy cost.
Here, we show three different approaches. The illumination level required would depend on the location of the building. Decide on the effect first and crunch the illumination numbers after.
The building is 12m high and 24m wide, with the same light over the doorway in all three versions, for security reasons. I’ve used various fill-in lights for the central area, and some of the internal lights are on and some are off, which is what happens in real life.
All the products used are from Kingfisher Lighting (mostly from their Arcluce range), who have a wide range of products for exteriors.
Light the recesses
If you have a regular pattern of windows in your building, one approach is to use linear LED luminaires in the recesses. This works especially well if the façade is uninteresting or you are not allowed to mount luminaires on the external face.
The effect is that the building is seen as a regular pattern of illuminated shapes and the façade itself is comparatively dark. It works less well if there is a high level of ambient light such as from streetlighting.
The windows are fitted with the Krio linear LED strip. This comes in two basic lengths, 680mm and 1360mm, consuming 24W and 48W respectively. Don’t forget that you can always dim the LEDs if they are too bright for the location or size of window. This has the additional benefit of saving energy. There is a choice of beam widths so you can choose the most appropriate one depending on the proportions of the window. There is a walkover version of the Krio for mounting in the pavement.
Note that you can’t light the glass itself. It is the brick recess, mullions and transoms that are illuminated. Drawing down the blinds inside will give an even bigger impact and prevents passers-by seeing inside.
- Luminaires Krio LED
- Optical control Lens
- Electrical load Approx 35W per linear metre
- Pros Works very well with regular arrays of windows
- Cons You need a fairly deep recess
- Price range Medium
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Up and down
Kingfisher’s Tula is a surface mount wall unit which directs narrow beams of light up and down. This type of luminaire is commonly used both inside and outside where there is a series of arches or vaults.
I have used them here to emphasise the symmetry of the building. Unlike option 1, the pattern of light is seen on the surface of the façade rather than the window recesses. This technique works especially well with rough surfaces such as brick. The ground floor has a totally different architectural style and here I have located the Tula in the tall window recess to emphasise its height.
It is purely a matter of personal taste whether you would mount them in the recess or outside. One nice aspect of this unit is that it is available in a range of colours and there are a variety of beam widths up and down.
- Luminaires Tula wall mount up/down
- Optical control Lensed LED
- Electrical load 7W per luminaire
- Pros Makes the building stand out
- Cons Can look too busy by day
- Price range Low
From the ground
This uses all recessed in-ground units. At ground level, I have used the IP67 Inground 350. This is a stainless steel drive-over unit. This is actually a powerful 70W unit but I have dimmed it down since I only want the light to reach the first floor. The wide beam is necessary having the luminaires so close to the building. Always check what is under the pavement. A contractor I know nearly pierced the roof of a disused cellar – no-one knew it was there.
In between the windows are the Moto floodlight with a 20° beam. This can have integral or remote gear depending on how much space you have available. There is a wide choice of beam spreads.
Finally, on the fourth floor are little Tito spotlights. These are much lower power than the Moto but I have used them because there is less height to illuminate. It is also a good idea to illuminate buildings so that the illumination level fades from the ground level to the roof. This will emphasise the height of the building or structure.
This option would suit a city centre location where there is a high level of ambient lighting.
- Luminaires Various in-ground units
- Optical control Lensed LEDs
- Electrical load From 5W-40W per luminaire
- Pros Useful where you don’t want any obstructions above ground
- Cons Make sure you can mount them in the ground
- Price range High