Lighting Living Walls: finding the best white light for the job.

I’m sitting at my desk on the hottest day of the year (so far – who knows what might happen between now and Xmas). Where I really want to be is walking in some dense woodland where I can bury my head in the green-leafery, breathing in all that sappy moisture.

Maybe, at the very least, I could have a Living Wall that I could sink my face into – ahh, how lush that would be.

I wrote about Living Walls this time last year (The Biophilic Office: Living Walls) and I’m coming back to the topic now because a new report has been published by Amardeep Dugar, of Lighting Research and Design.

Along with a posse of lighting designers, architects and students, I was invited to take part in the study, back in the depths of last winter – and how long ago and oddly welcoming that feels from here. As we’ve become aware, lighting for Living Walls doesn’t follow the same pattern as lighting for commercial horticulture. The fundamental difference between the two approaches comes down to what we expect from the plants themselves.

Horticulture is a commercial exercise that is designed to promote plant growth and fruit production. We don’t really care what they look like, so the familiar pattern of red+blue LEDs has come to dominate the intensive horticultural sector.

A Living Wall is there for you and me. It’s the nearest we can get to connect with a ‘real’ environment in our urban working lives. A simple analogue would be a wall-wide photograph of a wood, perhaps; a Living Wall brings the reality of the living world into our constructed environments.

Because we’re exploiting the planting for the health and wellbeing that it offers the occupants of an office, the idea of using red+blue doesn’t work. We need ‘naturalness’ – and that means white light. But the plants have demands, too. Some early Living Walls were so badly designed that the ‘living’ part of it was a fiction. The plants died – that’s what they were doing; these were actually ‘Dying Walls’. The building managers just replaced the planting on a regular basis. An appalling waste.

The lighting exercise that Amar and his colleagues undertook was to find out if there is an appropriate balance between plant health and human acceptability. A successful Living Wall is one where the plants thrive – not just survive – in an alien environment.

And now, a shout-out to the team:

  • Morris Costello: Lumempulse AlphaLED, for providing the luminaires
  • David Gilbey: NDY Light for his insightful design input
  • Rick McKeever: of WonderWall, who supplied the plants
  • Peter Raynham: of University College London who managed the research at UCL East in Stratford.
  • Roger Sexton: Xicato, for the ‘Artist Series’ LED light engines within the Lumenpluse luminaires.

If you’d like to read the report: Lighting Green Walls- finding the optimum CCT and SPD of white LED light sources.

Amar says Green Walls; I say Living Walls. He says, tomato; I say tomato.

There were two tests undertaken:

  • what light provided the best growing conditions
  • what light provided the most attractive wall display

There can be so many variables in this kind of research, so it was decided to ‘contain’ the environmental conditions by controlling lighting conditions.

  • Colour temperature: was limited to three conditions: 3000K ( for a warm interior environment), 4000K (as a conventional office environment) and 5600K (as being close to daylight).
  • Colour rendering (SPD): was based on TM30 Colour Fidelity (>93) and Colour Gamut (>101) for all three colour temperatures.
  • Illuminance: 1200Lux (approx) at the top of the wall, falling to 500Lux (approx.) at the foot of the wall.
  • Illumination times: 12 hours ON at 100% and 12 hours OFF, at 0% – for a period of 5 months.
  • Plant selection: not all plants are the same. Six types were selected – not all survived.

And the outcome:

One thing that pointed a questioning finger at previous Living Wall assumptions was the effectiveness of the selected illuminance levels. Plant health and growth patterns was generally supported by the chosen illumination strategy, undermining the suggestions that illuminance levels above 10,000Lux was necessary.

On the ‘naturalness’ scale of human acceptance, the results tended towards 4000K.

As for the plants, lighting at 3000K produced leggy and weak stems; 5600K, as might be expected from previous research,  displayed the shortest and strongest stems.

What needs to happen next:

Will it be possible to create a lighting environment that enables plants to benefit from 5600K for some part of the day, while functioning at 4000K during hours of human occupation?
And a begged question here: does it really matter if we, mere humans, have to put up with a Living Wall lit at 5600Lux if that is delivering the best light for the plants?

More work needs to be done on more plant types, seeking the more robust species for inclusion in future Living Walls. This sounds like an eminently practical thing to do that deserves to be supported (and funded)  by the designers and builders of Living Walls.

And finally – does the general public see the lighting of Living Walls differently to experts in the Built Environment? Do we really need to find out?


By the way – while we’re talking about Living Walls in particular and living greenery in general . . . why not enjoy the real thing and get involved in Forest Bathing.

And if you’d like to connect with the living lungs of the planet, you can contact my very good friend Sara Greenwood. who is a Forest Bathing Leader.

Just get out there and hug a tree – hug several!


Biophilic analogue: Green Trees Forest wall mural wallpaper from ICON


(Thanks to Sage Greenlife for use of the banner image)

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