Why are we talking about plants in offices?
Its not the first time that we’ve been fascinated with sharing our working lives with plants; most of us have spent time surrounded by dead geraniums sitting on the top of filing cabinets. At a different scale entirely, the Bureaulandschaft movement in Europe, from the late 50s onwards, introduced formal planting into new office developments, much to the delight of plant maintenance companies. We can probably lay the blame on the minimalist design of the 1980s for the decline in pot plants in our working spaces.
Fortunately, the active use of planting in offices was re-encouraged following the work of American psychologist, Edward O Wilson, also in the 1980s. He saw that urban living was creating a disconnect with the natural world, to the detriment to those of us living the urban dream. Perhaps Mr Wilson doesn’t like minimalism.
Today, the Biophilic Design movement is gaining in importance as we consider the parlous state of our health and wellbeing at work. It attempts to rebuild those connections with nature, bred in the human bone millennia ago, to achieve a more positive state of being within our built environment.
Biophilia: love of nature (that’s a human love of nature, of course. If we’d asked the polar bears we may not be in the global mess that we’re in now)
Oliver Heath (Oliver Heath Design) says:
‘Creative use of colours and textures on walls and floors can be the simplest and most practical way to bring biophilic design to life in a project. There are many academic theories that support this, for example the “Savannah hypothesis” outlined by Bill Browning, one of the green-building industry’s foremost thinkers and strategists. The theory states that humans tend to seek out colours which are within the colour palette of nature when it’s thriving. Therefore, the theory follows that using colours within this palette can rejuvenate or inspire us and changing the colour of the walls can be one of the simplest ways to do this.’
And that brings us to The Living Wall
Those early iterations of exploiting plants for human wellbeing concentrated on that emotional connection we all have as nomads trailing across the savannah in search of something decent to eat. Biophillic Design takes us further as research has indicated that greenery can do more than soothe our soul, it can also clean our air.
Research undertaken by universities in Birmingham and Lancaster found that plants in cities are capable of removing nitrous dioxide and microscopic particulate matter (quoted in Air Quality News, July 2012). The researchers found that ‘green walls’ were far more effective in reducing pollution than had been thought. Rather than the 1 or 2% that they were expecting, reductions in pollution more than ten times expectations were achieved.
This shifts the focus onto the ornamental planting that we’ve been used to seeing in our work spaces. Bringing planting at the scale of an entire wall inside a building is a fascinating idea. And if it can produce the same results as those recorded in Birmingham and Lancaster, then we have another job on our hands beyond a watering can. These plants need to be kept vigorous and healthy if they are to function as air cleaners. And that means we need to find a Good Lighting solution.
What do we know about lighting for living walls?
Most of the formal research on artificial lighting for plants has been done for commercial horticulture and that, necessarily, has been focused on food production. While there are obviously similarities between horticulture and ornamental lighting there are also a few important differences.
I need to introduce you to the McCree Curve.
In the 1970s, KJ McCree measured how individual wavelengths of light impacted on plants. He produced a curve that showed the photosynthetic response to absorbed photons. This became known as The McCree Curve – and it looks (unsurprisingly?) like the spectral distribution curve for sunlight. Who would have thought that plants, having evolved on this planet for millions of years would have learned to respond to the only light source that was available for most of that time? The McCree curve can be considered a touchstone in ascertaining the light frequencies that plants need for vigorous growth.
A recent study by Karolina Zielinska-Dabkowska, Julia Hartmann and Carla Sigillo sets the scene for us. ‘LED Light Sources and their Complex Set-up for Visually and Biologically Effective Illumination for ornamental Indoor Plants’ was published on 8 May 2019.
The intention of the Study was to find the most acceptable lighting arrangement that satisfied both plants and humans and to ‘establish relevant sustainable design principles when applying new light sources such as LEDs to illuminate ornamental plants’. At last, flora has a seat at the design table. Hopefully, this means the end of the dead geranium.
The study took a number of lighting scenarios:
- Using standard LED sources at three colour temperatures (2700K, 3000K, 4000K)
- Using single colour LEDs (deep blue; blue; verde; true green; hyper red; far red)
- Using special single-colour LED mixing that approximated to the McCree Curve distribution
- Using special single-colour LED mixing that approximated to a daylight reference.
As far as the human response to these presentations are concerned, we shouldn’t be too surprised to find that the preferred scenario was overwhelmingly for the LED mix that mimicked daylight.
From the plants point of view, the most biologically effective lighting was the scene that mimicked the McCree Curve – again, I don’t think we should be surprised.
And the consequence was . . .
There is an important finding here. If planting, whether as a living wall or in some other arrangement, is to be used for its air-cleaning properties, then its beholden on the designer to ensure that the lighting not only keeps the plants alive, but is capable of providing as much light nourishment as possible.
The study suggests strongly that commercial LED products do not meet that criterion and that planting within a biophilic environment should be illuminated using light sources that are as close to the McCree Curve as possible. And that suggests that we may need to be looking at the latest generation of ultra-high CRI LEDs being offered by Seoul Semiconductors (Sunlike), Nichia (Optisolis) and others.
As always, with anything to do with bio-dynamic lighting, the final paragraph always has to end with -‘more research is needed’ but its to be hoped that, in this case, we may have a positive confluence of technologies; a better understanding of what plants can do – and how they do it, and the continuing improvement in LED performance that is getting us closer to ‘natural light’.
A postscript from Richard Sabin, managing director at Biotecture:
As I am sure you know the McCree curve fluctuates throughout the year and it is the spring or early summer element of this that we want to have really effective internal lighting for plants. This is when the blue end of the spectrum is more dominant. The blue end of the spectrum (spring) is great for vegetative growth (which we want to promote) whereas the red end (autumn) stimulates fruiting and flowering which we don’t want!
It is really difficult to find good lighting companies who are knowledgeable AND commercially oriented. We are still looking….
This story is only just beginning to unfold. Plants, perhaps like us – though we prefer not to recognise it, not only have a circadian rhythm but also have a vitally important seasonal biorhythm. I’m looking forward to seeing what response we might get from the lighting boffins.
The Light Review is a Dissemination Partner for The Biophilic Office at BRE.
Thanks are due to Scotscape Ltd for the use of Living Wall images.