Living walls are an aesthetic delight. But they also provide important services to the environments in which they are situated.

Living walls are an aesthetic delight. But they also provide important services to the environments in which they are situated. “Sick building syndrome”, the well-known condition found in large buildings which re-circulate contaminated air, causes illnesses in workers and inhibits productivity. Living walls refresh air in buildings, effectively counteracting sick building syndrome.

Living walls have been installed in buildings in Europe and Japan for decades. The living walls created by Dr. Alan Darlington, an adjunct professor of Environmental Biology at the University of Guelph (near Toronto, Canada), differ because the air cleaned by his living walls is circulated throughout the air duct system of buildings in which they are situated.

Darlington’s walls have been installed in cafeterias, places of worship, health spas, commercial and industrial properties, and academic institutions – the most spectacular example is a four-story living wall containing 1,000 plants installed at the University of Guelph’s and Humber Institute of Technology in Toronto.

A more profound benefit of living walls is their ability to remove some 200 common indoor contaminants. These contaminants include air borne formaldehyde, benzene, and toluene often found in wood products, furnishings, household and personal cleaning products, paints and solvents. Toluene has been connected to birth defects and retardation in children.

“A living wall can clean up to 0.1m3 air through every 1m2 living wall per second,” according to Darlington. The microbes on each plant’s roots do the actual air “cleaning,” viewing these pollutants as food. Fans, situated to pass air over each living wall, provide the microbes with a constantly renewed source of “contaminated” air. The cleaned air is then taken up through ducts above the wall and circulated through the building’s air system. An ironically symbiotic relationship exists between humans, their pollutants, and the living walls. The sustainability of the walls’ environment depends, in part, on the polluting habits of human beings.

Plants for the living walls are chosen based on their ability to remove select pollutants. They are placed in “pockets” at intervals of 1 plant per square foot with each pocket containing a rooting medium less than 5 cm thick which allows for each plant’s roots to be exposed to the air. Ordinary potting soil is not used as it has a tendency to break down too quickly and is prohibitively heavy. Plants are also chosen for their ability to grow in this medium and in the light available, both natural and artificial.

“Vertical hydroponics” is Darlington’s description of his living walls. The plants range from a few inches to several feet in height and are nurtured with a constant flow of water taken up from a reservoir at the wall’s base. The water is circulated across the top and flows down through the rooting medium and the plants’ roots. Ten watts per meter is expended to power the pumps and the same wattage is consumed for the fans; the lights consume approximately 100 watts per square meter. Darlington concludes that the “clean air generated by our system uses up to 60 percent less energy than conventional systems.”

And living walls also contribute to combating climate change. In summer, living walls cool indoor air, reducing the need for air conditioning and its concomitant pollutants and energy use. In winter, the wall’s humidity reduces heating needs. Darlington estimates that the walls save 0.3 to 3.5 kilowatts per person during winter’s coldest period.

Living walls are adaptable to their environments. Potential future applications include installation in: mines, hotels, cruise ships, airports, sports facilities, apartment buildings and condominiums, factories and repair shops, even space stations – anywhere one finds a concentration of people, pollutants, and closed air circulating systems.