Extract from the April issue, by Gabrielle Stannus

Recent research conducted by the University of Technology Sydney has shown that active green walls can significantly reduce indoor air pollution, thereby reducing the incidence of Sick Building Syndrome.

Sick Building Syndrome (SBS) can impact severely on productivity, sick leave and quality of life. Symptoms include headaches, dry throats and fatigue. SBS is thought to be caused in part by gases emitted by synthetic items, such as computers and carpets, accumulating inside buildings. Plants can filter out many of these gases and other indoor pollutants using potentially less energy than conventional heating, ventilation and air-conditioning (HVAC) systems. With enough light, plants can remove “stuffiness”-inducing CO2, directly through photosynthesis. Plants may also tracp some particulate fmatter (PM) on therie lefaves, and absorb or adsorb volatile organic compounds (VOCs) to plant surfaces.

In 1989, NASA researchers found that the plant root-soil zone appeared to be the most effective areas for removing VOCs. Recent work conducted by Dr Fraser Torpy and the University of Technology Sydney’s (UTS) Plants and Environmental Quality Research Group has shown that air exposure to the plant root-soil zone can be increased by using “active” green walls such as Junglefy’s Breathing (BW) system.

The BW uses a small fan to pump indoor air through the plants and their growth media. The fan system accelerates VOC diffusion into the substrate, where bacteria break them down as a food source. The BW also has the advantage over conventional filters in that its soil bacteria can break down any biodegradable parts of the trapped particles, including most of the dangerous chemicals associated with SBS. Dr Torpy’s team have found that the BW now outperforms the most common air conditioning system filters in removing PM as it is almost impossible to clog up, given its potting medium’s thickness, and the bacteria in it that break down organic materials.

Concerns that green walls may actually increase airborne mould spore loads indoors have not been borne out in UTS’ BW research. This is potentially good news for interior plantscapers installing them in medical or educational facilities. Dr Peter Irga found that the BW made no significant contribution to the density or diversity of airborne cultural fungi in a test room. Few organisms of concern to public health were identified. Dr Irga concluded that well-maintained green walls are unlikely to make hazardous contributions to indoor fungi. However, further work to document the bio-aerosol generation rate with variations in temperature, air flow, plant varieties, planting densities, maintenance schedule, plant age, plant growth substrates and substrate moisture content is needed.

Dr Torpy firmly believes that botanical systems are the way of the future, saying his team continues to conduct plant research because it works. At the time of writing, the UTS team was preparing to run a demonstration in a Beijing classroom with Junglefy’s support. This is the first in-situ experiment the team has conducted since 2006. They are also assessing the BW’s effectiveness as an acoustic barrier and in removing cigarette smoke.

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