SUSTAINABLE BUILDINGS


effectively than complex manufactured and engineered products. Small plants near windows can obviate the need for blinds and still provide the benefits of a view.


Evapotranspiration (the process by which water moves from the soil, via the plant and from the soil surface into the atmosphere through evaporation and transpiration) is also an important factor. As water evaporates in the air and is released through pores in the leaves of plants, cooling takes place. The rate of evapotranspiration is governed by light levels, temperature, relative humidity, air movement, plant species and size. Heat energy is used to drive the process, but the precise scale of the effect is difficult to predict indoors as factors such as air flow vary considerably. Nevertheless, large-scale interior planting in atriums will have a measurable effect on temperature as has been demonstrated in several buildings around the world. This process can also help to keep the air in buildings fresh and at the optimum humidity level of between 40% and 60%. Experimental data from several studies over the last few years has shown that interior plants can increase humidity in offices by as much as a fifth, although air-conditioning systems sometimes act in opposition and remove any excess humidity.


INDOOR AIR QUALITY Reducing dust


Research in the USA has shown that buildings with interior plants have less airborne dust than those without. The research (carried out by Lohr and Pearson-Mims) suggests that by adding foliage plants, the accumulation of dust horizontal surfaces can be reduced by as much as 20%. We are unsure about the precise mechanisms at work, but increased humidity and electrostatic effects are suggested as ways by which dust can be reduced by attraction and adherence to leaves.


Carbon dioxide reduction Elevated concentrations of CO2 are


known to induce drowsiness and the consequent reduction in concentration and productivity. Unless indoor air can be continuously refreshed, human activity in modern, well-sealed buildings can result in surprisingly high levels of CO2


. Plants Dust deposition


naturally extract CO2


during


photosynthesis and replace it with oxygen. Research to date suggests that bushy plants with a high photosynthetic rate are particularly effective. Precise calculations on the capacity of interior plants to remove CO2


are difficult


due the large number of variable factors. However, recent research carried out by Prof. Margaret Burchett et. al. at the University of Technology, Sydney, and newly-published data from the University of Georgia has shown that indoor plants can reduce CO2


offices. VOC reductions


The work of Bill Wolverton, both during his time with NASA and afterwards is among the most frequently quoted in plant benefits research. His lab-based experiments showed that plants can absorb pollutant gases such as formaldehyde, benzene and


trichloroethane (known as volatile organic compounds, or VOCs) from the atmosphere. More recently, Margaret Burchett and her team have carried out studies under much more realistic conditions in real offices with typical interior planting densities and have demonstrated that several common species of interior landscape plants have the ability to remove VOCs, sometimes in the order of a 50% - 75% reduction in concentration of total VOCs. The mechanism might involve an interaction between the plant roots and soil microbes.


COMFORT Acoustic benefits


Interior plants have an impressive ability to multi-task. As well as looking beautiful, improving indoor air quality and helping to regulate the indoor environment they can reduce noise levels in buildings, thus reducing the need for expensive (and less beautiful) acoustic panels.


concentrations by 10% in


Ambius’ own research, and that carried out by Peter Costa at South Bank University in London, indicates that plant displays are effective at absorbing, diffracting and reflecting sound. The balance varies with the frequency of the sound and the room’s physical properties. The type of plant, its size, shape, the container, top dressings and the compost all have an effect on the sound reducing capabilities of plant displays. Plants with large, fleshy leaves are better at absorbing sound, whereas those with lots of small leaves are useful as they scatter and diffuse sound.


How to use plants to reduce noise? • The bigger the better. Large plants (or lots of smaller plants) in big containers, which contain more compost and top dressing, (both of which have a significant effect on noise reduction in their own right) make a larger impact on the room acoustics.


• Use a mixture of different plant species and sizes. Experiments have shown that arrangements of


PUBLIC SECTOR SUSTAINABILITY • VOLUME 1 ISSUE 3 29


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