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Focus Archive

Plants and the Indoor Environment

December 1998
John Manos & Jan Traeger-Synodinos

The guest contributors to Focus this month are John Manos and Jan Traeger-Synodinos.

For the majority of north Europeans, the "work environment" means an office, generally for eight hours a day, five days a week. Since safety risks are few, issues such as ergonomics, lighting, heating and ventilation are increasingly the preoccupations of safety and employee welfare specialists, facilities managers and engineers.

This trend was well-illustrated at last year's biannual A+A safety exhibition in Dusseldorf where, among the numerous side-meetings organised by BASI[1], the single most popular seminar was concerned with the indoor environment in general and possible advantages of incorporating plants and vegetation in offices to improve the quality of the indoor environment.

The conclusions of the meeting were that the display of plants in offices may have a positive effect on occupants by acting at two levels: - through their positive psychological response to planting/vegetation: i.e. a positive reaction and feeling of well being, reduction of feelings of stress, etc; but also - by achieving physico-chemical effects on the indoor environment, through air scrubbing, humidification, temperature control (shading and evaporative cooling) and acoustic improvements, thus reducing the negative health effects often reported in poorly controlled indoor environments.

Four presentations made during the one-day seminar dealt primarily with psychological effects while two were equally concerned with physico-chemical aspects.

Psychological effects of office planting

British architect Jane Stiles looked back through history and described how the use of decorative vegetation had developed from the use of container-grown plants to decorate terraces in China 3,000 years ago, and in the Hanging Gardens of Babylon (810-84 BC), to their first use in inner courts of Egypt in 300 BC and Pompeii 2,000 years ago.

The pioneers of house plants in the 19th century were the Americans and lower middle classes of Europe, Stiles said; and the modern house plant first appeared at the end of the 1940s along with wider use of central heating. By the 1960s house plants and modern interior design had become inseparable. Plants in offices, however, first appeared later, between 1965 and 1975, when standards of office accommodation improved. To investigate the nature of psychological response of building occupants to interior planting, Stiles carried out a number of questionnaire surveys.

Her results showed that the presence of plants encouraged people to make greater use of "planted" areas in buildings and helped reduce feelings of stress, but in neither case was the effect noted with statistical significance. Tove Fjeld of the Agricultural University of Norway reported preliminary results of a study to investigate the effect of interior planting on health conditions among a small sample of office workers. The study involved what he termed "environmental psychology": it assessed how building occupants evaluated the indoor environment, enquiring about personal health and feelings of well-being. To ensure that the preliminary results are valid, Fjeld said, the study needed to be extended over time.

Roger Ulrich, of the College of Architecture, Texas A&M University, USA, discussed the effect of visual experiences on stress and health indicators. Like Fjeld earlier, he said the theoretical explanation for beneficial effects of visual experiences with plants was the primordial contact with nature and plants which occurred during man's evolution. Ulrich had investigated psychological, physiological and behavioural manifestations of stress and recorded that among stress-reducing factors was viewing settings with prominent vegetation. He said similar effects had been noted in studies of prison inmates and post-operative hospital patients.

Effects on the physical environment

Dutch consultant engineer John Bergs (DHV AIB B.V.) presented a "guide for building managers" which reviewed studies of the effects of both psychological factors and of the physical environment on people at work. He cited results of studies conducted in Dutch offices in which 20% suffered from health complaints that were attributed to "problem buildings", concluding that most of the complaints about the work environment have a direct technical cause which relates mainly to "air quality and comfort in terms of temperature".

The factors that contribute to "healthy building quality", especially relative to the workplace, are multiple and diverse, Bergs said; in particular, besides being well designed, a building must be well managed because "even well-designed buildings can become a problem buildings".

The most broad-ranging and technical presentation was co-authored by Peter Costa, of the consultant engineers Brotchie, Costa and Grant, and Professor Ron James of South Bank University, UK. Their paper described the engineering benefits associated with use of plants indoors; these included: water polishing, shading and evaporative cooling, air scrubbing, humidification, and acoustic improvements.

There was little data available air scrubbing, but Costa said it was clear "that plant leaves, roots, soil and micro-organisms working together in a symbiotic manner" play an important role in the process of removing toxic chemicals from the air. Certain plant species are more appropriate for removing particular chemicals but generally, in closed systems, "plants don't produce anything that the people do not like and people do not produce anything the plants do not like".

Finally, Costa reported that indoor plants had measurable beneficial effects on room acoustics, absorbing, diffracting and reflecting sound. Jane Stiles had opened the meeting by telling delegates that the first plant collectors had selected species as potential sources of food or medicine and only later for their ornamental value. In the last century, the need to maintain plants in unsuitable climates led to Victorian innovations such as glasshouses and conservatories. In the 1990s, it appears, the concept of interior planting may have come full circle, and is now a case of choosing plants to suit and improve the environment rather than creating environments to suit plants.

The full version of this article appears in European Safety News No. 60

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[1] The Bundesarbeitsgemeinschaft fur Sicherheit und Gesundheit bei der Arbeit e.V., in co-operation with Bloemenbureau Holland, Schipolweg 1, NL - 2316 XB Leiden. v.5 - 1367

John Manos
European Editor, European Safety Newsletter
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