Staff costs are typically the highest operational cost associated with most office based businesses yet government statistics show that 25.9 million working days are lost in the UK due to work related illness. The number of working days lost to stress, depression and anxiety increased by 24 per cent between 2009-2014. Mental health now costs the UK economy £70 billion per year. Such statistics are supporting a growing interest in the health and well-being of people at work.
For decades, employers have been seeking ways to improve the productivity of their workforce. Lean office management and minimalist design principles have been applied in the hope of increasing productivity. In contrast, since the 1950s when Maslow observed that aesthetically pleasing spaces have a positive impact on energy levels and wellbeing, research has found there are benefits from enriching the office space with plants. One small experimental UK study showed that when the office environment was enriched by plants and artwork, workers productivity was higher and response times on computer based tests were 12 per cent faster than without plants.
Biophilia, the idea that humans have an affinity towards the natural world, helps explain why connection to nature from within our workplaces is key to supporting employees’ positive mental health. Research has shown that living plants can bring benefits to the physical and mental well-being of building occupants, including noise reduction and health benefits from improved air quality.
Several building rating standards now recognise the value of greenery in the workplace. The WELL Building Standard focuses exclusively on human health and wellness, it requires consideration of biophilia within each project stage to help create calming spaces that quiet the mind and help to reduce long-term stress. The Green Star rating system in Australia gives points for approved indoor plants and some LEED certified projects have gained points for the use of interior plants by showing they improve indoor air quality, reduce the need for cooling and for the biophilic nature of the building.
The psychological wellbeing of a person at work depends on many factors and employee-environment relations are very complex. Although it is difficult to single out the effect of plants, numerous studies exist which show that greenery in the workplace can reduce the stress levels and improve the mood and concentration of building occupants. Studies based in large open plan offices in London and the Netherlands found that enriching a lean office with plants significantly increased workplace satisfaction, concentration and perceived air quality and lead to a 15 per cent increase in productivity.
A survey of 385 Norwegian office workers found the presence of plants was associated with lower levels of sick leave and increased productivity. The size and the location of the plants was found to be important; for example should plants be located in the work zone of the office, in the rest area or in the reception? Studies of air quality suggest that plants should ideally be within a person’s breathing space zone to be effective for air purification. The majority of people now spend around 90 per cent of their time indoors, where pollution levels can often be higher than outdoors. Indoor air quality has become a major issue in recent years having a significant impact on the health, wellbeing and productivity of office workers. Significant advances have been in mechanical ventilation systems but living plants can also improve air quality by adding oxygen, increasing humidity and removing pollutants.
In poorly ventilated rooms, as people exhale, the concentration of carbon dioxide (CO2) in the atmosphere increases. High levels of CO2 have been associated with headaches, drowsiness and reduced decision-making performance. Plants through photosynthesis, take in carbon dioxide and release oxygen into the air and studies in experimental chambers have shown that plants can remove CO2 even at the low light levels associated with offices. The removal rate depends on the quantity of plants, the species, leaf area and light levels. Much further research is required to assess the effectiveness of different plants in real office environments.
The indoor air within offices can frequently feel dry with low relative humidity, which worsens in winter when the heating is on. It can cause irritation to the eye, nose and throat membranes, making people more susceptible to airborne viruses, chemicals, mould spores, dust and allergens. Plants, through respiration, can raise humidity levels to a more comfortable level and a two-year study of 60 office workers in Norway in 1995-6, found that the presence of plants in the workplace reduced the ailments of fatigue, headache, sore throat, cough and dry skin by between 20-45 percent. Humidity levels above 70 per cent also cause indoor air quality problems.
In the 1980s NASA scientists planning for a space station on the moon, recognised air quality was a major concern and they measured over 300 volatile organic compounds (VOCs) in the air within the spacecraft during occupancy by its crew. VOCs are a group of chemicals including formaldehyde, xylene, toluene and benzene, emitted as gases from human bioeffluents and products such as paint, building materials, furnishings and office equipment. Some VOCs such as benzene, can have serious adverse health effects and VOCs have been associated with sick building syndrome. Concentrations are consistently higher indoors (up to ten times higher) than outdoors. While opening windows or naturally ventilating indoor spaces can reduce VOCs and alleviate some of the symptoms, this is not always possible.
The NASA scientists discovered that houseplants could remove VOCs from the air inside sealed chambers. There is now a significant body of work proving that plants can remove VOCs through their leaves and through the micro-organisms found in their roots and the soil. The rate at which plants can remove VOCs depends on the plant species, light intensity, growing medium and the type and concentration of VOC.
Plants can be introduced into the office space as individual potted plants, large scale interior arrangements and indoor green walls are becoming increasingly popular. Green walls being vertical structures contain a large amount of plants but take up less floor space than planted arrangements. In addition to the other benefits, green walls can reduce noise by up to 40 per cent depending on the type of plants and growing medium.
Both planted arrangements and green walls have installation costs and ongoing maintenance requirements, usually from professional horticultural services. A cost-benefit analysis of greenery in the workplace would be of great interest but no published economic studies have been found.
The overall findings from the body of scientific research indicate that greenery in the workplace has the potential to support a healthier, happier working environment for employees and a more productive business for the employer. But more research is needed to verify the findings from experimental studies in real workplace settings, to identify which plants to use, where to locate them and to determine the cost benefits.