Green buildings: the role of interior plants

The Green Building movement is gaining strength in many countries. Developers, especially governments and local authorities, often set the trend by commissioning buildings built to recognised ‘green building’ standards.

The main motivation in building to such standards is that ‘green buildings’ are much more energy efficient than conventional buildings and, consequently, cost less to run. However, there are other factors that motivate developers to adopt ‘green building’ standards, including a desire to enhance their image as responsible corporate citizens or employers, or to increase the lettable income from the buildings.

Interior plant displays can contribute to a good green building rating in many ways, not all of which are immediately obvious.


What are ‘green buildings’?

‘Green buildings’ are buildings that have been built or refurbished to a set of auditable standards that reduce the negative impact of the building on the environment. Initially seen as a ‘nice to have’ feature, developers are increasingly specifying that buildings should be as environmentally friendly as possible.

The standards, or rating systems as they have become known, have been developed by a range of different organizations. In the UK, the Building Research Establishment developed BREEAM, the BRE’s Environmental Assessment Method in the 1990s, and this has become a model for green building rating systems in many other countries. In the UK, it is estimated that as many as 20% of new office buildings are built to BREEAM standards (Advanced Buildings Newsletter 22, 2000). In North America, the United States Green Building Council (USGBC) is a not-for-profit body set up just to promote the ideals of green architecture. Similar organisations exist in other countries, including Australia (e.g. Australian ‘Green Star’ system ), Spain, Canada and South Korea and they often work together to develop rating systems appropriate to the different locations.

As technology and interest in green buildings has developed, the rating systems have been updated, refined and even expanded to take into account different building types. They have also been expanded to take into account other factors that can only really be considered ‘green’ in a much broader sense, such as the quality of the work environment that has more to do with good workplace management practice than the conservation of resources and protection of the physical environment.

What are the benefits to the developers and operators of green buildings?

Energy costs
Buildings that comply to green building standards are built or refurbished with energy conservation in mind. Intelligent design can reduce energy consumption considerably.

Productivity and absenteeism
Sick Building Syndrome is a term used to describe buildings where there are high levels of complaints about the indoor environment. Often these complaints relate to poor control of heating, ventilation, humidity and lighting, particularly at a local level. Other contributory factors are noise and uniformity of texture and colour (something that can easily be cured by the presence of well-designed plant displays). Green buildings, by their nature, rely on natural ventilation and high autonomy over the control of the working environment. Absenteeism rates have been shown to be reduced by as much as 6% in naturally-ventilated buildings. Productivity gains have also been shown in buildings where there is a greater access to natural daylight (and those, such as in Norway where artificial daylight has been incorporated). To develop this to its natural conclusion, good office design and green buildings should help employers meet their obligations to provide a safe working environment.

Improved lettability
Building owners are in fierce competition to find occupiers for their properties and in a market where office space is not in short supply. The cheaper running costs, improved working environment and ‘feelgood factor’ that attaches to green buildings make them more attractive to potential lessees.

Staff pressures / recruitment / retention
In an economic climate, such as that which exists in the UK (and the South East of England in particular) where there is real difficulty in recruiting and retaining well-qualified staff for knowledge-based businesses, the quality of the working environment becomes much more important than it did a decade or more ago. Office workers now expect high quality workspaces and are beginning to ‘interview the building’ when considering where to work. If companies wish to attract high quality employees, then they have to provide a good working environment for them.

Government pressure / incentives
In most locations, the development of green buildings is driven by the factors stated above. However, there are some instances where the development of green buildings is actively encouraged by government. Canada is perhaps the best example so far. The Canadian Government’s Commercial Buildings Incentive Scheme awards up to Cdn$60,000 to developers that satisfy certain green building standards (mainly relating to heat, light and water management). In Australia, the government of South Australia are attempting to lead by example and have stated that all new office buildings that they occupy will have a ‘Green Star’ rating of at least 5 stars. Australia also has a number of funding opportunities to encourage developers to reach ‘Green Star’ standards.


Where do interior plant displays fit in?

The above are all very worthy and make good sense, but how does interior landscaping fit in and contribute to the ‘greening’ of a building (apart from the literal effect caused by presence of foliage)? In all the cases listed below, plants have a useful role to play.

Alternatives to manufactured / engineered solutions
Even though plant displays are the result of an industrial process, their production and use has a significantly lower environmental impact than most manufactured or engineered solutions (see our article on the environmental impact of interior landscaping in our on-line learning programme). The right selection and care of plants in a building should not result in any significant use of resources in the building and should not contribute significantly to running costs, especially if other ‘green building’ initiatives are in place. Also, plant displays are usually significantly cheaper than manufactured items and they often fulfil more than one function. An office divider can do little more than divide a space, but a plant doing the same thing will also be reducing noise, collecting dust, humidifying the air and removing some pollutants. Plant displays can be especially useful aids in space management in commercial buildings. They can form natural screens and partitions, ideal in open plan settings, and help guide people around a space.

Use of grey water and rain water
Grey water is that which has been used once, for instance to wash hands or dishes, and then recycled for re-use where drinking quality is not required, e.g. toilet flushing. Grey water is usually treated in some way to remove particles and is often sent through a reed bed where biological processes help with the degradation of materials such as detergents. Once treated, the water is reused for applications that do not require potability. Grey water is, in most cases, suitable for watering both indoor and outdoor plant displays.

Rain water is a free resource that is seldom exploited. Many commercial buildings have large roofs and other surfaces that would be ideal for capturing rain water. This water could be used in the same way as grey water and would be ideal, if not beneficial, to interior and exterior plant displays.

Cooling
One of the benefits claimed for interior plants is that they help cool the air around them through evapotranspiration. The effect is genuine, but limited as in most cases, rates of evapotranspiration in offices are low due to limited light and humidity. However, atrium planting can certainly help with temperature regulation in some buildings and there are a few examples of buildings that incorporate plants for that very reason (e.g. the library in Herten, Germany; Commerz Bank, Frankfurt (shown here); ING Headquarters, Amsterdam).

(Photographs: Gabriele Röhle, Commerzbank AG)

Dust reduction
Research carried out in the USA has demonstrated that plants attract more than their fair share of dust and that particulate levels can be reduced by as much as 20% in some situations. This would mean that the use of air cleaners could be reduced (although not eliminated) in such places.

Volatile Organic Compounds (VOC) reduction
As well as the notorious studies carried out by Bill Wolverton in the USA resulting in claims for miraculous abilities of indoor plants, there is now a body of research from Dr Ron Wood of the University of Technology, Sydney that shows that plant root / soil microbe systems are effective at removing a range of VOCs at relatively low planting densities in realistic building situations.

Noise reduction
Studies carried out by Rentokil Initial's Research and Development department, and those conducted by Peter Costa with our support have demonstrated that plants can be effective at reducing background noise. Species selection and positioning are crucial to make these effects work.

Alleviation of Sick Building Syndrome and improvements in well-being
Studies in Norway and the Netherlands have shown that health complaints at work can be significantly reduced by the presence of plants. Whether these effects are physical or psychological (or a combination of the two) is uncertain. What is clear, though, is that symptoms associated with Sick Building Syndrome (SBS) can be dramatically reduced by the addition of good plant displays.

Alleviation of Sick Building Syndrome and other problems in deep plan buildings
Office buildings with large floor plates and deep plans have a number of problems and they are seldom ‘green’ buildings. This is because they are difficult to ventilate naturally and there is limited access to natural light and views. Buildings such as these are ideal candidates for ‘greening’ with plants. As well as the benefits described above, planted atriums are useful as alternatives to views of the outside world, and the combination of plants and artificial daylight can help overcome the problems of lack of access to natural daylight.

Part L of the UK building regulations on energy efficiency
Part L of the UK building regulations relate to energy efficiency and one consequence may be that office buildings will be constructed with fewer windows to reduce heat loss. This may mean a loss in amenity for the office workers in such buildings as access to views and natural light will be curtailed. Here is another instance where good interior plant displays can help to remediate the problem.

Conclusions

Developers, architects and building managers now have another tool in their inventory of green building solutions. Whilst plants on their own can not make a building 'green', when they are used intelligently and with imagination, they can certainly help. Can a building be really 'green' without interior plants?

Author: Kenneth Freeman