Going [Leafy] Green – inside and out

David Baggs, CEO and Technical Director

Background

A building without green life is a building that's letting both its occupants and the wider community down. Plants installed not just in but on contemporary structures produce a wide range of benefits.

The US Green Building Council's LEED Green Building Rating System and the new Abu Dhabi Estidama Building and Community rating tool systems both provide significant credits for implementing vegetated or 'green' roofs. However, at least one green building rating system has credits for installing plants within offices. The Green Star system, by the Green Building Council of Australia, rates buildings on environmental sustainability criteria, and those with suitable plantscaping within them receive points towards the rating also.

Figure 1: The ACROS Fukuoka Prefecture International Hall Green Roof
Source: www.metaefficient.com Architects: Emilio Ambasz & Associates

It's all part of creating a cleaner, healthier environment. Even buildings that are themselves very clean can be affected by VOCs - volatile organic compounds - that people carry into them, such as workers on their clothing, their deodorants, perfume and hairsprays or cleaners with cleaning compounds. Indoor plantscaping can neutralise these and clean up the air in just a few hours. Even carbon dioxide build up can be absorbed and replaced with oxygen rendering the air not just healthier but more conducive to mental efficiency and concentration.

Indoor Air Quality

Worldwide experience has recently been confirmed in Australia by research at the University of Technology, Sydney (UTS) that green plants are an effective way of reducing VOCs in internal air.

The indoor foliage plant species:

• Kentia Palm (Howea forsteriana),
• Peace Lily (Spathiphyllum 'Petite'),
• "Janet Craig' (Dracaena deremensis),
• Devil's Ivy (Epipremnum aureum),
• Queensland Umbrella Tree (Schefflera actinophylla,)
• "Amate' Spathiphyllum 'Sensation', 'Petite' and
• Dracaena marginate

were all tested for their ability to remove VOCs from the indoor air. All seven plant types studied demonstrated benzene removal activity at similar rates. Kentia Palms were found to remove benzene up to 90% from a closed room after 24 hours. When ventilation was added to a room with a Spathiphyllum 'Petite' inside, the rate of benzene removal was improved up to 15%.

Figure 3: Peace Lily
Source: beth.hohertz.org

Studies in Norway and the Netherlands have shown that health complaints at work can be significantly reduced by the presence of plants. Symptoms associated with Sick Building Syndrome (SBS) can be dramatically reduced by the addition of good plant displays. Programmes to extend the use of plantscaping within residential and office situations and further into the retail, healthcare and education sectors would be useful in making indoor air conditions more healthy and improve worker productivity.

There is also a need for more research into the types of plants that are most useful. Encouragement is needed for researchers to look at developing varieties that will not only live well in traditional planters indoors, but also in vertical live indoor and outdoor walls as well as those that live on top of modern-day buildings as green roofs

There are many reasons why the green building rating tools have started to provide significant numbers of credits specifically for green roof.  People are realising that there are thermal benefits, water-conserving and water-quality benefits, and benefits in terms of stormwater detention as well as retention.

Then there's the combined thermal effect of plants when they're on buildings - not just of the plants themselves but of the influence they have on surrounding areas in reducing what's known as the 'urban heat island' effect. Studies all around the world have shown the temperature in built up urban areas are between 3.5°C and 4.5°C higher on average and up to 10°C higher on still summer nights. When there are more plants in urban areas these temperatures drop.

The urban heat island effect creates a 'negative feedback loop' or 'vicious circle': the hotter the city gets the more people use air conditioning so the hotter the city gets as greenhouse impacts increase.

Figure 2: Green roof and walled building in Europe
Source: greenroofs.wordpress.com

The growth in green roofs globally has been phenomenal in recent years as city governments come to understand the full benefits. Germany now has green roofs included in approximately 20% of new buildings and they have been mandated in Tokyo for buildings over a certain size.

Green roofs are even making inroads into the private sector. At the Ford Dearborn Michigan truck assembly plant in the United States, the entire manufacturing floor - 45,000 square metres or approximately 6 acres of it - is under one green roof. Green roofs are already planned in many new developments as the number of companies solely dedicated to their construction increases.

There are 2 basic types of green roof, the traditional 'Intensive' (soil thicknesses over 6 inches or 150mm) more suited to desert environs and the very thin or 'Extensive' roofs- sometimes as little as 2 inches or 50 millimetres to 21/2 inches or 70mm deep overall, plus the plants. When using extensive roofs with very thin growing media there are more restrictions in plant selection and irrigation frequency and as a result there is a need to have an integrated subsoil irrigation system.

The question many will immediately think is 'where will the water come from'? The answer is simple. Along with the many other credits in the green building schemes are credits for water recycling particularly for irrigation purposes. Technically green roofs can be very useful within projects that recycle grey or black water as once these systems are introduced into a project with onsite recycling technology, there is usually a need to dispose of the excess healthy water and green roofs provide the perfect multi-benefit approach to absorbing nutrient laden water than will damage local environmental conditions if disposed into waterways, while providing all the other urban heat island, clean air and visible natural beauty of lush landscapes in new city environs.