Green roof: the environment-friendly urban access to nature
June 20, 2014 00:00 By Supitcha Chaipipat
I would like to bring readers' attention to the issue of environmental care.
It is widely understood that Thailand is a tropical country with temperatures increasingly rising each day, especially in the capital. This is because there are few green areas in Bangkok as compared with the population density. Environmental-awareness campaigning therefore becomes important, and has given rise to the “Green Roof, Living Roof” concept.
This refers to roofing covered with green vegetation growing in proper soil to help reduce heat access through the roof. As a direct benefit, when the first ceiling reduces the heat, the house’s interior will become cool, helping us cut the electricity cost incurred from air-conditioning. Moreover, it can reduce noise from the outside and filter falling dust.
In some places, green roofing is used for increasing space for utilities or living, instead of leaving the deck unused. A green roof also helps maintain the condition of the deck’s floor and the leak-proof system.
However, what makes the green roof really attractive is its positive impact on the environment. First, it can produce fresh air and filter pollutants and carbon dioxide from the air.
Second, it reduces heat reflection on the air and filters pollutants and heavy metals from rainwater.
And third, it reduces the volume of water from the roof to the drainage system, relieves flooding during heavy downpours, and improves the city’s ecology system, as it attracts birds and insects.
There are three types of green roof: intensive, semi-intensive and extensive, depending on the depth of soil and the need for maintenance.
The easiest of the three to build is the intensive type, since it does not need to be beautiful and is lightweight. The vegetation used for this type of green roof must endure harsh conditions such as a shortage of water, and entails the use of mostly native plants that are water-absorbent and can grow in drought.The materials used for gardening, including the water systems, are lightweight. However, the key factors for consideration in building a green roof are as follows.
Before building a green roof, let the engineer check the load capacity of the roof area. Existing buildings and roofs of row-houses in general are made of concrete and can house an intensive green roof without a heavy weight burden.
But to construct an extensive green roof for practical use and aesthetic purposes, with a walking path and a well or tree baskets, one must check the roof’s load capacity to avoid problems in the future.
Choose a type of soil that is light and water-absorbent, which can be easily drained but is not easily degradable. European and American countries, Japan and Singapore tend to build green roofs from readily available soil, and not of the extensive type.
Lightweight soil is suitable for roofs or decks of existing buildings that were not designed to support a heavy weight. This includes decks that are not designed for practical use, such as most of the row-house roofing in Thailand.
A glossy-surfaced concrete deck sealed with a leak-preventive solution, but with proper drainage, in general can house plant vases.
Watering a green roof depends on the type of roofing. An intensive green roof has no water, but the downside is that only one type of plant will eventually survive – that is, the most enduring type – and there is a lack of biodiversity. Therefore, despite the intensive green roof, a water system has to be added for use during the dry season.
However, semi-intensive or extensive types need a water system much the same as landscaped roofing in general.
Landscaped roofing or deck gardening has been familiar in Thailand for some time, but only for aesthetic and practical purposes, and not for heat reduction through the roof. However, the roof garden functions in much the same way as a green roof as an energy saver.
Currently, no major housing projects have green roofs for environmental purposes. Most large projects built on expensive land have a roof garden to increase the property’s garden and rest areas. If Thailand could enact a law on green roofing, it would facilitate the recruitment of experts, as well as installation materials and maintenance equipment.
And if those houses around the capital that could afford it were willing to do so, we surely could increase the level of fresh air and reduce heat in the city.
For further information, go to www.bangkokgreencity.bangkok.go.th or www.comeongreen.com.