Focus on green roofs, a sustainable solution for solar heat gain issues

Credit: Siam Green Sky - SCG

Southeast Asian countries as Thaïland have a tropical climate influenced by monsoon winds. Because of that, these countries suffer regularly from high temperatures and heavy rainy seasons. This variations cause periods of drought and extreme heat during which energy consumption explodes and periods of flooding that drains pollution into the ground and potentially damage urban installations.

Green roofs are an excellent solution to prevent tropical climate challenges. A vegetated roof protects the indoor spaces against heat transfer and limits the urban heat island effect around the site. The Environmental Protection Agency (EPA) describes this phenomenon as “built up areas that are hotter than nearby rural areas”. By absorbing heat, green roofs reduce electricity load from cooling devices, hence energy costs, while decreasing the production of associated greenhouse gas emissions. To do so, green roofs rely on evapotranspiration which keeps buildings cool by using heat in the air to evaporate the water in the rooftop plants. They remove air pollutants and greenhouse gas emissions through carbon sequestration and storage. Additionally, green roofs offer new habitats for wildlife chased away from urban life.

These underutilized spaces have multiple benefits that enhance communities quality of life such as:

Limiting urban heat island effect. Vegetation on green roofs decrease roof temperatures and provide moisture through evapotranspiration. This contributes to reduce the overall urban heat island effect in the area and decrease the energy demand of surrounding buildings.
Improving stormwater management. Green roofs absorb rainwater which reduces peak runoff rates on the site and streets.
Increasing energy efficiency. Roof surfaces are often one of the predominant solar heat transfer area. By insulating roof surfaces, green roofs cut down peak energy demand and reduce air-conditioning costs.
Reducing smog and improving air quality. Plants from the green roofs absorb carbon dioxide (CO2) to reject oxygen (O2) through photosynthesis. Furthermore, their leaves trap dust particles and filter fine particulate matter from the air which helps to reduce surrounding air pollution levels.

Depending on project requirements and constraints, a green roof can be referenced in 3 categories:

Extensive roof, lightweight and easy to install, it is suitable for large areas. Professionals recommend it for inaccessible roofs and flat or sloping roofs.
Semi-intensive roof, used within highly visible areas to improve aesthetic design It requires a moderate maintenance and occasional irrigation.
Intensive roof needs stronger structures and more care as it needs regular irrigation and maintenance. It is comparable to a on the ground natural garden as it can be used for recreation, sport and farming.

Credit: Concepto Verdevertical

After a theoretical approach, here comes some examples of green roofs in Thaïland.

Siam Shopping Center:

Type: Intensive green roof

“Chulalongkorn University has opened an urban agricultural learning center called Siam Green Sky on the top floor of the Siam Square One shopping center. The project covers an area of 2,000 sq.m on the 7th floor and is considered to be the largest rooftop garden in Bangkok.” (Source - Thai Travel news & events)

Pandora:

Type: Intensive green roof

“Pandora A/S, the international Danish jewelry manufacturer and retailer, has partnered with Thai Garden Design to design and install their complete Green Roof Landscape, across the top of their new production facilities in Bangkok.” (Source - Thai Garden Design)