A smarter way to clad and cover our buildings also offering environmental and community benefits is here – green roofs and walls.
However inimitable the concept of a living garden on a wall or roof of a building may be, this technology is becoming increasingly popular worldwide. It’s not just a fancy option, but a comprehensive, eco-friendly solution. Architects, builders and city planners in India too, are warming up to the idea since it’s feasible for our swarming urban environment and has numerous benefits to boot.
A green roof or living roof is a vegetative layer grown on a rooftop of a building – right from industrial complexes to residential buildings. It’s composed of a waterproofing layer, a root barrier, a drainage system and growing medium for the plants.There are three types of green roofs: intensive roofs, extensive roofs and semi-intensive roofs. A green wall on the other hand is a vertical garden, which can be indoors or outdoors, freestanding or attached to an existing wall and comes in various sizes.
The lightweight, extensive green roof system includes two to six inches of a growing medium and small plants, typically sedums – succulent, hardy plants adapted to extreme climates, which are planted over a root barrier and waterproofing membrane. These require little maintenance and minimum added structural support, which makes them cost-effective. Intensive roofs are like a conventional park or garden with a variety of plants and trees. Being elaborate, they involve a higher initial investment with irrigation systems and regular maintenance. Semi-intensive roofs incorporate the characteristics of both, extensive and intensive.
Green walls are often constructed of modular panels that hold a growing medium: loose, mat or structural. Loose medium systems have their soil packed into a shelf or bag and then are installed onto the wall, mat type systems are either thin coir fibre or felt mats, while structural media are growth medium blocks that incorporate the best features of loose and mat into a block that can be manufactured into various sizes, shapes and thicknesses.
Green roofs are beneficial to us as well as the environment. They provide shade and remove heat from the air through ‘evapotranspiration’ – whereby water is stored by the substrate, later used by the plants and then returned to the atmosphere – thus reducing temperatures of the roof surface and the surrounding air. This in turn can improve indoor comfort and lower heat stress associated with heat waves. Since they absorb heat, green roofs act as insulators for buildings, reducing energy needed to provide cooling and heating.
Green roofs reduce and slow stormwater runoff in the urban environment by absorbing about 90% of rain while their layers filter pollutants from rainfall. By delaying the rush of stormwater into sewers after a rainfall, widespread green roofs can also help prevent flooding and keep the city’s drainage system running for a longer time.
Green roofs also help absorb airborne toxins and carbon dioxide as they photosynthesise, and can provide a welcome habitat for birds as well as decrease the risk of asthma.Moreover, green roofs help create natural habitats by providing a permanent resting haven for various birds, insects, etc.
Green walls too lead to cooler temperatures and are best suited for urban environments since they allow good use of available vertical surfaces. They also provide a breath of fresh air by purifying pollutants and enhancing the inhabitants’ wellbeing.
By reducing temperature fluctuations of the building envelope, green roofs and walls protect the building from cracks, fractures caused by the expansion and contraction of building materials. They reduce energy costs by up to 20% with natural insulation and dampen noise pollution as well. Moreover, urban greening is viable for beautifying the built environment and increasing investment opportunities.
While the average cost of installing a green roof can run two or three times more than a conventional roof, it’s cheaper in the long run, thanks to energy savings. Vegetation also shields the roof from ultraviolet radiation, extending its life.
In India, if we embrace this greener way of living then viewing natural, green spaces instead of all the grey concrete or asphalt around us will be life-changing, won’t it?