A green roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. Green roofs are unique because they provide insulation, absorb rainwater, moderate temperatures, and improve air quality. All these attributes contribute toward sustainability.
There are mainly three types of green roofs: extensive, intensive, and semi-intensive green roofs. Extensive green roofs are smaller in thickness but span a wider area and have a limited diversity in terms of plant species and limited watering requirements. Intensive green roofs in contrast are characterized by a deeper growth medium, wider diversity and more demanding watering requirements. semi-intensive is an in-between that characterizes the previous two types.
Installation considerations for green roofs; Before installing a green roof, one should consider the following factors.
Compatibility; One should consider whether the vegetation type is compatible with the roof cover or even suitable for that area. For instance, some vegetation will be sensitive to high temperatures whereas others will strive in those same conditions.
Cost; One should consider their budget before picking a green roof type. Cost is considered both in terms of installation and maintenance costs. Intensive green roofs are more expensive to install and maintain compared to extensive green roofs. Thus ones choices should be aligned with their financial muscle.
Objectives; One should also consider their objectives before making a choice. Objectives range from energy savings, to aesthetic appeal, water conservation among others. Different green roof types and different vegetation have different properties thus meet different objectives.
Before choosing a green roof as a roofing option, one must first be familiar with the various pros and cons of green buildings.
Pros;
Green buildings improve air quality by absorbing carbondioxide and any other air pollutants. It is no secret that living spaces enhanced with plant life, mostly as plants in pots and vases often have a cool refreshing ambience. This improves the habitability of a living space.
Green roofs have an insulating property. Because plants absorb extra sunshine from the roof, the roof as well as the interior is protected from intense direct sunshine thus insulated and kept cool. They insulating properties also works to minimize heat loss in cold days. All this optimizes the temperature and thus the living conditions of a space.
Cutting energy costs; Due to the insulating properties of green roofs, they cut the total energy expenditures of a building. Costs on heating or cooling are all cut down thus proving to be a cost efficient roofing option.
Sustainability; By cutting down energy requirements, green roofs reduce the reliance on energy produced from fossil fuels thus contributing to environmental conservation and sustainability in the long run.
Membrane longetivity; Green roofs are designed in a way that vegetation covers the primary roof cover. This shields the roof cover from extreme weather elements in form of sunshine and rain. This protects the roof cover from U.V rays, thermal stress, frost action, rust among others. This contributes to the longetivity of the primary roof cover.
Acoustic insulation; In addition to insulating properties, green roofs also portray properties of acoustic insulation. That is, insulation from noise. Such an attribute can come in handy in noisy environments for example an airfield.
Aesthetic benefits; Green roofs give a building a touch of elegance especially when the vegetation is nicely trimmed and well designed. This adds value to a property. For a commercial property, aesthetic appeal might mean the difference between low or high rents.
Drainage; Green roofs have better drainage properties. The vegetation partially retains and better channels the runoff and distributes it to the piping system at lesser safer pressures. The vegetation mass also filters the run off making recycled rain water clean.
cons;
High initial cost; Green roofs attract a high installation cost in terms of surface preparation and any other forms of modification of the original roof. This might involve water proofing the roof, setting up irrigation and drainage systems among others. All such costs when summed up lay a hefty financial burden on the barer.
High maintenance and running costs; The vegetation on green buildings ought to be watered and treated regularly. This poses the need for irrigation systems that comes at a running cost in form of system maintenance. The vegetation also requires maintenance in form of weeding and pest control, all which cost money, in form of money, labour or both.
In conclusion, sustainability in roofing is about looking at the big picture and making decisions that will have long-term benefits. A green roof can play an important role in mitigating climate change and should be considered for any building that wants to be seen as sustainable. It also cuts down on energy costs, reduce storm water runoff, and increase sthe value of a property and make it more attractive to buyers.
