What Is a Green Roof

Contents

Many of you may be well aware, but some must be thinking, “What are green roofs?” Let us shed some light on this.

A green roof, also known as a living roof, is like an embedded system in which small plants and shrubs are grown on the roofs of buildings. Green roofs can be created directly on your rooftop or you can buy and embed planting trays. In these planting trays, the plants are grown in advance and you just need to install them onto your rooftop.

Though being in existence for centuries, green roofs have gained importance in the recent years with the advancement of membrane waterproofing technology. This technology combined with lightweight green roofs, and from then they gained more value.

Types of green roofs

There are mainly two types of green roofs, which are differentiated by the depth of soil, types of plants and the cost of installing. These types are extensive and intensive.

  • Extensive green roofs
  • Extensive roofs are inexpensive to install but you need to limit your choice of plants. In these roofs, a thin layer of growing material is used, which is a mixture of sand, gravel, organic matter, peat, crushed bricks and a major portion of soil. This mixture is installed up to the depth of 5-15 cm; its saturated weight varies from 73-169 kg/m2. The plants grown on these roofs must be low and hardy, and indigenous or those that are best for dry land. This is because the shallowness of the soil provides the roof with a desert-like climate.  Extensive roofs require minimum maintenance. The plants of these roofs are watered only until the completion of their establishment, and after that, they need watering after one year of the plantation. Also, fertilization is done while establishing the roof.

    No special maintenance is required after that. You just need to inspect the installed membranes and weed the species twice a year. These types of roofs look more natural.

  • Intensive green roofs
  • The growing medium of intensive roofs is mainly comprised of soil, which is installed up to a depth of 20-60 cm. The saturated weight ranges between 290-968 kg/m2. The plants in these roofs can be selected from a large variety, which can also include shrubs and trees. Thus, a more complex eco-system is developed with the plantation of such plants. These roofs demand regular maintenance, which includes watering and fertilization. Also, it is recommended to get them installed with the help of an experienced installer. Due to the thickness of the soil, the membranes last longer as compared with extensive roofs.

WHAT IS A GREEN ROOF MADE OF?

A green roof is a well-planned structure that needs to be installed by experienced professionals. It is made of multiple layers that serve the purpose of water retention, insulation, water filtration and more. Above these layers, soil is distributed equally up to the length that ranges from 5-60 cm. Then plants are grown in this soil, which provide many benefits.

HOW GREEN ROOFS BECAME PROMINENT

Green roofs have been in existence for centuries, but they are not very prominent. With the passage of time and the advent of technology, they have gained importance. The main factors that lead to this change are increasing environmental problems and increasing population. You may be thinking how these factors affect the concept of green roofs. Let us give some explanation. With the regular increase in population, the demands for basic needs are also increasing, and housing is among these needs. To fulfil the residential needs of the population, green land is regularly consumed for constructing residential buildings. Industrial construction is also booming to fulfil the needs of the public.

All these situations lead to environmental problems like deforestation, emission of greenhouse gases, ozone layer depletion and many more. Fortunately, technology has brought about the idea of green roofs.

HOW GREEN ROOFS ARE BENEFICIAL

Many of you may still be thinking, “What is the purpose of a green roof?” By reading these benefits, you will definitely get to know them. Green roofs are not only beneficial for having positive effects on the environment, but they are also economical. In this era of urbanisation, Green roofs are the best way to increase and maintain traditional vegetation without having any negative effects on urban infrastructure. Also, in today’s time, when inflation is gradually increasing, it is normal for every man to think about saving his money. Green roofs enable you to reduce your cooling and heating expenses in different seasons. In the winter, they protect you from extreme cold and in the summer from the heat. What can be better than that?

Here are some benefits of green roofs:

  • Green roofs are the best source of fresh air in polluted environments, especially in urban areas.
  • The lifespan of the roof increases by three-folds with the installation of a green roof.
  • Along with curbing air pollution, green roofs also limit the amount of noise reaching the inner part of buildings.
  • Living gardens also reduce the impact of carbon monoxide that is emitted by various fuel-burning devices.
  • Green roofs provide a natural habitat to many wild species that feed on the roof’s small plants and grasses.
  • Storm water run-off is restricted by these green gardens. This prevents the buildings from getting damaged.
  • You must be aware of the detrimental effects of acid rain. By installing a green roof on your rooftop, you can neutralize those effects.

GREEN ROOF SECTION DETAILS

A particular green roof section is a layer that is installed anywhere on the roof. Here we are mentioning these sections in the series starting from the bottom:

  • Waterproofing system
  • Insulation
  • Protective layer
  • Drain layer
  • Containment
  • Filter layer
  • Planting medium
  • Vegetation

The structure of the green roof cross section contains a waterproof membrane next to the roof deck. Then, another layer of membrane can be installed for leak detection, but it is optional. Above that, an insulation layer is installed to eliminate the need for special insulation in extreme weather conditions. Then a drain layer is installed above this insulation, which directs the water flowing on the roof to the drainage system of the house. That’s all you have to do for waterproofing your roof decking. Now, the next layer is of soil, also known as the growing medium. On the top, vegetation is grown and the variety of plants grown depends on the type of green roof.

WHAT DO GREEN ROOFS DO FOR THE ENVIRONMENT?

Green roofs are very beneficial for the environment. Some of these advantages are:

  • Improved water quality
  • As the rain water flows through a green roof, the installed filters filter the water for various harmful constituents, which include phosphorus, nitrogen and many other toxins. This filtered water then flows through the drainage system and enters the waterways and streams. Thus, green roofs have a crucial role in improving the quality of water.

  • Improved air quality
  • The vegetation foliage grown on the roof in the form of green roofs filters the various airborne particles. These particles include carbon dioxide, sulphur dioxide and many others. In urban areas where people can’t see the blue sky due to increased pollution, green roofs serve the purpose of providing clean and fresh air to people.

  • Stimulate biodiversity
  • The increased construction disrupts microhabitats, which can be re-established with the installation of green roofs. Green roofs help in restoring the ecological cycle that in turn provides the microhabitat in highly populated areas. The biodiversity can be stimulated by selecting the variety of plants and substrate in proper amounts.

  • Reduction in storm water runoff
  • Due to the disrupted ecological cycle, floods rates are increasing. Thus, buildings should be able to endure heavy downpour.  In such cases, green roofs are becoming more prominent for the retention of water. Green roofs are able to retain 70-100% of storm water in the summer and 40-50% in winter. This results in reduced soil erosion and sedimentation.

  • Reduced “Urban Heat Island” Effect
  • During the summer, urban areas become hotter than the countryside. This difference in the temperature is approximately 10 degree (F). And this observable fact is known as the “Urban Heat Effect.” Green roofs are applicable in reducing this effect as green plants make the air cool by emitting moisture.

WHAT ARE GREEN ROOFS USED FOR?

The uses of green roofs depend on the individual. As mentioned above, green roofs are mainly used for storm water management, increasing the lifespan of a roof, lowering energy costs, getting clean air and water and many other purposes. Apart from these multiple uses, people also construct them for recreational purposes. Well-planned and creatively designed green roofs also add to the beauty of buildings along with providing so many benefits.