Green Roof


A Green roof is a roof of a edifice that is partly or wholly covered with unrecorded flora. The flora is normally planted over a rainproof stuff. The green roof does non mention to the rooftops that are simply coloured green. Green roofs may besides include extra beds of root barriers and irrigation systems. In the instance where workss are grown in pots and so placed in roof tops, these are non considered to be true green roofs. Roof top pools are another signifier of green roof and are used to handle gray H2O ( Little, par. 1 ) . Grey H2O is any H2O that has been used in the place for the intents of rinsing except H2O from lavatories. Water from wash, sinks and showers is all referred to as gray H2O. This H2O normally goes to blow but it may be reused for other intents, particularly irrigation. Grey H2O may hence be run to roof gardens. Green roofs are besides referred to as roof gardens and eco-roofs. Little says that roof gardens serve several intents for a edifice such as absorbing rainwater, supplying insularity for the edifice, making home ground for wildlife, and besides take downing urban temperatures therefore take downing the heat island consequence ( Little, par. 1 ) .

There are two types of green roofs: intensive green roofs and extended green roofs. Intensive green roofs are thicker and can back up a wider assortment of workss. They are heavier and necessitate a batch of care. They are made in such a manner that they are accessible. The other type of green roofs is called extended green roofs. These types of green roofs are covered by lighter flora and are easier to keep than the intensive green roofs. They are chiefly developed for aesthetic intents, but besides have assorted advantages to the environment.

Green roofs can besides be used to mention to the types of roofs that can utilize some signifier of green engineering such as cool roof with photovoltaic faculties. Photovoltaic faculties are interconnected assembly of solar cells. The chief intent of the solar panel is to change over the solar energy into electricity.

Environmental advantages of green roofs

Population growing in the universe today is go oning at a really rapid rate. Many metropoliss in the universe are quickly going extremely urbanized with the building of edifices and constructions in close contact with each other. Increased building of concrete edifices has led to the loss of green screen thereby making a batch of environmental issues such as urban heat island consequence. This has generated a significant addition in air temperature in urban countries. The energy ingestion has increased as an result of the heat island consequence. Plants and floras play a really critical function in pin downing soil and dust atoms in the air. Plants besides utilize C dioxide in the procedure of photosynthesis and generate O and glucose molecules during the twenty-four hours. This helps in decrease of C dioxide in the air every bit good as increasing the sum of O in the air. In the procedure of urban development, trees are cut down at a really high rate. This leads to lowering of the air quality as degrees of C dioxide will increase and oxygen degrees lessening. Harmonizing to Dowdey ( para 3 ) , places where there are no rooftop gardens, rainwater flows really fast from the edifices ‘ roofs into the cloaca and in instances where the cloaca can non get by with the sum of H2O fluxing from the roof tops, inundations occur.

The chief cause of island heat consequence in the urban countries is the soaking up and keeping of solar heat in edifices and other concrete constructions ensuing in the air temperature in such countries going heater than in the rural countries. Increase in temperature means that the air conditioning burden of these edifices will hold to be increased. This means that more energy will be needed by the conditioners which will in return release more warm fumes air into the out-of-door therefore worsening the urban heat island consequence. Roof gardens have been shown to take down the surface temperature and the air temperature greatly. Small provinces that the chief ground why green roofs lower these temperatures is because, they cover the heat absorbing surfaces of the roof tops every bit good as the evapotranspiration chilling effects of the workss.

Bettering Air quality

Roof flora improves the air quality by moving as a filter to pin down air borne dust atoms. A roof that has got a high temperature tends to make a thermic bill of exchange pulling dust atoms from the streets. The green roofs have been found to chair the thermic bill of exchange therefore cut downing the temperature difference between the roof tops and the streets. Green roofs besides help to cut down the formation of smog. Smog is really sensitive to high temperatures and the fact is the higher the temperature, the higher the concentration of smog. Harmonizing to Dowdey, workss through the procedure of photosynthesis absorb C dioxide and release O into the atmosphere therefore bettering the air quality ( Dowdey, par. 4 ) .

Bettering H2O quality

The green roof helps to filtrate out most of the heavy metals and foods present in rainwater. This is really good in urban countries where precipitation is collected for domestic use.

Decrease of storm H2O

Roof gardens retain most of rainwater on the roof through the assorted beds and significantly cut down the extremum discharge flow rate into the storm H2O drainage system. This helps to cut down the hazard of brassy implosion therapy.

Energy preservation

When surfaces absorb a batch of solar heat, urban heat island is the ensuing consequence. This in bend causes a significant addition in the atmospheric temperature within the urban centres. This will in bend lead to a batch of energy ingestion for chilling tonss. Roof gardens aid to absorb a batch of solar heat that would otherwise increase the atmospheric temperature. Cooling tonss will therefore non be required to such a great extent and hence decrease in energy ingestion will be the good result. Green roofs besides aid in cut downing heat loss and energy ingestion in winter conditions ( Kuhn, p 5 ) .

The green infinite

Green infinites are really good to people populating and working in the urban centres. These infinites help in back uping biodiversity, softening the edifice ‘s environment, and helping peoples ‘ mental and physical wellness. Green roofs better the value of the green infinite by supplying accessible green infinite. Green roofs are really appealing to those who look at them. Some green roofs can be designed for people to bask ( Dowdey, par. 7 ) .

Cost benefit

If 50 % of the roofs in Tokyo were covered with roof gardens, a survey showed that air temperature could be reduced from between 0.11°c to 0.84°c. Translation of these figures into existent dollar value estimated that about $ 1.6 million per twenty-four hours in electricity measure could be achieved as energy nest eggs. Kuhn ( p 6 ) provinces that approximately 15 % of one-year energy economy can be achieved with roof gardens. Cooling tonss can be drastically reduced up to 80 % ensuing in retrenchment of air conditioning systems which would greatly better nest eggs in capital investings. A decrease of extremum roof thermic transportation value of up to 80 % make the roof tops a feasible replacement for thermic insularity.

Extension of roof life

Harmonizing to Dowdey, roof gardens protect the H2O proofing membrane every bit good as the roof top surfaces from the harmful effects of the extremist violet beams. Most of the H2O which would usually make the roofing stuff doing moistness and rust is either taken by the workss or retained by the H2O cogent evidence membrane ( para 8 ) . Protection of the H2O proofing membrane and the roofing stuff extends their life to about four times their mean life. The H2O cogent evidence stuff and the roofing stuff itself will non be tampered with in the procedure of regular replacing. This greatly improves the life anticipation of the roofing stuffs. Green roofs besides play a really of import function in protecting roofs from human traffic, heavy dust and dust atoms. This means that the roofs are safe from being tampered with by people ( Dowdey, par. 9 ) .


Proper planning for the installing of a green roof greatly reduces the disadvantages that may be accompanied with it. However, some types of green roofs do hold more demanding structural criterions than others. Some bing edifices can non be retrofitted with certain sorts of green roofs because of the weight burden of the substrates and the flora which exceed the permitted inactive burden, besides referred to as the external force applied to a fixed place for a specific period of clip. Depending on the type of the green roof, the cost of care could be high. Some types of green roofs particularly the intensive green roof require a really strong H2O proofing stuff to forestall H2O and roots from perforating the H2O cogent evidence membrane. Installation of equal H2O proofing stuffs and root barriers requires a considerable sum of money. The flora on the gardens requires particular fertilisers which can sometimes be really dearly-won ( Kuhn, p 7 ) .


Green roof are hence really good to human non merely in footings of environmental protection but besides in footings of economic system. Their advantages are really many as compared to their disadvantages. The functions played by green gardens have a really great impact in our lives. Alteration of the environment through take downing the island heat, pull offing storm H2O, cut downing air and H2O pollution and making a wildlife home ground are some of the green garden ‘s environmental benefits. Green roofs have besides been shown to increase the roof life every bit good as cut down energy costs. Bearing in head the benefits of the roof gardens, the cost factor may be looked at the least in order for roof gardens to be widely adopted.


  • Dowdey, Sarah. What is a Green Roof? , 2009. Retrieved on November 27, 2009 from hypertext transfer protocol: //
  • Kuhn, Monica. Roof Gardening, 1996. Retrieved on November 27, 2009 from hypertext transfer protocol: //
  • Small, John. Green roof preparation, 2009. Retrieved on November 27, 2009 from hypertext transfer protocol: //