Advantages And Disadvantages Of Green Roofs

Gardens which are constructed on the roofs and balconies for rising vegetation starting from flowers to greens are called terrace backyard. The development of developing a terrace garden just isn’t something new and its origination dates again to 1000’s of years ago during the civilization of Mesopotamia.

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“Ziggurats of Mesopotamia” which had been constructed between four,000 – 600 BC had no inside rooms, trees, and blooms on every porch of the gigantic ziggurats would give a cool, obscure spot for the guest to relaxation from the bursting Babylonian sun.

The Hanging Gardens of Babylon are one of the Seven Wonders of the Ancient World and perhaps essentially the most acclaimed of rooftop gardens.. It was constructed throughout eighth to sixth century BC. Notwithstanding, the newest patterns in rooftop nurseries are both environmental and useful. Nowadays the potential for the rooftop nursery has been changed into the green rooftop As a result of the quick expansion of human civilization, all of the forest, fields, and grasslands are being substituted by concrete and metal resulting in excessive pressure on the land.

(Citation, n.d.)

With the growing stress on the land, the idea of terrace gardens has been gaining plenty of recognition.

At the present time, the most vital phenomenon associated to high temperatures in most places is the “Urban Heat Islands (UHIs). An city space that is considerably hotter than its surrounding rural areas due to human actions is called city warmth island. The impact of UHI can be mainly felt in summer time and winter.

The four main reasons for the phenomenon of city warmth island are:

  • The change in thermal properties of the earth surface
  • Buildings being an impediment to the wind flow
  • Change in moisture situation because of urbanization
  • All the warmth and pollutants emitted into the setting due to urbanization.

Lately, folks have become more involved about the effect of city heat islands and are looking for methods to attenuate the results. Many researchers have been accomplished attempting to develop strategies and construction materials that may take up much less heat. It is unrealistic to demolish all the existing buildings so as to rebuild them using the brand new approach and supplies. Terrace garden in its personal small way helps in reducing the urban hear effect. (Alhashimi, Aljawi, Gashgari, & Alamoudi, 2018)

Apart from terrace gardens resisting the city island impact, terrace gardens are also advantageous in reducing the rain runoff.

Types of Green Roofs

There are three major types of green roofs according to FLL pointers: intensive, and intensive primarily based on the particular green roof meeting and cargo characteristics.

Extensive Green Roof

It is the most affordable of the three types of systems. It is designed as an ecological roof garden as an alternative of a luxury house. The depth of the substrate vary from zero.8 to six inches. Only low rising herbaceous crops, similar to mosses and grasses are grown in this type of roof backyard. (No Title, 2010)


  • Lightweight, no reinforcement is required on the roof
  • Suitable for large areas
  • Less upkeep and longer life
  • Looks natural


  • Energy efficiency is less
  • Choice of the plant is limited


This type of roof system basically imitates conventional gardens at floor stage. The media is usually more than 8 inches. This type of roof garden can develop timber, herbaceous plants, and lawns.


  • Wide range of plants
  • Good insulation properties
  • Less maintenance and longer life
  • More vitality efficient.


  • Load on the roof is more
  • High investment and upkeep cost.

Considerations for Establishing Roof Garden

Before establishing a rooftop backyard, we ought to always take into consideration after perspectives:

The greatest time to develop a rooftop backyard is the point at which the rooftop is recently built or being fixed. When working with a current rooftop, we ought to always think about the current leakages, harm, failure to oppose roots and standing water and so forth.

  • Structural capability of the rooftop:

Preceding structuring and constructing a rooftop garden, we must always determine whether or not the rooftop can stand up to the additional weight of soil and vegetation. The structural limit of the rooftop largely decides the kind of rooftop backyard that may be assembled.

Access to the rooftop is a major consideration. Normal access incorporates stairs or emergency exits. Be that as it could, there must to be enough area for transport materials for improvement and upkeep.

Thought of weight is the core of preparing for a rooftop garden. Weight of the garden should be controlled by approved planner or basic designer. It must be assured that the burden of the garden doesn’t surpass the fundamental restrict of the rooftop

Before beginning a rooftop garden, all essential price examination should be carried out. Usually, green rooftop prices half greater than odd rooftops. Also, an in depth backyard is less exorbitant than an escalated garden. (Consideration, 2009)

  • Plan of a rooftop backyard:

The plan of a rooftop garden could differ with the structural capacity of the construction, proprietor’s near a home decision, the motivation behind cultivating, surrounding surroundings, and so forth.

Rooftop nursery crops to a fantastic extent depend on downpour water for the water systems. Be that as it could, during a certain time of yr, precipitation could be lacking to satisfy the water necessities. So, harvesting of downpour water must be potential. In addition, trickle water system framework, hose-pipe handbook watering, and so forth must be masterminded to boost precipitation.

Components of Green Roofs

Green roof assemblies are common of two systems of two techniques i.e. roof base and above membrane vegetated roof system. The roof base is made up of a waterproofing membrane, inflexible insulation, safety, and structural system. The vegetated roof system consists of eight functional layers: vegetation, engineered fill, insulation, filter material, drainage layer, root barrier, waterproofing membrane and structural support. The requirements of these layers depend upon conditions, some layers may not be needed in some conditions whereas some conditions require extra layers. ( Engineers & Angeles, 2008)

Anatomy Of A Typical Green Roof Assembly

  •  Vegetation: The panorama of the place performs a significant role in the selection of green roof vegetation. A lifeless load of ground vegetables ranges from 2 to 4 psf. Appendix A shows the additional design useless loads for different green roof types and crops.
  • Growing Media/ engineered soil layer: The depth of the rising media is decided by the kind of plant choice.
  • Insulation layer: this layer is both laid beneath or above the waterproofing membrane. When the insulation layer is laid below, the system is considered as an inverted roof membrane meeting (IRMA). This system takes advantage of the insulation layer to guard the waterproofing membrane from puncture and UV degradation. The compressive energy of the inflexible insulation board have to be adequate enough to take the load. Despite the fact that a green roof can function an insulating layer, it has been recognized that climates having extended durations of winter will nonetheless require an insulation layer. (Scholar & Engineering, 2019)
  • Filter/Separation fabric a none clogging, synthetic filter fabric (nonbiodegradable) is put in to maintain the drainage and water storage capabilities of the drainage layer. The filter material ought to be manufactured from a construction that resists clogging from nice soil particles. Generally, this filter material is simply about 1/8 inch thick.
  • Water storing drainage layer: this layer principally has two competing traits: 1) Drainage of water from the plant root zone 2) storage of water to supply plants with moisture in periods of dryness. The three main kinds of drainage layers are 1) Drainage plates 2) Granular media and drainage mats.

Drainage plates are the waffles inflexible thermoplastics which might be simple to put in and varied sizes are available. The drainage plate system is usually about 1 inc to 2-.5 inches tall. Granular media system consists of a base layer of light-weight, inorganic, granular media. This granular media is composed of porous lightweight combination. The granular media system is about 2 to six inches. Drainage mats are the thinnest, lightest and quickest to put in. This system consists of a multi-fabric mat that combines sol separation, drainage, and protection capabilities. The only drawback is its restricted water storage and drainage capability. Its thickness ranges from 3 to 8 inches. (Shafique, Kim, & Kyung-ho, 2018)

Drainage Layer System (Resource Conservation Technology 2006)

  • Protection cloth: This layer is t usually placed above the waterproofing and root barrier membrane. The main perform of this membrane is to prevent damage throughout building and roof upkeep actions. Protective fabrics with water storage and capillary capabilities may also be designed.
  • Root safety barrier: some waterproofing membrane likes bituminous and asphalts usually are not proof against root penetration or degradation. Root barriers are often made from PVC and typically contain release agents. The thickness of this layer vary from zero.03 to 0.04 inches.
  • Waterproof layer: it is a vital a part of the system if we want a long-lasting and maintenance-free lifetime of the green roof.

Beneficial Impact of the Roof

  • Reducing the city warmth island effect

Urban heat island is the overheating of the city areas in comparison with the encircling rural areas that are because of the growing human actions. Introduction of greenery via green rooftops in the city zones can reduce impenetrable surfaces and mellow streetscapes. Plants use warmth vitality for evapo-transpiration to perform a cooling impact. By diminishing the heat increase through the rooftop encompassing temperature is brought driving down to much less vitality utilization .Internal construction temperature by zero.5?C. It also decreases the power consumption for air conditioning.(Bahru, Rashid, Hamdan, & Ahmed, 2009)

Green rooftops assist to shield material films from extraordinary temperature vacillations, the unfavorable impact of brilliant radiation.

Green rooftops can assume a major job in giving leisure areas in urban locales where there is little ground-level green territories. As these spaces are noticeable from quite a few vantage focuses, it adds to the visible character of the urban texture.

Energy Proficiency And Temperature Control

The more noteworthy protection offered by the porch nursery can diminish the measure of vitality required in a construction.

Rooftop surfaces supply the open door for developing nourishment, especially in high thickness city regions where nursery space could be constrained. – nourishment creating plants can substitute for elaborate plants in customary rooftop gardens.

Green rooftops channel out fine, the airborne particulate concern as the air ignores the plants. Airborne particulates will, normally, get caught in the surface territories of the greenery.

  • Sound protection/controls commotion contamination.

Hard surfaces of urban regions replicate sound and can’t ingest it. Green rooftops due to the vegetation retain sound waves(Mahdeloei, Farahani, & Shakori, 2012)

Negative Impacts of the Roof Garden

Roof Garden Weight and Structure

Most buildings and houses constructed before are constructed with brick and concrete or with a cement body. Engineers and designers did not consider foreseeing the set up of a green roof at that time. A discussion with the original constructors on roof loading is important when arranging the institution of a housetop backyard. There are two forms of roof loading:useless load and stay load. Dead load refers again to the weight of the roof construction itself and any permanent constructions on that roof. To accommodate weights beyond the lifeless load (from snow or rainwater), buildings are usually designed with a “live loading capacity”. This is supposed to bear the burden of snow within the winter, but rooftop gardeners can use it through the summer season, bear in mind the whole weight of the roof garden and the retained water. Unfortunately, most formerly constructed roofs are not designed to assist an intensive backyard with an enormous substrate layer and large crops. Only an intensive garden, with a skinny layer of soil, mosses, herbs, sedum or different succulent vegetation, appears appropriate here. On the opposite, a modern building’s roof ought to at all times be planned to help the load of a roof backyard. (Sharma et al., n.d.)

Soil and planting pots are each substantial – regardless of whether you make a dust planting mattress in your rooftop nursery or use pots, you are basically together with to the burden put the rooftop construction. Yard sections and furnishings further embody the burden of the rooftop. Most constructing rooftops would require applicable fortification before a rooftop nursery could be developed securely. High rooftop nurseries might have points with excessive breezes harming crops and youthful seedlings.

Water Supply

Typical gardens on the floor level, built-in recently created pieces of the town, might expertise some issue getting to the water. Tops of present buildings, in differentiate, are quite often near conceivable inventory of city water or faucet water from the top flooring. However, collecting precipitation water for plant creation is more becoming than using urban water.

On the opposite, in additional established items of the cities, irrigation frameworks for watering crops in a rooftop nursery could be absent, which makes its upkeep very difficult. Therefore, one ought to right off the bat search for a good answer for this significant issue. Here, the TC-strategy to stock water within the root zone might help in a huge method.

Discovering conceivable outcomes to reap and retailer downpour water should persistently be a necessity for anybody increase an city nursery. It is staggering how brisk the filth of a rooftop nursery is drying out and plants will shrivel all the time if commonplace watering, early toward the beginning of the day or late within the night, is overlooked. During mid-year, watering should by no means be accomplished within the day.

As low yearly precipitation is influencing straightforwardly plant improvement in a rooftop backyard, it can be essential to approach the metropolitan water supply, e.g. for the dribble water system.

Gathering precipitation water for the ulterior water system can represent a problem, as there is generally no appropriate area to retailer an infinite vessel. To give passable weight within the dribble water system framework to be imagined, a gravity-bolstered hose will require a inventory tank launched lots greater than the hose shops. Another concern would siphon faucet water into this inventory tank in the occasion that it was arranged on a similar rooftop. The heaviness of the tank would must be appropriated equitably over a big zone to arrive on the live-load farthest level of the rooftop. These variables could make the water system framework and water accumulation impractical. The issue waterway so comes on the opposite end of the spectrum, i.e. there could nearly be an excessive quantity of water.

Therefore, one must ideally search for a satisfactory framework to improve the water maintenance restrict of the substrate in order to inventory constantly enough volumes of water to take care of a strategic distance from dry season pressure. The conceivable extra of water during tempests must be successfully depleted. The quantity of water held within the substrate must be promptly accessible to the plant roots to abstain from the shrinking of the vegetation over a extra drawn out dry interval.

Perhaps the best method to stock water and manure within the substrate of a rooftop nursery known as theTerraCottem-or TC-method which was created by the college of Ghent(Belgium)in1983-1992. It has been utilized since 1995 in China (Greenhouse enterprise in Lanzhou, Gansu Province) and it has demonstrated its viability in varied Chinese regions from that point forward. The TC soil conditioner is a mix in excess of 20 granular substances, all helping plant development in a synergistic method. These substances may be separated into 6 gatherings:

  1. Water retentive polymers
  2. Soluble mineral manures
  3. Slow discharge mineral composts
  4. Synthetic pure composts
  5. Carrier material (volcanic shake or “magma”)
  6. Growth activators for roots

Small amounts of the TC, mixed into the foundation zone, have a quantity of constructive outcomes:

  1. Improvement of plant and root development
  2. More blossoms
  3. Reduction of the quantity and recurrence of the essential water system
  4. More opposition of vegetation to withstand instances of dry season pressure
  5. Activation of the microbiological action
  6. Reduce repairs costs

Layer Installation

In the event that a rooftop backyard has soil beds, a defensive layer ought to be introduced between the dirt and the structure’s housetop. Introducing this layer is an skilled activity and can be expensive. Rooftop backyard movies can progress towards changing into debased after a while or cracked by screws, nails or the utilization of digging tools. A cracked layer can breakwater and soil into the construction. Redesigning or supplanting the film could require total expulsion of the rooftop backyard, which interferes with you to the beginning point relating to nursery arranging and plant improvement

Protection and Safety

There is a excessive chance that your structure having a rooftop garden, odds are that insurance coverage businesses will cost a higher premium than they would to cover a similar structure with no rooftop backyard. More noteworthy protection expenses speak to a different method by which a rooftop nursery is frequently extra expensive than a normal nursery. Rooftop nurseries could be riskier than regular nurseries, because of the hazard of falling. On the off chance that you’ve got got – or welcome over – kids to your rooftop backyard, guarantee the perimeters of the nursery are blockaded so nobody can tumble from the rooftop.