A roof garden is a garden on the roof of a building

A roof garden is a garden on the roof of a building. Besides the decorative benefit, roof plantings may provide food, temperature control, hydrological benefits, architectural enhancement, habitats or corridors for wildlife, recreational opportunities, and in large scale it may even have ecological benefits.
“Roof garden” is used particularly for sites where less space is dedicated to the vegetation and growing substrate and more to hard foundation such as decking.
In the book “Roof Gardens: History, Design, and Construction”, Theodore Osmundson defines a rooftop garden as, “A roof garden is any planted open space, intended to provide human enjoyment or environmental enhancement that is separated from the earth by a building or other structure. It may be below, level with, or above the ground.” For this study of rooftop gardens it is assumed that “rooftop garden” refers to above ground structures only.
Rooftop gardens are gardens meant for people to directly enjoy and interact with. They are often modeled after the traditional on-the-ground garden but on a roof.
I emphasize the use of rooftop gardens for food production, but they can be used for any type of gardening.
Biodiverse roofs Figure 13 are designed to create a lodging for a specific requirement for flora and / or fauna. This may be to replicate or enhance the pre-development surroundings.
For instance particular plant species may be required to attract a specific type of bird, butterfly or insect. Biodiverse would include brown roofs, which in their most extreme scenario are left without vegetation with the growing medium selected to allow, over time, the indigenous plant species to colonize the area.

Green roofs are another name for vegetated rooftop space. The term “Green Roof” refers to a waterproofing layer with a covering of plants. The plants are supported by a number of layers on top of the waterproofed surface that could include all or some of the following:
1. Protection layers. It is vital that the waterproofing layer is protected from harm.
2. Drainage layer. Ensuring that water can move laterally across the roof is important for both the plant layer and the entirety of the waterproofing. The drainage layer may also have some maintenance capacity to improve plant growth.
3. Filter layer, Ensures water can reach the drainage layer whilst protecting the drainage layer from blockage.
4. Substrate layer, Growing medium formulated to requirements of site and plant layer.
5. Plant layer.
The system for Green roof with layer of lightweight cultivation is commonly distinguished between “intensive”, “semi-intensive” and “extensive” according to the amount and quality of maintenance required by vegetation, to the total budget of consumed energy and the accessibility to the coverage.

Intensive Green Roof:
Intensive green roof is the type of green roof that contains different types of vegetation starting from grasses, shrubs to small trees. It’s often roof garden and it may also include walkways, benches, tables, and fountain on the roof. The intensive green roof has a depth greater than 150mm. Intensive green roofs are generally heavier, they are willingly accessed by people.
Intensive green roofs need more irrigation and maintenance than extensive roofs, and are highly engineered landscapes, often built directly on structures with considerable weight load capacity, such as car parks. “Roof gardens” or “podium roofs” are terms also used to describe these types of green roofs. Intensive green roofs offer a great potential for design and biodiversity.
Theres some case studies of Intesive green roof:

Peggy Notebeart Museum
The Peggy Notebeart Museum features a series of green roofs ranging from a sloped extensive green roof to an intensive green roof. The intensive portion, features a 7-25 cm drainage layer and a 7 to 20 cm growing media layer, exhibits diverse examples of habitats. The incredible set up of this green roof supports flora ranging from wetland plants to small trees.
Figure 15

Chicago City Hall
The Chicago City Hall green roof profile is 10 cm in depth on a Geofoam landscape. This roof amply supports over 150 plant species, including woody shrubs, vines and trees.
Landscape architects selected the plants for their hardiness, native origins and their hardiness to the extreme temperatures and wind of the city. Jörg Breuning consulted this project in all regards and developed Green Roof solution tailored for this unique location – and the first green roof in the USA according modern green roof technology. Figure 17

2. Semi-Intensive Green Roofs:
Small herbaceous plants, ground covers, grasses and small shrubs, requiring moderate maintenance and occasional irrigation, characterize a semi-intensive green roof system. A typical growing medium depth for a semi-intensive green roof is 16 to 30 cm. This system is able to retain more storm water than an extensive system and provides the potential to host a richer ecology. Though higher in maintenance, this green roof system also provides the potential for a formal garden effect. When elements of both extensive and intensive green roof are found in green roof it’s considered to be semi intensive green roof.

Carnegie Mellon Hamerschlag Hall
The semi-intensive green roof at Hamerschlag Hall features a 7 cm drainage layer with a 7 cm extensive growing medium mix. The green roof supports over twenty-eight different plant species, ranging from sedums, herbaceous plants, tall grasses, and small shrubs, creating a rich and bio-diverse community for local fauna. Additionally, wood logs and strategic plant maintenance encourage the establishment of wildlife.
Figure 16

Philadelphia Public Library
The Philadelphia Public Library features a semi-intensive green roof with an accessible patio open to the public. The green roof utilizes a granular drainage system and supports a multitude of sedums, herbaceous plants, and ornamental grasses.
Figure 17

Evansville Public Library, Oaklyn Branch
Beneath its meadow surface this semi-intensive green roof features a 40 cm profile with a 10 cm deep drainage layer. The green roof creates a park like setting blanketing the library with wild flowers and blending into its natural surroundings. Not only does the depth of the green roof provide a rich environment for the meadow to flourish but it also insulates the building, significantly keeping it cooler in the summer and warmer in the winter.Figure 18
3. Extensive Green Roof:
An extensive green roof system is characterized of its vegetation, ranging from sedums to small grasses, herbs and flowering herbaceous plants, which need little maintenance and no permanent irrigation system. The growing medium depth for an extensive green roof system is typically 16 cm or less. These systems are ideal for efficient storm water management with low maintenance needs. Extensive green roofs are very cost efficient.
Extensive green roofs are lightweight with a shallow layer of growing substrate, requiring minimal maintenance. They generally have lower water requirements and use small, low-growing plant species, particularly succulents. “Ecoroofs” or “Brown Roofs” are terms used to describe these extensive green roofs. Roofs that are designed and planted specifically to increase local plant diversity and provide habitat (food and shelter) for wildlife are known as “biodiversity green roofs”.
The extensive green roof is simpler compare to intensive green roof because it’s lightweight and requires low-maintenance and drought resistant plants usually sedum species are used. Extensive green roof can weigh from 73kg/m2 to 122kg/m2 .
Looking at extensive green roof from sustainable point of view it’s considered to be more important because it has low weight and can be used in more rooftops compare to the intensive type.

Bronx County Courthouse
The Bronx County Courthouse features a 3 cm drainage layer with a 7-8 cm deep growing medium profile. The green roof is composed of a mix of sedums and hardy herbs, with a sweeping crescent of small grasses. Despite the 10 story elevation and center city location, the green roof has attracted a variety of wildlife over the years.

Benefits of Roof Gardening:
A roof garden offers much welfare, especially in a crowded urban environment. Being able to go to the green roof building and be in the open air with plants and greenery provides a refreshing change from the glass, concrete, and steel. The benefits of roof garden can be identified into two (2) parts, such as:

A) Private benefits
B) Public benefits

A) Private benefits:

A – 1. Increase roof life
Roof garden assists in increasing the expected roof life of the building. The life expectancy of a “naked” flat roof is only 15 to 25 years. UV-radiation and high Ozone ratios accelerate the ageing process, which results in, material fatigue, shrinking, crack formation, and leakage. Green Roof creates a protection layer for the waterproofing incase of mechanical damage like hail, wind, vandalism, and fireworks.

A – 2. Reduce noise levels
Roof garden can reduce sound reflection by up to 3 dB and improve sound insulation by up to 8 dB decibel. This is important for people who live near airports, noisy discotheques, or industrial parks. Additionally, electromagnetic waves from transmitting stations can be effectively shielded by the vegetation layer.

A – 3. Heat Shield
During the summer months, roof garden helps reducing the indoor temperatures through transpiration. The typical overheating of urban flats in summer can be avoided with vegetated roofs. The vegetation layer buffers the temperature stress during summer as well as winter. Therefore, the use of air conditioning and energy consumption can be effectively curtailed.

A – 4. Thermal Insulation
Roof gardens can be regarded as additional thermal insulation. It reduces the use of primary energy. Thus, it can benefice us economically by saving energy.
Green roofs reduce heat transfer through the roof and ambient temperatures on the roof surface, improving the performance of heating, ventilation and air conditioning (HVAC) systems.

A – 5. Use of space
Roof garden offers several possibilities for usage, including: natural refuges for insects and plants, recreational roof gardens, roof cafes, and sporting areas. If the technical and construction requirements of the building are met, there are virtually no limits for landscape designs with perennials, small trees, terraces, or gardens. A roof garden transforms dead space into green space.

A – 6. Save cost and increase property value
Due to the utilization of the roof property, the building owner can save costs from purchasing additional land at ground level. A gorgeous view, fresh air, and privacy are also included in the price.

A – 7. Improve social interactions and work environment
Roof garden stimulates social interactions. It promotes social contacts, exchange of ideas and thus improves the quality of life. It also increases the work environment enormously. In dense, rapidly growing urban areas, inner-city areas especially, most space is occupied by buildings and related infrastructure and the opportunities for new parks and gardens is extremely limited. Green roofs, can be used for multi-level greenery designs that connect with ground level green spaces.
There is a well-known protective effect of social relationships on health and well-being, while social isolation is a known predictor of morbidity and mortality (Nieminen et al., 2010; Pantell et al., 2013; Yang et al, 2016). Green space can play an important role in fostering social interactions and promoting a sense of community (Kim and Kaplan, 2004).
In a recent study in the Netherlands, de Vries et al. (2013) found an association between the quantity and, even more strongly, the quality of streetscape greenery and perceived social cohesion at the neighbourhood scale. In that study, social cohesion was defined as a sense of community, with a focus on trust, shared norms and values, positive and friendly relationships, and feelings of being accepted and belonging. The researchers developed an indicator of social cohesion based on questionnaire data. Conversely, a shortage of green space in the environment has been linked to feelings of loneliness and lack of social support (Maas et al., 2009a, Ward Thompson et al., 2016). Various types of urban green space have been shown to facilitate social networking and promote social inclusion in children and adolescents (Seeland et al., 2009). Neuroscience has provided evidence that place constitutes a distinct dimension in neuronal processing and so ´sense of place´ and ´place identity´, in which the social and natural environment have particular roles, are important dimensions for human health (Lengen & Kistemann, 2012). Hartig et al. (2014) underlined that the relationships between social well-being and green space are complex and, while observational research may reveal associations, the underlying mechanisms are not easy to explore. Social well-being may not be beneficially affected by green and open space that is perceived as unsafe or where people engage in antisocial behaviour, although these problems can be addressed by proper management and maintenance. There is also some evidence that provision of new green spaces in disadvantaged neighbourhoods (e.g. greening of vacant lots) can reduce crime (Branas et al., 2011; Chong et al., 2013).

A – 8. Relief from monotonous lifestyle
Roof garden appears as an agent of relief from our tedious urban lifestyle. It helps us to get relief from exhaustion to concreteness of the cities. Planting on rooftops can make urban living more self-sufficient.

B) Public benefits:

B – 1. Natural habitat for animals and plants
Roof garden can compensate for lorn green areas in cities. Roof gardens, especially low maintenance extensive green roofs assist biodiversity, as wild bees, butterflies, and beetles find food and shelter there. Even rare and protected species can be found on roofs gardens. Green roofs can also provide a link or passage across urban ‘ecological deserts’ and assist in migration of invertebrates and birds.
Designing for biodiversity requires consideration early in concept development with consider to plant species, food sources, habitat values, access points and building heights.

B – 2. Storm water Retention
Green roofs absorb and retain rainwater and can be used to manage stormwater run-off in urban environments. They can also filter particulates and air pollutants. Stormwater run-off can be reduced or slowed because it is stored in the stratum, used by or stored in the foliage, stems and roots of plants, and also evaporates directly from the substrate. Additional water storage capacity in green roof systems can be provided through incorporation of a water retentive layer or drainage layer at the base of the green roof.
Several factors influence the extent to which a green roof can reduce the volume of water runoff into the stormwater system, including depth and properties of the growing substrate, type of drainage layer used and roof slope. Plants and drainage systems are important considerations in the design of a green roof for stormwater management.

A – 3. Urban heat island effect
The temperature difference between a city and the surrounding countryside is referred to as the “urban heat island effect”. Hard surfaces in urban environments, such as concrete, brick, glass, asphalt and roofing, have a high thermal mass, collecting the sun’s heat during the day and re-radiating it slowly back into the atmosphere. This contributes to a rise in ambient temperature in cities, creating large, stable masses of hot air (urban heat islands), especially during periods of calm, still weather.
Due to global warming, the surplus heat from residential buildings, industry and traffic are leading to continually rising temperatures within urban territory. In summer this effect can reach nearly 10 °C. The urban heat island effect drastically reduces the quality of life and can have a negative effect on health of the city’s inhabitants.
Covering a roof or wall with a layer of vegetation that shades building materials, which would otherwise absorb heat, can reduce temperatures. Evapotranspiration provides cooling effects, as water is evaporated from the soil and plants and plants transpire by taking water in through roots and releasing it through leaves. Energy from the sun that would otherwise heat the roof or wall surface and increase ambient air temperatures is instead used in the evapotranspiration process, resulting in latent heat loss that lowers surrounding air temperatures.
Natural air conditioners such as green areas and park can absorb up to 80% of the heat. But, in densely populated cities green areas are rare. Roof gardens can be an alternative, as they decrease the “urban heat island effect” through the process of transpiration and humidify dry air. This process tends to create a better climate for the inhabitant of adjacent apartments and buildings.

A – 4. Reduction of dust and smog levels
Green roofs can provide to the removal of dangerous combinations of toxic substances gases from the air such as NO2, NO3, CO, volatile organic compounds and diesel exhaust gases, although their effectiveness varies with plant species and area of cover.
1 m2 of green roof can filter approximately 0.2 kg aerosol dust and smog particles per year. Plants with a high foliage density or with textured leaf surfaces that trap small particles also assist in removing particulate pollution, through dry deposition on the foliage or through rain-wash. On a larger scale, green roofs can help to reduce overall environmental heat gain (re-radiation of heat from building materials with high thermal mass), in turn improving air quality as less photochemical pollutants are produced at lower air temperatures. In interior environments, plants have been shown to have a significant capacity to reduce volatile organic compounds from the air.
A – 5. Enhance quality of life in the city
Green roofs are visually enhancing the quality of life in the cities. They are able to intersect the monotony of the concrete, grey cities and improve mental and physical health of the inhabitants. Not only in cities, but also in rural areas, roof gardens allow industry buildings to blend harmoniously with the scenery.

Downsides of Roof Garden:
Despite having remarkable welfares, roof gardening has some downsides as well. These are as follows:
1. Roof gardens can be expensive to install.
2. The roof will require special water proofing to ensure that the moisture accumulated in the soil does not seep into the building below.
3. The structure and weight of roof garden can cause problems for the building.
4. Adequate water supply and proper drainage system require high cost.
5. Poorly managed roof gardens have the risk of falling.
6. In an arid or an exposed coastal region, plants suitable for roof gardening are very limited.
7. In some urban areas, to establish larger plants or trees on roof garden is not allowed.

But at the end the benefits are majority, especially in lately condition of the big cities about pollution and smog level. The roof gardens could be a simple resolution to solve this problem.

Site analysis:
Before designing a green roof it is important to understand the characteristics of the site, as these factors will influence the feasibility and cost. This chapter explains how to evaluate a proposed location for a green roof, wall or facade. It is written for situations where there is an existing building on-site, however those planning to construct a new building can adapt it.

1. Climatic factors on-site
Climatic factors will vary with geographic location as well as with the site aspect and height and even from effects of surrounding buildings. It is important to understand the likely climate onsite in order to inform decisions about which plant species are suitable for the site. There are no hard and fast rules about what constitutes too much wind or shade or other factors; rather, These are environmental gradients (for example, low wind to high wind) and often the best approach is to estimate the worst case scenario for plant growth that is likely on-site, and design with that in mind.

1-1 Wind
Average wind speeds are greater at height than at ground level. Winds may be strong around the edges of buildings, or from the down draft caused by tall buildings. It is necessary to understand the likely wind load that a green roof, wall or facade will be subjected to, so that it can be built to withstand the forces. Wind at high elevation will also influence temperature, and wind has a direct dehydrating effect on vegetation, therefore influencing species selection and irrigation requirements. See the Freshwater Place and Victorian Desalination Project green roof case studies in this guide to learn more about the challenges of wind.

1-2 Rainfall and irrigation
It is important to establish whether rainwater or another water source can be harvested from other areas on-site, and stored to supply an irrigation system. This will avoid or minimize the need to use potable water for irrigation. It is
Useful to carry out an irrigation water demand analysis, to estimate water needs.

1-3 Solar radiation
Light intensity tends to be greater at height than at ground level. At height there are fewer structures, no vegetation to absorb solar radiation and increased reflection from adjoining building and surfaces (such as glass and light-coloured walls). Conversely, there are some roofs and walls that may receive significantly less solar radiation, due to intense shading by nearby buildings. Shadowing and shading analysis can be used to assess areas of light and shade on a site and possible changes over the year and over time.

1-4 Temperature
In urban environments temperatures tend to increase with elevation, due to the increased thermal mass of built structures and the commensurate heat gain. Assessing the likely temperature range on a site is crucial in planting design, particularly in extreme temperature events.

1-5 Microclimate
Enclosed spaces such as urban canyons can create their own microclimate where wind turbulence, pooling of pollution, humidity and temperature can be intensified. The localized climate of these areas will change the growing conditions for plants and needs to be considered when planning and designing green roofs and walls.

2. Weight loading
The load-bearing capacity of a building must be known before planning a green roof, wall or facade. A structural engineer’s advice is essential to ensure comprehensive design development, based on the building’s construction, condition and weight loading capacity. For retrofitting a green roof, wall or facade, it is important to establish early whether the installation will meet the existing structural capacity of the building, or whether this will be modified to support the installation. In some instances, it is possible to strengthen an existing roof in strategic areas (and not across the whole roof) in order to achieve the design outcome while also minimizing costs.
It is important to consider not just the weight of plants when planted but their weight at maturity, especially where shrubs and trees are proposed, as these are likely to be significantly heavier over time. The weight of saturated plants and substrate must also be included in the load assessment. Some example weight loadings of plants are provided in Tables 1 and 2.
Damage to a wall can arise from wind forces, plant load, cable tension, and human access. This is particularly important where older walls are being used and where there is a large surface area of green facade (that is, wind uplift).
For a green roof, the loads that the building structure must support include:

2-1 Dead load
The final constructed weight of all built elements and all components associated with the roof or wall assembly, including plants, growing substrate and any water held in the system.

2-2 Live load
The weight of people who will use the space, and of any mobile equipment that will be used periodically on the site, for example, maintenance (live load generally applies to green roofs, not facades or walls, however it would be appropriate on a vertical surface if a trafficable maintenance platform was built into the system).

2-3 Translent load
Moving, rolling or short-term loads, including wind and seismic activity.
3. Drainage
Sites for green roofs should be assessed for drainage. Check whether the site has primary and/or secondary drainage systems.
Primary roof drainage systems may use:

Box gutters (for near-flat roofs) or eaves gutters (for pitched roofs)
Simple waterspouts (also known as scuppers)
Outlets or box drains built into the roof

These are collector drains that are designed to flow when only partly full. Primary drainage systems are not designed to remove all of the water that falls on a roof during exceptionally heavy rain.
A green roof may require a separately plumbed secondary drainage system, also known as the overflow relief system. For flat or nearly flat roofs, primary drains are located at the lowest point of the roof: flow of water into them is promoted by positive drainage.
Secondary (overflow) drains are located at a higher point on the roof. These are designed to operate in a worst-case scenario where the primary drains are completely blocked and water builds up on the roof due to a torrential downpour of rain and/or a failure of the irrigation system to shut off. Overflow drains remove accumulated water to a depth that the roof can carry
without becoming unstable, and ensure that the roof weight loading capacity is not exceeded. For roofs with a very low parapet, overflow drainage may be achieved simply by flow over the roof edges, if accumulation of water to this height fits within the roof’s design weight loading. The need for overflow relief will be established by looking at existing performance of the drainage in conjunction with the historical data on rainfall intensity.
Removal of water from any roof surface is assisted by some degree of pitch or slope. Even roofs that look flat have a gentle fall to promote movement of water into the roof drains, to prevent ponding.
“Ponding” refers to water that remains on a roof for extended periods after the end of the most recent rain event. Recurrent ponding can cause lasting downward deflection of the roof structure, which over time may reduce the efficiency of drainage and cause the roof to become unstable. A pitch of at least two per cent reduces the risk of ponding, and a steeper pitch means the roof will drain more quickly. Strengthening the roof construction to reduce deflection may be needed.
When assessing the site and planning for the design of a drainage system, consider:
The amount of rainfall that lands directly on the site, and any that drains onto it from adjacent roofs or walls.
Length of rainfall event – estimated from historical records and forecasts of future extreme rainfall events under a warmer climate.
The speed at which rainfall will collect at the drains (determined primarily by roof pitch).
The planned capacity of drains, including the drain dimensions and diameter of gutters and drainpipes.

4. Access
Evaluation of the site should review accessibility. Temporary access will be needed for machinery, and delivery and storage of materials during construction. For green roofs or multi-storey wall and facade greening, this might involve a crane to lift materials onto the site.
Consider how people will access the installation for maintenance, viewing or standing on. This might require stairs, lifts and viewing platforms for the general public or building tenants. It may also require balustrades, cables for attaching harnesses and ropes (fixed fall protection), ladders, elevated work platforms independent of the building, or swing stages mounted on the top of the building for maintenance personnel. Access for maintenance to walls and facades can also be considered from below, in which case space for a temporary elevated work platform is likely to be required.
Access for passers-by must also be considered, as there are regulations against vegetation that protrudes onto public space, and even in the private realm it is important to be aware of hazards that can be created for people using the space nearby.

Technical and construction requirements
In general, it seems the hanging garden makes surfaces which otherwise would not be protected accessible and it is now recognized as a tool to compensate for natural surfaces subtracted by development and as an element for the reconstruction of urban ecological corridors. It also provides excellent thermal-insulating performance which refer to specific cases with variables related to local climate situation, to the quantity and the type of the materials used in the cover and the type and construction characteristic of the building.
From the manuals analyzed we can summarize the green layering are complex systems consisting of heterogeneous materials as inert products, porous layers of water storage, substrates, etc., that must meet two important requirements: allow the coverage to assume its function of defense from the weather with particular regard to the collection and drainage of rainwater and provide an environment suitable for life and sustainable development of the vegetation without requiring difficult and costly maintenance.
For this it is expected a technical design, but also the knowledge of plants and their complex interactions with environmental factors. As regards the technical design, Mario Vietti subdivides the succession of layers, starting from the base, into three types:
a) system with pots: waterproofing, foundation, flooring;
b) system for hanging gardens with a layer of classic soil for cultivation: any sloping screed, waterproofing, anti-root membrane, any separation layer and/or scroll to protect the waterproofing, drainage layer with any drainage pipes, geotextile filter layer or no-woven fabric, fertile layer;
c) system for hanging garden with a layer of lightweight cultivation: any sloping screed, waterproofing and anti-root membrane in a single layer, any separation layer and/or sliding grid roots, cultivation layer made of lapilli or supply of fertilizers.
Currently, the products have reached a high level of technology so as to allow the solution to many problems, from old cardboard bitumen to special roofing membranes made of distilled bitumen modified with reins and elastomers that provide waterproofing and resistance to the movement of expansion and construction of the structures.
Vietti stresses the sealing of the slab can be achieved without thermal insulation if the underlying environment is not heated (patios, warehouses, shelters) and with thermal insulation when the slab is above houses, offices or other heated rooms. In the first case he speaks of cold roof, which only requires the installation of a waterproofing membrane on the slab and anti-root sheath; in the second case it seems possible to have two alternatives that differ in the layers sequence: heat roof and inverted roof.
In the first, the layer which has the function of thermal insulation is placed under the waterproofing membrane, just above the slab; in the second one there is the slab, the waterproofing and the insulation on which it is laid a drainage layer interposing a separation of no-woven fabric. Some manufactures of patented systems adopt this method.

One of the main factors that should be considered in the construction of hanging garden is the load of performance (capacity), weight, which may put pressure on the ceiling support without damaging it. The maximum load capacity (carrying capacity) is determined by the designer according to specific regulations; these values take into account the probabilistic load of things, people and weather condition. Vietti, in his manual, stressed that usually, in older building the capacity of the slab in 150-200 kg/sqm, while in the new buildings they moved to 400-500 kg/sqm and there are some cases that arrive until 700-800 kg/sqm. For this reason results important to take into consideration the soil layers depth and weight.
However, to obviate the heavy of the organic soil some producers are moving towards patent systems with layers of lightweight soil cultivation. Paolo Abram states that until not long ago, the layers were made of gravel and field land, the thickness were significant and there were no protection for the roots. While today there are specific lightened substrates, filter layers with appropriate characteristics, panels for drainage with high performance that have replaced the problems of old gardens and their demanding maintenance.
In recent decades, systems and materials for the construction of hanging gardens have evolved in parallel with the development of technical and construction requirements in building industry, taking into account different aspects: cost-benefit optimization, durability, safety, the ease and speed of installation, the availability and quality of materials, the cost of construction and maintenance.
The increasing appreciation of the important services provided by the green roof has allowed the development of technologies with the support of experimentation and research. Some technicians prefer to refer to commercially identified “systems”, other either opt for the assembly of technologies from different backgrounds or try to find natural materials locally available.
Almost all systems and modern methodologies are based on the application of layers called “triple-layer” or “multi-layer” with variations, which mainly concern the characteristics of the used materials and different solutions for water management. Abram argues that in Itay