Advantages of geosynthetics on green roofs

Green roofs are the roofs of certain buildings, usually in urban areas. They are considered a precious asset, a new space for entertainment and leisure that contributes to improving the lives of people and the environment.

There are more and more constructions or buildings already built that adopt this architectural model and bring small green oases to cities. There are two types of green roofs: extensive and intensive, depending on the depth of the growing medium and the degree of maintenance required by the plant species installed. Installing a green roof on a building brings economic and ecological benefits:

Economic advantages of green roofs:

Better conservation of the roof of the building. The installation of the vegetal layer allows the construction infrastructure to be better preserved.
Water retention. Green roofs can retain up to 90% of precipitation. Much of this water evaporates and the rest flows through the sewage systems. This reduces the size of the pipes and the costs of sanitation.
Financial savings. Since the vegetative layer technically insulates the building, in conditions of high or low temperatures, the action of the roof softens the temperature of the interior of the passenger compartment. Thus, the energy cost of air conditioning is reduced.
Use for recreational purposes. A green roof on the top of a building opens the possibility of developing recreation areas, gardens, children’s parks, or sports fields.
Sound insulation. Due to their structure, green roofs improve interior spaces by producing a reduction in the acoustic impact of up to 8 dB. In this sense, they are perfect for buildings located in areas with high acoustic contamination.

Ecological advantages of green roofs:

Improvement of the urban environment. Green roofs are responsible for reducing the warming of the atmosphere and humidifying the atmosphere by creating a more pleasant climate.
Reduction of pollution. Green roofs act as a filter and retain toxic elements, which retain pollution from the atmosphere. Similarly, the soil or substrate filters rainwater by reducing its content of toxic substances.
Living space for people. There is less and less green space in cities. The development of green roofs provides positive spaces for the health and vitality of people.
They are made with recycled materials. The drainage components of green roofs are made from recycled materials, such as polyethylene or rubber, and help reduce the impact on the environment.
Contribution of vegetation. The vegetation installed performs several functions on the green roof: shade, wind protection, fire resistance, and biodiversity.

In this sense, several countries including France now have legislation according to which certain constructions must include these green roofs. In 2015, the French parliament approved a regulation that requires the roofs of new buildings built in commercial areas to be covered with green roofs and solar plates. This regulation aims to strengthen the country’s energy efficiency.

In the same way that a green roof involves many advantages, the use of incorrect materials or poor execution of the installation can lead to serious problems, such as filtrations, and therefore an increase in the economic cost. To overcome this type of situation, the use of geosynthetic materials is used. Tex Delta is a manufacturer of geosynthetics designed to waterproof green roofs. In particular, we have the following products:

GEOSYNTHETIC DLT DREN. Material composed of high-density polyethylene (PEAD), with a nodule height of 8 mm. It is responsible for eliminating hydrostatic pressure, reducing thrust, and thus increasing waterproofing.
Geosynthetic DLT DREN G. It is a honeycomb material, formed by a nodular sheet with a height of 8 mm and high-density polyethylene (PEAD). In addition, it adheres to a polyethylene geotextile that promotes filtration and improves water drainage. This geosynthetic in particular has a resistance of 200 kg/m2
Geosynthetic e DLT DREN 20 P. It consists of a perforated and nodular waterproofing sheet of high-density polyethylene (PEAD). It has a nodule height of 20 mm, and a resistance of 150 kg/m2.
GEOSYNTHETIC DLT DREN +G10. It is a material formed by a nodular draining sheet of 10 mm. Just like previous geosynthetics, it is made from PEAD (high-density polyethylene) or adhered to a non-woven or geotextile to contribute to the filtration and improvement of drainage of buried structures in which greater compressive strength is required. This type of geosynthetic has a resistance of 400 kg/m2.

The market for sustainable energy solutions is growing rapidly and geosynthetics play an important role in it. For more information about this subject, we refer you to the article on how can geosynthetic support the energy transition on our blog.

Installation of geosynthetic on a green roof.

Preparation of the roof installation space

Before laying any material, operators must clean the entire area where the green roof will be installed. This step is very important to avoid future perforations on the waterproofing layer. It will also be necessary to carry out a comprehensive control of points requiring special tasks, such as piping or pipes. In addition, a roof covering is installed on the perimeter, to prevent water infiltration on the edges of the building. In addition, low walls are built (about 25 cm high) for the boundary of the green roof on sectors that do not correspond to already existing edges. On these walls will be located the watersheds by means of rainwater flow slopes.

Waterproofing phase

In this second step, the waterproofing geosynthetic equipment is installed by thermodiffusion with an automatic and manual electric torch, according to the requirements of the construction site. Grids and pipes must be reinforced with a bitumen waterproofing membrane. Recall that Tex Delta geosynthetics are equipped with an adhered geotextile acting as a mechanical protector. This asphaltic membrane is laid over the entire perimeter by roof garment, and it is sealed. Once the waterproofing tasks have been completed, a 72-hour hydraulic test will be performed.

Draining layer and sewer details.

On the geosynthetic gel layer, a layer of expanded clay 10-20 cm in diameter is placed, which drains the system. To ensure the correct conservation of rainwater flows and the drainage system, the installation includes a masonry ledge that raises them to a height of 23 cm, trying not to hinder the lateral drainage of infiltration. The entry of water to the lower grid is through hollow bricks protected by a geotextile, in order to avoid the passage of elements that can clog the pipes. On the layer of clay, beads are laid another layer of geotextile, the purpose of which is to prevent the drainage of the substrate and the introduction of roots to the layer of clay beads and the inner slab.

Substrate and watering system

On this last layer of geotextile, 15 cm of the substrate is laid. Then, if necessary for the project, an automated drip irrigation system is installed.

Planting plant species

If the irrigation system has been installed and tested, different plant species will be planted. In this case, it is better to install the plants as soon as possible because it is important that the substrate spends as little time as possible in the open.

Considerations If one wishes

to install a green roof on an already existing building, and in operation, the project involves a certain complexity because, once the installation of the green roof is completed, problems derived from water infiltration through the roof could appear. In addition, it involves the handling and transport of a large amount of soil and plant species.

GEONIK co. is a corporation engaged in the research, production, and sales of geosynthetics since 2001, the company has a strong scientific research team, advanced production infrastructure and processes, strict quality management systems, and advanced cost control systems.