Like everything in construction, whatever is poorly designed, installed or poorly maintained, can be problematic.

In the history of green roofs, there is no history of failure in roofs designed and installed according to good standards, namely the Technical Guide for Green Roofs, adapted to the Portuguese reality, very inspired by the German FLL guidelines.

If the project is developed according to the good rules of design / construction and maintenance of green roofs there will be no problem.

However, the most common problems due to design and / or execution and / or maintenance failures are:

_ Use of soil instead of technical substrates: The use of soil instead of technical substrates in modern, multilayer systems with low thickness leads to the loss of the structure of the soil profile, clogging of filters and waterlogging in the rainy season with the consequent death of the plants. In extreme cases it can result in overloads that lead to serious damage to the structure of the building that can, in the end, result in its collapse. It should be noted that the soils in Portugal are mostly clayey and as such lead to the rapid filling of the separation and drainage areas / filters causing the failure of the entire system.

The theme of substrates is so important that Neoturf has another project financed by the European community for research in this area between 2018 and 2021 (global budget over 500,000 euros)

_ Drainage: Drainage problems are common, the consequences being the death of plants and problems of localized overloads with deformation in the structure. In order to avoid these problems, it is recommended that the drainage can be specified by a specialist for each case study. 

_ Structure: Modern systems for green roofs have brought significant advances in reducing the weight of green roofs. However, it is always necessary to take into account the technical specifications of the product / manufacturer and the load capacity of the building, to prevent cracking or even the collapse of the structure. The load capacity of the structure should be the first question when designing a green roof .

_ Death or poor development of plants: Problems with plants are usually associated with scarcity or excess water (drainage problems that cause root asphyxiation). It is important that species are carefully selected on a case-by-case basis according to the type of use and maintenance thought for the cover and also the type of cultivation system used.

Green roofs offer benefits at different levels. The main ones are:

_ Rainwater retention capacity,

_ minimizing flood and flooding problems in peaks of precipitation

_ Improvement of the microclimate and consequent reduction of the heat island effect;

_ Promotion of the improvement of air quality, through the capture of CO2, production of oxygen, as well as through the retention of dust and particles suspended in the air

_ Decreased noise

_ Promotion of biodiversity

_ Reduction of energy costs due to the thermal insulation they provide to buildings

_ Reduction of building maintenance costs by protecting waterproofing and reducing energy costs;

_ Increase of useful space in the city

_ Real estate valuation

_ Possibility of producing fresh local food
 

To distinguish green roof prices, we have to understand that this price varies a lot depending on the conditions of each project.

In order to be able to systematize information, we must start by distinguishing prices between types of green roofs: extensive and intensive.

On average, extensive green roofs in Portugal can cost between 60 and 90 € / m2 (VAT not included), and intensive green roofs can cost between 90 to 190 € / m2 (VAT not included).

These values ​​are merely indicative averages, which are based on the projects already carried out by Neoturf since 1999, and should undergo adjustments, sometimes important that are justified with gains or losses of scale and logistical issues of access to coverage and means for distribution of materials in roof.

Prices also vary widely according to the quality of the system to be installed, as they are not all identical although, apparently, they often appear and are presented commercially as such.

Offers at lower prices should always be technically very well explained.

Unfortunately it is possible to make a green roof that works relatively well during the 5 year warranty and then becomes a nightmare of problems. .

In case of doubt, consult the technical guide for the green roof project /construction and maintenance launched by ANCV (National Association of Green Roofs) with the support of the Order of Engineers in the Centro region.

Green roofs have three categories:

Extensive green roofs:

Coverage of buildings or other constructions with a vegetation layer that requires low thickness and substrate, small vegetation and little maintenance, once installed. The plants of the extensive green cover (succulents, perennial herbaceous) grow on a layer of substrate with a maximum thickness of 15 cm and, in general, the vegetation does not exceed 50 cm in height. The weight of the substrate profile and vegetation as a whole is generally less than 150 kg / m2. In Portugal these coverings must be watered, at least during the first year and whenever justified.

Intensive green roofs:

Gardens over buildings or other constructions that have an intensive treatment plant cover requiring maintenance identical to that of a conventional garden. Intensive green cover plants can be herbaceous, sub-shrubs, shrubs and trees. They develop in a layer of substrate with a thickness greater than 25 cm. The combined weight of the substrate layer and vegetation is greater than 250 kg / m2.

Semi-intensive green roof:

Roof of a building or other constructions that present a mixed vegetation cover (intensive and extensive) and that requires moderate maintenance. The vegetation of a semi-intensive living cover is generally composed of herbaceous, sub-shrub and shrub plants. They develop in a layer of substrate with a thickness between 15 cm to 25 cm.