Green Roofs

Green roofs, vertical gardens, and green facades are a growing architectural trend, particularly in Norway, Denmark, Switzerland, and the Netherlands. In Poland, they are also gaining popularity, with numerous innovative solutions emerging in recent years.

A green roof is a surface separated from the ground, located not only at an elevated height but also at ground level, such as on parking lots or walkways. Green roofs offer numerous benefits, including reducing the urban heat island effect by lowering temperatures in concrete city centers. They also create habitats for insects, birds, and small animals. The increased presence of greenery in urban areas positively impacts residents’ well-being, providing relaxation and recreation spaces while improving air quality. As a result, local governments are increasingly supporting these ecological initiatives, with some even offering property tax exemptions.

Choosing Plants for a Green Roof

A green roof enhances the durability of roofing layers, and when professionally installed, it can remain in excellent condition for decades. The choice of vegetation depends on the type of green roof—extensive or intensive. Extensive green roofs are best suited for plants with low water and soil requirements, such as succulents, mosses, and sedums. In contrast, intensive green roofs can support a wider variety of plants, including grasses, flowers, shrubs, and even trees.

Benefits of a Green Roof

Green roofs offer many advantages. Beyond their aesthetic appeal, they provide recreational space, purify the air, retain rainwater, and reduce noise pollution. Economically, they lower energy consumption and extend the lifespan of roofing membranes, thereby increasing property value.

Due to their environmental benefits, many city governments support the construction of green roofs by offering tax reductions or subsidies. Cities like Vienna are leading the way in urban greening by providing financial and advisory support. In the coming years, an increasing number of green facades, roofs, and courtyards are expected, contributing to improved urban living conditions and environmental protection.

Layers of a Green Roof

A green roof consists of several layers that together create a stable and functional environment for plant growth. The structure can be broken down as follows:

Waterproofing Layer – The first layer consists of a root-resistant waterproofing membrane. Options include TPO/FPO membranes, EPDM foils, bituminous coatings, or roofing felt. For intensive green roofs, EPDM foil is recommended due to its superior resistance to root penetration.
Protective Fleece – This layer protects the waterproofing membrane from mechanical damage and is usually made of PES/PE fleece with a weight of up to 300 g/m².
Thermal Insulation – In inverted green roofs, XPS insulation is used, followed by a diffusion membrane (e.g., Delta Vent RR) to separate it from the drainage layer.
Drainage Layer – This layer facilitates water drainage while retaining moisture for plant growth. Available materials include HDPE retention-drainage mats, EPS dimpled mats, HIPS retention-drainage mats, PP retention boxes, or mineral drainage systems, all offering high compressive strength and water retention properties.
Filtration Layer – Positioned between the drainage and vegetation layers, this prevents soil particles from clogging the drainage system. Typically, PP fleece with a weight of 100-200 g/m² is used.
Vegetation Layer – The top layer consists of specialized substrates tailored to the specific green roof type and the plant species to be cultivated.

Essential Materials for Green Roof Construction

To construct a green roof, the following materials are required:

Waterproofing: TPO/FPO membranes, EPDM foils, or roofing felt (EPDM is recommended for intensive green roofs).
Protective fleece: PES/PE fleece.
Thermal insulation: XPS panels.
Diffusion-separating mat: e.g., Delta Vent RR.
Drainage layer with filtration fleece: e.g., Delta Floraxx Top.
Specialized substrate suitable for the chosen green roof type.

Flat Roofs

Formwork - Shuttering