How sustainable is a green roof really?
Posted on Monday 29 July, 2024In recent years, sustainability has been the key word in construction. Sustainable construction or renovation is actually no longer an option, it is a requirement. From 2020, according to European legislation, only sustainable houses may be built. When choosing your building materials, you want to be sure of course, that they really are sustainable. You may have heard that a green roof is a sustainable choice for a roof renovation or new construction project. But just how sustainable is a green roof? In this article, we zoom in on the ecological and economic value of a green roof and give an overview of all the certifications available in the field of sustainable, bio-based or circular construction.
What is a green roof?
Let's start at the beginning; what is a green roof? A green roof, Sedum roof or vegetation roof is a roof where vegetation, i.e. plants, are installed on top of the waterproofed roof covering. There are many different types of green roofs. The choice for a specific type of green roof depends on the structure of the roof (flat or sloping), the load-bearing capacity of the building (do you need a lightweight green roof, or can the roof support a heavier green roof), the type of planting (Sedum, grass, herbs) and the purpose for which you want to install a green roof (biodiversity, water storage, solar energy generation). As you can see, there is a lot to choose from when it comes to a green roof.
Not sure which green roof to choose for your project? At Sempergreen, we can advise you on the best green roof construction for your project.
A bumblebee finding nutrition on a Biodiverse green roof
What are the benefits of a green roof?
Good news! A green roof has many advantages for people and the environment. A selection of the many benefits: a green roof strengthens local biodiversity, buffers rainwater during extreme rainfall, increases the efficiency of solar panels, purifies the air of fine particles and converts CO2 into oxygen, reduces noise pollution through the dampening effect of the plants and has a positive effect on people's well-being. And that's not all. There are also economic benefits of a building with a green roof. Thanks to the greening, the value of the building increases. Would you like to read more about the advantages of a green roof? Then click here.
How does a green roof make my building more sustainable?
Installing a green roof on a building contributes to a more sustainable building in several ways. In the previous paragraph, you already learned about the various environmental benefits a green roof provides.
In addition, if a green roof is applied to it, the roofing will last years longer. Vegetation protects a bitumen roof covering from the harmful effects of the sun. Bitumen actually ages faster under the influence of the sun. It also drastically reduces the impact of wind, rain and temperature changes on the roof covering. With a green roof, you can extend the life of your roofing by decades (sometimes up to 60 years!).
Do you intend to combine your green roof with solar panels? Then your green roof will increase the efficiency of the solar panels by 6-10% and reduce your energy costs at the same time. This is because the plants lower the ambient temperature, and solar panels work better and more efficiently at lower temperatures. So that's twice as sustainable!
In doubt between solar panels or a green roof? No need to choose anymore with a Solar Green Roof! This sustainable roof combines a (lightweight) Sedum roof with solar panels. The perfect combination of high energy yield and 100% space for greenery!
What sustainability certifications can be achieved with a green roof?
Sustainable construction is all about the environmental impact over the entire life of the building. This means during all life stages from the design, construction, and use till the renovation or demolition of the building. When building sustainably, you also want to be able to prove this to the outside world. For instance, because your buyers or tenants ask for it. You can prove the sustainability of your building with a sustainability certificate. Do you want to obtain a sustainability certificate for your project? Then installing a green roof always has a positive effect on gaining points for a certificate. A sustainability rating system always looks at a series of measures taken in a project. The application of a green roof is one of them.
In the field of sustainable construction, there are several certificates. We list them for you below:
1. LEED – integral sustainability
LEED stands for 'Leadership in Energy and Environmental Design' and is the most widely used green building rating system for new and existing buildings worldwide. LEED aims to create better buildings and provides a framework for building owners and operators to create environmentally friendly and resource-efficient buildings. The certificate was developed by the US Green Building Council (USGBC) and has become an internationally recognised standard for green building certification. LEED certification is based on a rating system, where buildings earn points for various sustainable strategies and practices, such as:
- energy efficiency
- protect and restore water resources
- protect and enhance biodiversity and ecosystem services
- the use of renewable materials
Projects are assessed by GBCI and awarded points. These points determine the LEED certification level of your project: Certified (40-49 points), Silver (50-59 points), Gold (60-79 points) or Platinum (80+ points). Applying a green roof earns you valuable points within LEED. This is because a green roof can contribute both to energy efficiency, water savings and the promotion of biodiversity.
Example LEED certified project, Skanska HQ
2. BREEAM – integral sustainability
BREEAM stands for 'Building Research Establishment Environmental Assessment Method' and is considered the most popular building certification within Europe. With this method, projects can be assessed for integral sustainability. The BREEAM framework is used to assess whole life performance, from new build projects to refurbishment and fit-out. The methodology differs per European country, as climatic conditions and laws and regulations differ, making customisation per country important. BREEAM has four labels: for new construction and renovation projects there is BREEAM New Construction (and Renovation). Existing buildings are assessed with In-Use, demolition projects with Demolition and Dismantling and entire areas with BREEAM Area. A green roof on your project will earn important points for your BREEAM certification. The percentage of the building's footprint that is implemented as external green space, which enhances its ecological value, is assessed.
Example project with BREEAM certification, Royal Wilanow
3. nZEB - Nearly-zero energy and zero-emission buildings
As Europe’s largest energy consumer - buildings have a critical role to play in achieving the EU’s ambition of becoming the world’s first climate-neutral continent by 2050. From 2020, all new buildings in the EU are required to be ‘nearly-zero energy buildings’. This will be replaced by a further enhanced ‘zero-emission buildings’ requirement, starting from 2028 for new buildings owned by public bodies and 2030 for all other new buildings.
Nearly-zero energy buildings (nZEB) is a requirement introduced by the Energy Performance of Buildings Directive. It means that all new buildings – as of 2020 - must have a high energy performance and very low-energy needs, covered largely by onsite and nearby renewable energy sources. The European Commission’s Joint Research Centre found that this requirement will improve the energy performance of new buildings in the EU by 70%, compared to 2006.
Applying a Solar green roof from Sempergreen has a positive impact within nZEB, as energy generated by solar panels falls under renewable energy. Moreover, the greenery on the green roof has a heat-regulating effect. In this way, the Solar green roof helps sustainable building projects achieve nZEB energy performance.
Future of green roofs and sustainability
The development of green roof systems is constantly evolving. Besides the traditional green roof, there are now also green roofs that focus specifically on storing excess rainwater due to extreme weather, or green roofs combined with solar panels for sustainable energy generation. For pitched roofs, there are both vapour-proof or vapour-permeable solutions, which can act as an alternative to the traditional roof tile. For buildings with a supporting structure, which can carry little weight, there is the lightweight green roof structure. Instead, if you want to contribute to the local biodiversity of your building, choose a biodiverse green roof. Whichever type of green roof you choose, all these green roof types contribute to the various building certifications in several ways. So, with a green roof, you are always in the right place when it comes to sustainability!
Would you like to know more?
Our green roof specialists will be happy to tell you more about the sustainable aspects of a green roof. Please contact us without any obligation using the button below.