Green roofs are an exciting trend in the roofing industry. Installing a green roof is an excellent way to reduce energy costs, improve building insulation, and save money. Having a vegetation blanket on top of a building also has a broader environmental benefit. Ultimately, this design creates a sustainable environment. It reduces heat islands, improves the landscape, lowers carbon emissions, and manages storm water runoff.
But before you replace your roof by laying turfgrass on it, there are several factors to consider about green roofs. For example, precisely what is it? How does it work? And what are the benefits of having grass and other vegetation growing on your roof?
What is a Green Roof?
A green roof describes a building with a roofing system consisting of a layer of vegetation. Also called a living roof, biodiverse roof, vegetative roof, or eco-roof, the roof can be flat or sloped and consist of a waterproofing membrane, drainage and irrigation systems, and a root barrier.
The depth of the vegetation layer depends on several environmental factors.
Green roofs can also include the following:
- Cool roofs use reflective surfaces to direct heat away from the building.
- A rooftop pond can treat greywater.
- Solar photovoltaic panels or thermal collectors for energy savings.
Emerging Environmental Trends in the Roofing Industry
Green roofs are one of the most exciting trends in the roofing industry. With more people worried about the changing climate, many see that living roofs could help address some concerns. And it’s not just energy conservation and reducing utility bills that property owners are concerned about. Green roofs are becoming more popular in urban areas where ground-level public green spaces are rare.
For example, according to data, the size of the green roof industry globally was $1.1 billion. Growth in the sector is expected to grow by 17 percent from 2020 until 2027. Additionally, many large cities offer building owners tax incentives for green roof installation systems or solar photovoltaic panels.
How Are They Made?
The definition of a green roof varies depending on the type of vegetation system in place. Generally, a living roof requires a waterproof membrane to prevent dampness in the building. Then, there are additional layers like a drainage layer, irrigation system, drainage layer, and growing medium.
The US National Park Service says three types of green roofs are extensive, semi-intensive, and intensive. Here is a brief overview of these categories:
- Extensive roofs: This type has a thin growing medium and has minimal watering requirements for a limited range of plants. This solution is suitable for many buildings because it is lightweight, low maintenance, and is relatively inexpensive to install.
- Intensive roofs: This system uses a deep growing medium and supports a diverse range of plants and small trees. The green roof space is visually attractive and can allow the roof space to be used for other purposes — recreation and growing food.
- Semi-intensive: This type of vegetated roof includes the features of an extensive roof and intensive green roof.
Typically, green roof technology uses a growing medium consisting of mineral aggregates and only a small amount of organic matter. This ensures the medium doesn’t become compacted and remains chemically and physically stable.
There are several environmental, financial, and aesthetic benefits to installing a green roof.
Here are six benefits of “roof greening” for commercial and residential buildings.
1. Increased energy efficiency
A building with a grass-covered roof significantly reduces the energy required to heat and cool the building. The extra layer of natural insulation prevents the building from heating up in summer. In addition, it keeps heat in the building during winter, resulting in lower energy bills.
2. Better rainfall and stormwater management
Green roofs are ideal for managing precipitation. For example, they retain up to 90 percent of rainfall during summer, and in winter, 40 percent. Much of the water evaporates as the plant life on the roof “breathes.” Additionally, they prevent water surges during storms that stress sewer systems.
3. Reduce the urban heat island effect and improve air quality
A rooftop garden or green space helps to reduce average summer temperatures in large cities and built-up areas. Typically, a green roof temperature is between 30°F and 40°F lower than a conventional roof. This means that the ambient temperature in urban areas can be reduced by around 5°F.
4. Additional environmental benefits
Eco-roofs are an excellent way to reduce the impact humans cause on the environment. For example, reducing greenhouse gas emissions is easy because loads on HAVC systems are lower. Additionally, green roofs last longer, meaning that there is less waste for landfill
5. Develop new amenity spaces
An accessible green roof provides urban green space and improves the comfort and enjoyment of the building’s occupants. There are several ways to use a green space on top of a building. Here are a few examples:
- Having a includes herb and vegetable garden for use by the building’s occupants or the community.
- Create a relaxing recreational space with a children’s playground, yoga, or outdoor gym.
- Use the space for a hospitality area with cafes and restaurant terraces.
- Improve the well-being of office staff and have outdoor work areas.
- Beautify your building’s aesthetics and attract wildlife to urban environments like bees, butterflies, and pollinators.
6. Increased biodiversity in an urban landscape
One of the significant advantages of a green roof is its environmental impact in large cities. Green roofs support a variety of plants, birds, and insects that would otherwise be missing from urban areas. Additionally, the green spaces provide a place for migrating birds and help link species that would otherwise be fragmented.
Installing a Green Roof
Installing a living roof is a significant undertaking. So before thinking about planting vegetation on your property’s rooftop, it’s vital to consider several factors. These include the roof slope, the building’s structural load capacity, and roof construction materials.
Another consideration when installing a green roof is to ensure the type of plants, irrigation system, waterproofing, and drainage system is suitable for the local environment and climate.
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