Green roofs have become increasingly popular in recent years as people look for ways to reduce their carbon footprint and make their homes more environmentally friendly. By the end of this article, you will have a better understanding on the different types of green roofs and their benefits which can help you choose the best option for your needs and budget.
What is a Green Roof?
A green roof is a layer of vegetation that is grown on top of a building, replacing the traditional roofing materials.
Not only do green roofs provide an attractive and natural look, but they also offer a range of benefits such as improving air quality, reducing energy consumption, and providing insulation.
The implementation of vegetation on rooftops, known as green roofs, has a long history, initially serving as a method for thermal regulation. The use of green roofs for this purpose took advantage of the natural insulating properties of plant life.
Distinct from intensive roof gardens, extensive green roofs are characterized by a thinner and lighter profile, resulting in a more resource-efficient and natural system. The vegetation selected for extensive green roofs typically demands minimal water and maintenance, contributing to their economic and ecological advantages.
Consequently, the extensive green roof concept has witnessed continued adoption and has steadily gained traction in various regions across the globe.
Different Types of Green Roofs
There are several different types of green roofs, each with its own unique characteristics and benefits. The most common types are extensive, semi-intensive, and intensive. Let’s look at each in more detail.
Extensive Green Roofs
Extensive green roofs are the most common type of green roof. They are lightweight and require minimal maintenance. The growing medium for extensive green roofs is typically shallow, ranging from 60-200mm in depth, and supports a small variety of flora and fauna.
One of the most common plants used for extensive green roofs is sedum. Sedum plants are drought-resistant and have thick leaves that store water, making them ideal for minimizing moisture loss. Other plants that can be used for extensive green roofs include herbs, grasses, and wildflowers.
The weight of an extensive green roof ranges from about 13 to 30 pounds per square foot, making them the least expensive green roof type. Extensive green roofs are often installed on existing roofs and can add 10 to 35 pounds per square foot to a roof’s load, depending on the source.
Extensive green roofs provide numerous benefits, including reducing energy use across different climates. The amount of cooling provided by the green roof depends on the type of material used for the roof. Extensive green roofs can also help reduce stormwater runoff by absorbing rainwater and releasing it slowly. Additionally, they can help improve air quality by absorbing pollutants and reducing the urban heat island effect.
Overall, extensive green roofs are an excellent option for those looking to add green space to their roofs while minimizing maintenance and cost.
Intensive Green Roofs
Intensive green roofs are the most complex and expensive type of green roof. They are designed to support larger and heavier plant structures, such as trees, shrubs, and even small gardens. Intensive green roofs require more soil depth, irrigation, and maintenance than extensive green roofs.
One of the benefits of intensive green roofs is their ability to replicate a natural landscape and create walk-through habitats in urban areas. They also provide excellent insulation, drainage management, and temperature regulation. Moreover, they can be used for agricultural purposes.
However, intensive green roofs have a greater impact on the structural design of a building. They require the deepest soil and have the highest weight load, which can be a challenge for some buildings. Additionally, they need more maintenance, irrigation, and fertilization, which can be costly.
According to the Soil Science Society of America, intensive green roofs offer more cooling and energy savings benefits than extensive green roofs. The increased soil depth and plant density of intensive green roofs prevent heat from moving down to ceiling height. Energy use can be reduced by 10 to 30 percent when a building has a green roof.
In summary, intensive green roofs are a complex and expensive type of green roof that can support larger and heavier plant structures. They provide excellent insulation, drainage management, and temperature regulation, and can be used for agricultural purposes. However, they require more maintenance, irrigation, and fertilization, and have a greater impact on the structural design of a building.
Semi-Intensive Green Roofs
Semi-intensive green roofs are a type of green roof that falls somewhere between extensive and intensive green roofs. They require a deeper soil layer than extensive green roofs but not as much as intensive green roofs. The soil depth for semi-intensive green roofs ranges from 6 to 12 inches.
Semi-intensive green roofs are characterized by herbaceous plants, perennials, ground covers, grasses, and small shrubs. These plants require more maintenance than those found on extensive green roofs but less than those found on intensive green roofs.
Semi-intensive green roofs require occasional irrigation, depending on the location.
One of the advantages of semi-intensive green roofs is that they offer more design options than extensive green roofs. In addition to the mosses, grasses, and sedum of extensive roofs, semi-intensive plantings include herbs, flowering plants, taller grasses, and small shrubs.
Semi-intensive green roofs can provide a more biodiverse habitat for insects and birds than extensive green roofs. They also offer more aesthetic value than extensive green roofs due to the variety of plant options available.
Overall, semi-intensive green roofs are a good option for those who want a green roof that is more aesthetically pleasing than an extensive green roof but requires less maintenance than an intensive green roof.
Different planting systems on Green Roofs
Ready-to-Place “All-in-One” Green Roof System
The modular green roof system incorporates all essential layers of a green roof (drain, filter, growing medium, and plants) into one convenient unit, referred to as a tray, module, or paver.
These easy-to-use, pre-planted trays offer a quick and low-maintenance solution for installing a lush green roof.
As of 2014, it remains the only all-in-one pre-planted module approved by building professionals and is suitable for various roof types, including flat roofs and those with a pitch of up to 200%.
Sedum Mat Pre-Planted Systems
The mat-based vegetated system consists of a roll grown in an open field, unrolled, and laid directly on the layer of the growing medium along with the standard layers of a system (drain, filter).
Pre-planted mats enable immediate vegetation of the roof and can be installed at nearly any point during the growing season.
Vegetated Systems based on Plugs or Potted Plants
Vegetated systems based on plugs or potted plants allow for a diverse array of plants on the green roof. This system can be established in spring or autumn to optimize plant rooting in the growing medium.
The plant cover level reaches 80% after a period of 12 to 24 months.
Cutting–Based Vegetated Systems
Cutting-based vegetated systems are particularly well-suited for large-scale projects (over 1000 m²). Quick and easy to use, the plant cover level reaches 80% after a period of 18 to 36 months.
Want a Green Roof Installed?
Green roofs are a sustainable and eco-friendly way to improve the environment and reduce energy costs. There are three main types of green roofs: extensive, semi-intensive, and intensive. Each type has its unique characteristics and requirements.
When choosing a green roof, it is essential to consider the building’s structure, location, and purpose. Factors such as weight, drainage, and maintenance requirements should also be taken into account.
Green roofs have numerous benefits, including reducing stormwater runoff, improving air quality, and reducing energy costs (up to 75% deduction in some cases). They are a valuable addition to any building and contribute to a healthier and more sustainable environment.
If you need help with choosing between the different types of green roofs, get in touch with one of our experts, and we will help guide you.