RoofX features a layer of soil and vegetation on an impervious surface. They’re a great way to reduce energy costs and extend the life of your roof.
They can be ‘extensive,’ featuring only a thin growing medium, or ‘intensive’ with more than 200mm of soil and vegetation up to the size of trees.
Green roofs can significantly reduce carbon dioxide emissions from buildings. They do so by absorbing greenhouse gases through their vegetation and storing them in the roots, stems, leaves, and other parts of the plants. They also lower energy consumption because the plant cover provides a thermal barrier between the building and the outside air.
Green rooftops absorb and slow stormwater runoff, which prevents excess water from flooding sewage systems. This reduces sewage treatment costs and makes for cleaner rivers, lakes, and streams. Furthermore, they provide habitat for animals, which can be especially important in cities where fewer natural spaces exist.
A green roof can take the form of a meadow, garden, or other landscape, depending on the design preferences of the building owner. They can include grass, shrubs, and even trees. They typically use high quality waterproofing, a root repellent system, drainage system, filter cloth, lightweight growing medium, and plants.
As the urbanization of cities continues, there is less and less available land for green space. In addition to adding aesthetics, a green roof can be used as a recreational area for the public. The University of Denver incorporated one on its Community Commons building, which features native species and offers residents an opportunity to relax and enjoy the outdoors.
A study assessing the effects of different plants on green roofs found that Sedum acre, Frankenia thymifolia, and Vinca major had the best potential to reduce a building’s energy demand and carbon emissions. Using Design Builder software, the researchers calculated that a roof covering all of these plants could save about 8.5% of a typical building’s annual energy consumption.
However, the authors pointed out that a green roof’s ability to reduce carbon emissions only lasts for a year or two before the emitted carbon from the breakdown of soil and plant material balances out the reduced energy consumption. They also added that the embodied carbon of the construction materials used must be taken into account, as well as the energy required to grow and transport the plants.
They calculated that for extensive roofs, it would take between 50 and 61 years to recoup the monetary investment in green roofing through energy savings.
In cities, where many buildings are built close together in a compact space, the high density of heat-absorbing materials and concrete leads to them being hotter than surrounding areas. This has become known as the Urban Heat Island effect and is a significant contributor to the city’s climate change impacts. By incorporating vegetation and providing a cooling surface, green roofs help to mitigate this effect.
The plants on a green roof absorb sunlight, reflect it back and absorb some of the sun’s heat reducing the overall temperature of the building. As a result, they also reduce the need to air-condition the interior and so save energy.
A range of different planting options are available depending on the design and purpose of the green roof, but they generally involve a combination of sedum blankets, a layer of lightweight growing medium and plants. The plants can be manicured and elegant, such as in the case of a rooftop garden at a hospital, or they can be left wild and free, like an outdoor room in a park.
By filtering rainwater before it is discharged, green roofs can help to reduce water runoff and prevent flooding in local communities. They can also help to reduce the amount of wastewater entering sewer systems, which will lead to less pressure being placed on drains and overflows.
In addition, green roofs act as a habitat for wildlife and nature, encouraging biodiversity in urban areas where there are few places for plant and animal species to thrive.
In one study, researchers investigated the effects of a green roof on its users, by looking at the link between frequency and duration of use, and various social impact measures. This research showed that people who used the green roof regularly, or visited for 30 minutes or longer, reported significantly greater levels of social wellbeing, attachment to place and mood state than those who did not visit the green roof as often. The findings of the study were supported by a range of statistical analyses.
Green roofs can add a whole new element to any building and can be a fantastic design feature to an otherwise barren part of the landscape. The presence of natural elements on a roof brings colour, variation and stimulation to an otherwise featureless space that can become a place where people gather and relax. Studies have shown that people have a natural affinity with nature and the presence of trees, plants, grasslands and water bodies can reduce stress levels and promote positive wellbeing.
Many urbanized areas have very little accessible or visible green space. This lack of opportunity to experience nature’s involuntary stress-relieving power can place individuals at risk of poor productivity and anti-social behaviour. By providing an environment in which birds, insects and other wildlife can thrive and find shelter and food, green roofs help to introduce the ‘natural’ to an urban landscape that has largely been reclaimed by buildings.
Increasingly, green roofs are being used to create recreational space for the public, particularly in cities that do not have parks. Often these spaces are designed to facilitate the use of recreation facilities such as swimming pools, tennis courts and playgrounds. They also provide a venue for community groups to engage in active recreation such as vegetable growing and gardening.
For smaller, lower-sloped sites, the extensive green roof option is often the best choice. These can be suitable for garages, garden offices, sheds and extensions, as well as more sedentary uses such as seating or viewing.
These types of green roof are typically suited to a variety of plant species, but the selection should be based on site suitability and the type of activity that is planned. The vegetative components of a green roof need adequate drainage and water management, and the system will require regular inspections.
Some green roofs are seeded to increase their biodiversity potential, and this is particularly common in locations where the prevailing climate is not suitable for more demanding vegetation such as trees. This practice is controversial and has been criticized by purists, but it does offer a way to bring the benefits of the urban green space to more places in the city where such opportunities would not usually be available.
Green roofs are a great stress reliever for building occupants. The soothing environment helps to calm the senses and can be a great place for meditation. Additionally, the plants and soil on a green roof provide a variety of nutrients and can help to lower blood pressure, all of which contributes to reduced stress levels.
Having a green roof on your building can also reduce the noise pollution created by cars, trains and planes. The acoustic properties of the soil and vegetation in the growing medium are very effective at dampening sound waves. Studies have shown that 5 inches of growing media can reduce noise by up to 40 decibels.
Since green roofs are a combination of living and structural elements, they add a significant amount of weight to the structure below. Therefore, they require additional support to ensure their long-term stability. This is particularly important in a seismic zone where the added weight can increase the chances of damage caused by an earthquake. To mitigate this risk, it is crucial that a professional evaluates whether the existing roofing can adequately support an extensive or intensive green roof.
The plant life on a green roof absorbs the sun’s heat, which helps to keep the space cool. This natural cooling process, known as evapotranspiration, reduces the urban heat island effect that causes cities to become sweltering hotter than surrounding rural areas.
As a result, green rooftops can be used as an alternative to air conditioning and may be able to save energy costs in the long-term. Furthermore, green roofs are a great alternative to traditional landscaping for commercial buildings, offering a unique opportunity to create an attractive and engaging public space while helping the environment.
Moreover, green roofs are a unique habitat for wildlife in urban environments where nature is often pushed to the periphery. This can allow birds, insects, and other animals to find shelter and food in areas where it would otherwise be difficult.
As people spend more and more time indoors, the need for access to outdoor spaces that are rich in natural scenery becomes increasingly important. This can help to improve mental and physiological health, which in turn leads to increased productivity and a happier work environment.