Green roof systems explained by experts – including sedum roofing
You may have first come across green roof systems on commercial buildings in cities across the US, but they’re not just a great option for these types of buildings and built-up urban locations.
A green roof is also a fantastic asset to a home, wherever you live. While it may look attractive, that’s far from the only benefit and it can bring you a host of benefits that commercial building owners have already come to appreciate.
A sedum roof is a popular choice, but certainly not the only planting option. Use our guide to discover all the possibilities of green roof systems, how they can benefit different homes, especially DIY plus, the cost of one of these with tips from the experts.
Green roof systems
There are many reasons why green roof systems are a good idea. They can reduce stormwater runoff, help cool your home, purify the air and support the beneficial insects you want in your backyard.
A green roof also brings extra color and interest and makes the view from your home and garden more attractive.
What are the different types of green roof systems?
The main types of green roof systems are extensive, intensive and semi-extensive or semi-intensive in between.
‘Green roofs are widely labeled based on the thickness of the growing media,’ explains plant expert and residential wall specialist Gennaro Brooks-Church Eco Brooklyn. ‘Green roofs use a specially mixed growing medium that works like soil, but is much lighter. The three general categories are expanded for growing media from 1 to 4 inches thick, semi-intensive for 4 to 6 inches thick, and intensive for anything thicker than 6 inches.
About where each type of green roof can be used and what it is planted with, certified roofers and House Grail roofing expert Orlando Ferris explains:
‘Extensive green roof systems are the most popular because they are easy to maintain and lightweight. Sedum, delosperma and sempervivum are most commonly used for green roofs because they fit almost every solar level and media depth in the US and can store excess water.
‘Extensive roofs can be built on a wide range of structures: single-family homes, commercial buildings and light industrial sites. As a rule, however, they are not used for publicly available zones.
‘When it comes to semi-intensive green roof systems, a deeper soil layer and drainage solution is required. This allows you to use a wider selection of more complex plant mixes, such as herbs, flowering plants, taller grasses and small shrubs.
“Semi-intensive roofs are often used in high-visibility areas to enhance the visual appeal of a building. Due to the vegetation and substrates used, they require more care than large roofs.
‘Intensive green roofs’ require the thickest soil layer suitable for growing trees and large shrubs. Intensive green roofs require a high-quality irrigation system that is used regularly to keep them green and lush all summer long.
‘Intensive roofs are not common because of their high cost and extreme weight. These types of roofs are generally found in luxury hotels, public buildings, museums and other large-scale constructions that require a strong visual impact.’
You may also see references to brown roofs. Biodiverse (brown) roofs are the most environmentally friendly option,” Ferris says. “They contain a variety of biodegradable and recycled materials, such as rubble, rubber and wood chips, to entice wildlife such as bees and small insects to live there.”
Heard about sedum roofing? Sedum has shallow roots and so only needs a thin layer of the growing medium. That is why it is a popular plant choice for an extensive green roof. Other benefits of Sedum include the fact that it is drought resistant, easy to care for and resistant to both pests and diseases.
What are the pros and cons of a green roof?
There are plenty of benefits to a green roof, but there are some potential drawbacks, and it’s worth knowing about both if you’re considering adding a green roof to your home.
- “The two main benefits of green roofs are temperature regulation (it keeps the building cool in the summer and helps keep it a little warmer in the winter) and rainwater retention,” says Gennaro Brooks-Church. ‘Sound insulation is also an advantage.’ Keep in mind that a cooler building reduces the need for air conditioning and can therefore lead to lower energy bills.
- “It reduces greenhouse gas emissions,” said Leonard Ang, CEO, lProperty management. How did this happen? A green roof absorbs carbon dioxide, the most abundant of the greenhouse gases, so you’re contributing to the efforts to fight climate change.
- A green roof can be installed on most horizontal and slightly sloping roof structures. Consider them for garden buildings, but also for additions and new homes.
- A well-designed green roof can mean a roof with a long lifespan. “If everything is done right, the green roof will extend or even double the life of the roof system by several years,” says landscape designer and garden expert Bryan McKenzie of Bumper trim times. ‘The green roof protects the main roof against UV rays, excessive moisture and too low temperatures. You can think of a green roof as a way to postpone roof replacement for another 10 to 20 years.’
- If you are building a new home or an addition to an existing home, go for a green roof and replace the ecology removed by your work.
- And while we’re putting this last, it’s certainly not the least. “Green roofs are aesthetically pleasing,” Orlando Ferris says. One of these is a great way to make your home and yard more attractive.
- “Green roofs are much more expensive than conventional roofs,” says Orlando Ferris.
- ‘In addition, they are heavy and use more material (stones, gravel). It can be very difficult for some buildings to bear the extra weight,” he adds.
- “Some may also argue about the limited choice of plants, as only those with non-invasive root systems are allowed,” says Bryan McKenzie. “I don’t agree with that, because there are too many plant species in this category and everyone can find what they are looking for.”
How much does a green roof cost?
Keep in mind that costs can vary widely. “Green roof projects start at $12,000 for small and medium extended designs, but the average project cost is $22,000,” says Bryan McKenzie. “Complex roofs that combine different zones can run up to $40,000 and beyond.”
In the UK, expect to pay around £50 per square meter for a sedum roof.