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What Are The Key Benefits of a Green Roof?

How Does The Appliance of Science Deliver Green Roof Success

Improving the Environment

Carbon sequestration
Plants absorb carbon dioxide and release oxygen during photosynthesis thereby counteracting emissions and help towards net zero.
Air quality. Sedum and other green roof plants absorb soot and other pollutant particles which helps to improve air quality.

Urban Heat Island Effect
The evaporative cooling of green roof vegetation also reverses the heat reflecting effect from hard impermeable surfaces such as waterproofing membranes and concrete. The plants actually absorb heat and turn that heat into energy to grow, unlike concrete or brock which will absorb heat during the day and radiate it back into the atmosphere, artificially increasing the ambient air temperature.

Micro Biodiversity
Green roofs can replace and create habitats that have been lost as a result of urban development and replicating what was at ground level to roof level; encouraging a range of insects, birds and other wildlife.

Macro Biodiversity
Green roofs can be used to allow the creation of ‘green bridges’ or ‘bee corridors’ through the built environment. This not only helps with the aesthetics of the area but also allows the natural flow of flora and fauna through urban developments.

Acoustic performance
An extensive Green Roof can insulate up to 40dB and an intensive Green Roof can insulate up to 50dB. This reduction in transfer of noise can make a noticeable difference in highly dense urban environments.

Improving the building

Protecting the waterproofing
The build-up of a green roof protects the waterproofing layer by covering it. This reduces the impact to the membrane from UV, temperature fluctuations and other atmospheric pressures. A green roof protects the waterproofing by mitigating expansion and contraction. This protection prolongs the life of the waterproofing.

Reduction in solar gain
Returning moisture to the atmosphere through evapotranspiration, solar gain can be reduced. Moist air helps trap dust and some gasses which reduces pollution

Amenity and well-being
Green roofs have a positive visual impact and can provide valuable outdoor recreational areas.

Creates more space
A green roof can create an amenity or leisure space for the building which maximises the footprint and gives greater financial yield. Green roofs can include playgrounds and play areas, ornamental gardens or areas in which fruit and vegetables can grow. They have been shown to improve people’s mental health.

Building performance

Insulation
The evaporative cooling effect combined with increased insulation or thermal mass can reduce the need for summer cooling (air conditioning etc) which results in reduced carbon emissions.

Scoring BREEAM points
Improving the energy performance of buildings and embracing Green Roofs helps to meet standards such as the code for sustainable homes and BREEAM. It also helps to meet planning requirements and revisions in Part L Building Regulations.

A development incorporating a Green Roof can earn up to 6.2 points on an Eco Homes score. It can also score substantial points for sections LE04 and LE05 using the ecology of the roof to enhance plant species, local biodiversity and water storage.

Aiding planning consent
There are a number of central and local Government initiatives (including the London Plan) to encourage the greening up of both existing spaces and new build developments and often planning consent is directly tied to green roofs and sustainable drainage systems.

Reduces whole life costs
Typical roof installations have a life expectancy in the region of between 15 and 20 years. The building of a green roof system has been shown to have a life expectancy in excess of 50 years. This means the whole life of the development will be significantly lower than a traditional roof construction.

Drainage

Water attenuation and flash flooding
Urbanisation and land development creates hard impervious surfaces, which absorb only 5% of rainfall. The remaining 95% of the rainfall becomes run off. This puts enormous strain on sewers and river systems. Adding a green roof can capture over 50% of rainfall and will slow down the time before the run-off rainwater hits the drains for up to 1 hour. This is a major benefit in reducing the risk of flooding.

Green roofs as part of a SUDs solution
Sustainable drainage and water retention and attenuation are major parts of the SUDs design and method. As well as capturing stormwater and slowing the run-off, green also provide a filtering and cleansing benefit.

Water discharged from a green roof is proven to be cleaner than from concrete surfaces and this water can be stored and recycled within the building / masterplan development via grey water schemes.

For more information, please click here.

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Can Exterior Green Walls Contribute to a Carbon Neutral Architecture?

An image of a green roof installation at the Radisson Blu Hotel, Heathrow

A carbon neutral building is achieved when the amount of CO2 emissions is balanced by climate-positive initiatives so that the net carbon footprint over time is zero. Considering their unmatched ability to absorb CO2, planting trees is often viewed as the best carbon offsetting solution. But as cities become denser and the amount of available horizontal space for green areas drastically reduces, architects have been forced to explore other approaches. Therefore, to address these climatic challenges and connect people to nature, exterior green walls have become a rising trend in increasingly vertical cities. Even if there is research to claim that these can positively impact the environment, many question if they can actually contribute to a carbon neutral architecture. Although the answer may be quite complex, there seems to be a consensus: green walls can be effective, but only through good design.

Surprisingly, green walls are a relatively new concept; in fact, the idea was first popularized by French botanist Patrick Blanc in the 1980’s. Hence, this might explain why the design community still hasn’t reached a consensus on their environmental role. Nonetheless, to get a deeper insight on the current debate, below we explore their potential benefits, challenges and critiques from a sustainability standpoint – as well as design decisions that could contribute to more climate-friendly solutions.

flowering sedum close up spring

What is a green wall?

A green wall is a vertical structure covered with vegetation. Essentially, a living cladding system. Instead of being adorned with climbing plants rooted from the ground like in traditional green facades, these provide a vertical growing surface in the form of modular panels, tray systems or freestanding walls. The greenery is planted in a growing medium, such as packed soil, fiber mats or other substrates, and features an integrated irrigation system.

Environmental advantages associated to exterior green walls  

Of course, an evident benefit of these eye-catching pieces is their biophilic effects and the visual aesthetic value they add to cities, making them greener and nicer places to live in. However, green walls are also linked to sustainability benefits. By using vertical areas that are abundant in cities, they are viewed as a way of maximizing CO2-absorbing greenery without sacrificing valuable ground space. While a tree absorbs around 5.5 kg of CO2 a year, it is claimed that 1 m2 of green wall can absorb up to 2 kg, also improving air quality by eliminating harmful toxins.

Please visit the Arch Daily website for the full article by clicking here.

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How To Maintain Green Roofs

Fertiliser added to a green roof

Green roofs are living structures and as such need attention throughout their lifespan. Some vegetation types such a sedum are planted as they require less maintenance than grass roofs for example. However, regular attention to soil moisture and feed levels as well as the removal of weeds is essential to maintain optimum performance.

Extensive green roofs including M-Tray® modular roofs

Spring schedule

  • Remove weeds by hand pulling only
  • Apply Wallbarn slow release granular fertiliser at a rate of 50gsm
  • Clear debris from drainage outlets
  • Generally inspect vegetation area and monitor poor growth areas
  • Insert cuttings from good growth areas into bad growth areas
  • Check irrigation system (if applicable) and replace timer batteries

Autumn schedule

  • Remove weeds by hand pulling only
  • Clear debris from drainage outlets
  • Generally inspect vegetation area and monitor poor growth areas
  • Cut back dead stalks or dying vegetation
  • Insert cuttings from good growth areas into bad growth areas
  • Check irrigation system (if applicable) and drain down

General points

Sedum

Sedum is a unique plant in that its metabolism is reversed from most other plants. Sedum closes its stamen during the day which contributes to it being more efficient at conserving water. Sedum leaves will change their colour at times throughout the year and will often take on a russet colour during, drought, strong wind and frost. This is normal and they will revert to their normal green hue over time. Should the stems and leaves start to ‘shrivel’ back then this is a sign of a problem and in the main lack of water. Irrigation must be applied to reverse this and the levels of water checked for several weeks until the sedum has recovered.

Wildflowers

Wildflowers are weeds and weeds are wildflowers and so care must be taken during maintenance NOT to pull out healthy and desired plants. Wildflowers by their nature thrive on poor soils where there is little competition however they are more vulnerable to drought. Drying of stems and leaves will be seen through hot dry periods and although irrigation can be applied it is not a requirement as the ‘stressed’ plants will flower.

For more information, please click here. 

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When Should You Maintain Your Green Roof

Close Up of Wildflower M-Tray on Roof of Turing House

Green roofs are living structures and as such need attention throughout their lifespan. Some vegetation types such a sedum are planted as they require less maintenance than grass roofs for example. However, regular attention to soil moisture and feed levels as well as the removal of weeds is essential to maintain optimum performance.

Extensive green roofs including M-Tray® modular roofs

Spring Schedule

  • Remove weeds by hand pulling only
  • Apply Wallbarn slow-release granular fertiliser at a rate of 50gsm
  • Clear debris from drainage outlets
  • Generally, inspect vegetation areas and monitor poor growth areas
  • Insert cuttings from good growth areas into bad growth areas
  • Check the irrigation system (if applicable) and replace the timer batteries

Autumn schedule

  • Remove weeds by hand pulling only
  • Clear debris from drainage outlets
  • Generally, inspect vegetation areas and monitor poor growth areas
  • Cut back dead stalks or dying vegetation
  • Insert cuttings from good growth areas into bad growth areas
  • Check the irrigation system (if applicable) and drain down

General points

Sedum

Sedum is a unique plant in that its metabolism is reversed from most other plants. Sedum closes its stamen during the day which contributes to it being more efficient at conserving water. Sedum leaves will change their colour at times throughout the year and will often take on a russet colour during, drought, strong wind and frost. This is normal and they will revert to their normal green hue over time. Should the stems and leaves start to ‘shrivel’ back then this is a sign of a problem and in the main lack of water. Irrigation must be applied to reverse this and the levels of water checked for several weeks until the sedum has recovered.

Wildflowers

Wildflowers are weeds and weeds are wildflowers and so care must be taken during maintenance NOT to pull out healthy and desired plants. Wildflowers by their nature thrive on poor soils where there is little competition however they are more vulnerable to drought. Drying of stems and leaves will be seen through hot dry periods and although irrigation can be applied it is not a requirement as the ‘stressed’ plants will flower

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5 benefits offered by installing green walls

View of green roof installed at Kew Green

Homeowners who don’t have a lot of space outdoors can bring plant life indoors and reap the benefits of having green walls, also known as vertical gardens or living walls, in their homes. If you’re considering installing a green wall in your home but you aren’t sure if you’re ready to commit, here are five benefits of having a green wall in your home. 

Improved air quality

There are a lot of pollutants floating around in the air and we all know that plants are Mother Nature’s air filters, so why wouldn’t we want them in our homes? People who live in areas where the air quality isn’t the greatest can certainly benefit from installing a green wall in their homes, but they aren’t the only ones. Not only do plants purify outdoor pollutants, but they also help remove things like cleaning chemicals, burnt food, and the gas from appliances from the air. 

Health and well-being

Our surroundings have an impact on our mental health and overall well-being, so it should be no surprise that many people turn to nature to center themselves. Green walls are a great addition for anyone who’s stressed out, needs a boost in productivity or creativity, and just feels better. Also, since plants produce oxygen, just imagine how much better you’ll feel when you have your own source of pure oxygen!

Aesthetics

Decorating your home doesn’t have to mean you’re filling the space with trinkets, odds, and ends! Green walls act as a statement piece – the eye-catching feature that makes the space stand out. It’s worth noting that homes with this feature are sure to appeal to the eco-conscious buyer and is sure to help your home sell.

Temperature and noise control

Green walls can reduce the temperature and noise level of a small space because the plants absorb and reflect energy. The plants create shade, therefore helping to reduce the temperature inside the room. That means you’ll have better control over the temperature and, consequently, your energy consumption. 

Urban farming

Homeowners who have space outdoors can create a green wall outside and it’ll be a source of pollen and nectar for birds, bees, and other animals. Inside, you can create a vertical garden and have fresh herbs, fruit, and vegetables. So, not only will you have cleaner air, improved health and mental well-being, and a beautiful space… You’ll have fresh produce, thus cutting down on your grocery bill! 

When someone talks about having a green wall in their home, they’re probably not talking about the wall being painted green (although that is a possibility, of course). They’re talking about a living wall full of greenery! 

It may seem like having a green wall in your home is the latest design trend, but it’s more than just that. They can improve so many aspects of our lives and give us a sense that we’re doing something good for ourselves and the environment. Granted, one or two green walls in a home aren’t going to change the world, but it’s a start.

For the full article, please click here.

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Green roofs are being added to 30 bus stops in Singapore

M-Tray® - Turing House school project

In recent years, you might have noticed grass growing on the roofs of a select few bus stops in Singapore.

The project, ongoing since 2019, is a collaboration between the Land Transport Authority (LTA) and the National Parks Board (NParks).

Cools the area

The green roofs aim to reduce ambient heat and provide a more comfortable experience for commuters, a LTA spokesperson told Mothership.

Preliminary studies show that these green roofs can lower ambient temperatures at the bus stops by around 2°C.

“Skyrise greenery, such as vertical green walls, green roofs, and rooftop gardens will cool the buildings and make them more comfortable to live, work and play in, while further beautifying our city,” Oh Cheow Sheng, group director of streetscape at NParks, told Mothership.

As part of this initiative, green roofs will be installed at 150 bus stops.

These comprise new bus stops as well as those slated for upgrading under LTA’s Bus Stop Infrastructure Enhancement Programme.

30 bus stops fitted with green roofs

Around 30 bus stops have been fitted with green roofs as of July this year.

These include bus stops in Jalan Bukit Merah opposite Block 28, along Henderson Road opposite Block 55, and along Ang Mo Kio Avenue 1 at Block 248.

The remaining will be progressively deployed over the next two years.

Oh said NParks provided expertise on the plant species used in the project and the design of the green roof for ease of maintenance.

The plant atop the bus stop is a species of herb known as Nabhali (Cyanotis cristata), which was selected for its hardiness and ability to grow and spread well on green roofs.

According to NParks, it is drought tolerant and able to withstand at least two weeks without rain or watering.

For the full article, please click here.

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Green roofs can provide a boost to energy efficiency and benefit the environment

M-Tray® - Turing House school project

Green roofs can save people money on energy bills and benefit the environment at the same time, according to property management company FirstPort.

Also known as a living roof, you can make a green roof by partially or fully covering the top of a building with self-sustaining vegetation, such as moss, grass, sedum or small flowers.

Usually found on large residential developments in cities, they can promote wildlife, boost the environment and minimise carbon emissions.

According to FirstPort’s Sustainability manager, Christian Phipps, green roofs are also a great source of insulation which could help to combat the cost of living crisis: ‘Green roofs are not only good for the winter by offering an extra layer of insulation to keep heat in a building but conversely, they can also cool buildings in the summer and reduce urban heat islands.

‘Plants also naturally absorb harmful pollutants, which some studies have linked to some 40,000 early deaths in the UK a year, so there’s clearly health benefits too. And if green roofs can also help to reduce the cost of living in any way, then it’s a win-win.

‘We want and will be looking to create more green roofs, or even green walls which are better for air purification and cooling at a ground level.’

FirstPort have already put this measure into practice on one development, Greenland Place in Lewisham with 700 apartments, workspace, retail space and a self-sustaining green roof terrace.

Development Manager George Proctor believes the space is beneficial to mental health and sees it as an effective measure for warming the building.

He said: ‘It reinsulates the building and gives you another six inches of insulation material, so it keeps the heat in the building. There are so many benefits, and it is so low maintenance.’

In related news, a report by the Environmental Audit Committee (EAC) has warned the government must reduce carbon emissions in the construction industry if net zero targets are to be met.

For the full article, please click here.

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What can Rotterdam teach about the power of green roofs

M-Tray® - Turing House school project

From May 26 to June 26, the Dutch city of Rotterdam is showcasing the potential of rooftops. The Rotterdam Rooftop Walk connects rooftops through air bridges, offering a vision of the future of cities.

“Often, cities offer little space to develop more green spaces, and rooftops provide that space for plants and for biodiversity,” says Léon van Geest, director of the Rotterdam Dakendagen Festival.

Green rooftops can be an effective solution to urban heat islands, cities or specific neighbourhoods within an urban area that have become much warmer than their surroundings due to absorbing and re-emitting the sun’s heat. Disenfranchised urban areas are particularly struggling with heat: A 2021 study in the Nature Communications journal found that heat exposure tends to be higher in lower-income neighborhoods, both in the U.S. and globally. Residents of these neighborhoods are also less likely to have air conditioning, or may be unable to afford to use it even if they do have it. This heat exposure aggravates inequality through risks such as higher heat-related mortality, heat strokes, dehydration, loss of labor productivity and decreased learning capacities, while also increasing costs for air-conditioning.

Enter green rooftops. They can take many shapes — lush gardens, potted plants, solar panels, urban farms, wildflower meadows and community spaces painted in light colors that absorb less sunlight — and can help combat heat islands in several ways. Plants and even trees on the roofs of buildings can drastically lower the urban heat island effect by reducing temperatures. According to the EPA, citywide ambient temperatures can be lowered by 5 degrees Fahrenheit with green roofs, reducing building energy use by up to 0.7 percent and thus lowering energy demand. Green roofs can also retain water and thereby prevent or reduce urban flooding. They filter greenhouse gas emissions and other pollutants from the air and attract more biodiversity.

Please click here for the full article.

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Time to join the green roofing revolution?

Green Roof on bus shelter

Green roofs are an aspirational choice for many self-builders and home renovators wishing to finish their project with a gorgeous living roof that changes with the seasons and attracts a host of insects and birds.

Demand for green roofs is booming, with many manufacturers – Wallbarn included – reporting their strongest sales to date in 2021. It’s a green revolution driven by consumer commitment to sustainability and a desire for more natural products and a more natural finish.

The benefits of green roofs are well-documented but we find that most homeowners are interested in two key areas – the ‘feel good factor’ of having a living roof and their ability to support biodiversity, creating habitats for flora and fauna (most notably pollinators; a study of green roofs in London recorded more than 20 species of bee foraging on them).

In addition, they are a valuable asset in managing storm water run-off by extending the time between rain falling and entering the drainage system and have been proven to improve air quality by absorbing pollution and dust particles (up to 0.2kg per m2). In towns and cities they reduce the Urban Heat Island effect by absorbing heat rather than radiating it back into the atmosphere and offer sound and thermal insulation benefits. There’s also evidence that adding a green roof helps with gaining planning permission, can make a building sell more quickly and add value.

With so many benefits it’s easy to understand why green roofs are so popular. And product development means that you now have a greater choice of how your roof looks. Sedum has long been the go-to plant of choice but some producers are offering British wildflower mixes which deliver an even more natural finish with greater seasonal variation in appearance.

For those considering including a living roof in their plans there are two key considerations:

  • Load bearing ability of the building
  • Choosing a traditional roll-out green roof or modular system

Load bearing

This is the first consideration for any green roof, modular or roll-out. A structural engineer should advise if the structure can support the weight. For new-build projects or extensions the required structural integrity can be designed in.

Traditional or modular?

Until a few years ago the established method for laying a green roof involved installing each element separately, so drainage, root barrier, substrate and sedum plants. For large expanses or roofs with different depths or a pitch higher than around 15° (for example a convex design) this traditional approach remains popular.

The alternative is modular systems which combine all elements of a green roof, including plants, in pre-prepared trays that click together. They are, essentially, a green roof in a box and deliver an instant finish quickly and cleanly with little on-site waste. Quality control is high because all elements of the system are prepared off-site in a controlled ‘factory’ setting, ensuring optimum plant health and long-term growth. The best systems are ‘grown on’ for at least nine months and quality checked before dispatch, ensuring a fully established green roof with mature, well-rooted plants arrives on site. Specification is straight-forward and investment in the product recouped from on-site time and labour savings.

Modular solutions offer three distinct advantages:

  • Competent self-builders and renovators can install them; just lay the supplied geotextile fabric onto the roof membrane/finish and position the green roofing cassettes, clicking them into place. It’s a one-stop-shop solution that’s clean, quick and straight-for
  • Where site access is an issue modular trays can be carried by hand through buildings, upstairs and passed through windows to reach inaccessible roofs, all without mess or disruption.
  • If access is required to the roof deck post-installation it is straight-forward to remove and re-install individual trays.

Technical considerations

For both traditional and modular green roofs there are important technical considerations. Fire regulations require a hard border between vegetation and building walls and around features such as rooflights. The roof also needs to be relatively level and generally no more than a 15° pitch.

Fire performance

This is an area being more frequently discussed in relation to green roofs. Leading manufacturers offer systems with industry fire classification proof (T4) EXAP gained through physical independent testing to CEN/TS1187:2012 (Test 4) and CEN/TS 16459:2019, Test methods for external fire exposure to roofs. Look out for no fire penetration of the green roof system in a one hour physical fire test and ask for certificates.

Substrate

Not all green roofing systems offer comparable substrate depths (substrate is the growing medium for the plants). The GRO Green Roof Code (www.greenrooforganisation.org) lays out recommended minimum depths for different systems, starting from 60mm. We believe that 100mm is the ideal depth for modular systems, allowing optimum space for healthy roots. The Green Roof Code also discusses the content of substrates and advises that they should comply to BS8616:2019 Specification for performance parameters and test methods for green roof substrates. An independent laboratory test showing that the substrate complies to BS8616 should be provided by the roof supplier.

Delivery

With any green roof system it is important to consider time spent in transit and the need to unpack the system within 24 hours of delivery to ensure optimum plant health. If left too long on transport crates – we advise a maximum of 48 hours – enzymes begin to break down the plants.

Maintenance

Green roofs are low maintenance but not no maintenance. Sedum plants are hardy and will tolerate extreme conditions – there are green roofs worldwide thriving in a wide variety of climactic conditions, some of them 75 years old or more. In exceptionally dry conditions it may be necessary to water the roof; some clients choose to install an irrigation system and we recommend twice yearly maintenance including applying a slow release fertiliser for best year-round results.