Everything you need to know about Green Roofing systems.

Vancouver Convention Centre Green Roof

While working on a roofing project recently I realized the concrete jungle we are surrounded by. The sea of asphalt, black tar and gravel-ballasted rooftops got me thinking about eco-friendly rooftops, known as the green roofs. However, there is still a stigma in people about adopting this roofing system. This article addressed everything you as a homeowner or business owner need to know about green roofs.

Keep reading to know more…!

What Do You Mean by Green Roofs?

In simple words, green roofs are dynamic roofing systems designed to accommodate the growth of small plants on top of a roof. Experts also define it as, “A layer of vegetation planted over a waterproofing system that is installed on top of a flat or slightly–sloped roof.” A Green roof system consists of many different layers. However, some of the common layers in all types of green roofs are Vegetation and growth medium, filter membrane, drainage layers, waterproofing/ root replants and roofing membrane support.

History of Green Roofs.

Hanging Gardens of Babylon

Did you know the birthplace of the modern-day green roof system is in Germany? However, the popular concept of green roofing dates back to 500 B.C. Babylon. Back then the most famous green roofs were the Hanging Gardens of Babylon, which were referred to as the seventh wonder of the ancient world. These were built over arched stoned roofs, and layers of thick tar and reeds were used for waterproofing. With the technological advancements after the second world war, more importance was given to sustainable development. In the 1960s the concept of green roofing resurfaced in Germany. However, this time a more modern and practical approach was taken. A layering system was used to make the green roofs durable. Today several countries in the world have adopted green rooftops over traditional roofs. Beautiful green roofs can be seen in countries like America, Canada and some Asian and European countries.

Types Of Green Roofs.

Green roofing systems can be differentiated based on two major factors. The amount of vegetation it can hold per square foot and the level of maintenance it may need.

There are three types of green roofs: Extensive, Intensive and Semi-intensive.

3 Types of Green Roofs

Extensive Green Roofs.

These roofs are designed to have naturally low maintenance. They offer the environmental
benefit we seek by constructing a green roof, but nothing else. They can hold from 60 to 150
kg of vegetation per square meter. Extensive green roofs are best for large flat-roof
buildings, apartments and low-sloped residential roofs. These roofs consist of desert grass
and succulent plants. They need minimum water and after a year they do not need watering
at all, just an annual wedding.

If you are looking for a sustainable green roofing system that requires minimum labour,
extensive green roofs are for you!

Intensive green roofs

Intensive roofs as their name suggests, need a lot of care and labour to maintain. These
roofs can hold from 150 to 500 kgs of vegetation per square meter. If you are seeking floral
diversity in your green roof you should go for an intensive green rooftop as it allows herbs,
shrubs, plants and even trees on it. Having an intensive green roof is equal to having an
actual garden.

If you choose to have these roofs you need to look after the plants growing, separate them
from one another, regular watering, fertilization and eliminate the weeds. Generally, private
homeowners pick this type of green roof. As they have the freedom to choose the plants
they wish to grow and design the aesthetics of the roof.

Semi-Intensive Green Roofs.

Semi-Intensive is a sweet center between intensive and extensive green roofs. These roofs
can hold from 120 to 250 kgs of vegetation per square meter. They were invented to
accommodate a variety of plants and a limited
Pros and Cons of Green Roofing systems.
Pros of having Green Roofs.
Green roofs offer more benefits than you think. These are the reasons why you should get a
green roof and some of them are mentioned below.

Automatic Rain Water Management.

If you live in a region where the climate is unpredictable, a green roof can be a great
advantage. As it absorbs a majority of rain/ stormwater. This reduces your effort in managing
the accumulated water. Plus, it lowers the stress of the sewer system.

Better heat insulation

Just as it absorbs rainwater it also reduces the heat conductance of the building. As its
multiple layers keep the inner temperature constant.

Increases the Overall Lifespan of the Roof.

The roof has to cope with a lot of damage throughout the years. Its lifespan greatly depends
upon its exposure to the elements and regular roof maintenance.

Green roofs prevent these elements from directly interacting with the waterproof membrane
of the roof. Reducing the damage caused otherwise. This increases sustainability and adds
years to the lifespan of your roof. A green roof can last up to decades with proper
maintenance and care.

Helps the environment.

One of the most obvious reasons to install a green roof system is to support the
environment. Especially in urban cities, where almost 44% of total CO2 emissions are
released from buildings, green roofs are a great option to curb this excess emission.
Installing green roofs in cities and urban regions is one of the best solutions to increasing
global warming.

Offers Wildlife Support.

While we cut down forests to fulfil our needs, a green roof on houses or other buildings is a
great way to help wildlife thrive. Green roofs can never replace actual grounds. However, it
can still be a great place for birds and other tiny creatures to start a new life.

Depending upon the vegetation on the green roofs different species can coexist. In a study
carried out in Switzerland, 11 rooftops with varied vegetation were surveyed. They were
inhabited by 172 species.

Refined Air.

With a large number of people and animals facing the backlashes of breathing polluted air
annually, green roofs are one step towards natural air purification in metropolitan cities.
A study proves that green roofs reduce up to 37% of sulphur dioxide, 21% of nitrous acid
and 0.2kg of dust particles / square meter each year.


Green Roof architecture is not just better for the environment but is extremely pleasing to
look at. Green roofs not only increase the aesthetic appeal of the structure but also increase
the market value of the structure.

ACROS (Asian Crossroads Over the Sea) Fukuoka Prefectural International Hall at Tenjin Central Park, Fukuoka, Japan

Cons of having a Green Roof.

Along with their benefits green rooftops come with a few disadvantages too.

A Green Roof Life Style Requires Your Time and Attention

It’s Expensive.

It’s no news that such a multipurpose roof is costly. A green roof costs more than a
traditional roof. The primary reason is the additional support it needs to hold up the weight of
so many layers plus the plants.

However, this initial investment is paid off in the future years, as this roof is more durable
than a traditional roof. So, the cost of roof replacement or maintenance is less. It can be
further reduced by installing an extensive green roof.

Heavy Roof.

The multiple layers of a green roof make it heavier than an ordinary roof. This increased roof
weight needs structural modifications to support it. Most of the flat roofs fulfil the
requirements needed to install a green roof. However, some roofs may need retrofitting to
support a green roof system.

Normally, the weight of a green roof per square meter ranges from 50 kgs to 250 kgs. In the
case of the intensive green roof, it may go as high as 500kgs per square meter.

Needs Maintenance.

Just like any other rooftop, green rooftops need regular maintenance too. Maintenance can
be a hassle if you have an intensive green roof. However, extensive or semi-intensive green
roofs need little to almost no maintenance after a while.

Greens Roofs need Insurance.

All sorts of roofs need insurance to recover from unforeseeable damage. However, the
insurance of green roofs is slightly more expensive than others. Due to its layering and
vegetation, the cost of restoring a green roof is high and so is its insurance.

Cost Estimation of a Green Roofing System.

A big part of installing and maintaining a green roof is its cost. Now, if you are looking
forward to replacing your existing roof with a green roof or installing a brand-new green roof.
Here is an average cost estimation of a green roofing system.

Depending upon the type of green roof you install the average cost of any green roof ranges
between $10 to $30 per square meter.

This cost may increase or decrease depending upon whether you are planning to install an
intensive roof with exotic plants, which are planted systemically. Or you prefer an extensive
roof where the vegetation can be grown with the help of a vegetation mat and other
environmental factors.

Although, the plants and materials you need for green roof construction are readily available.
The cost of transportation adds to the overall cost.

Moreover, while setting a budget for your green roof, it’s most important to consider the cost
of future maintenance. Depending upon the type of green roof you choose. The size of your
roof and the insurance cost. All these factors together will contribute to your overall
expenditure on a green roofing system.

Additional Things You Need to Know Before Getting a
Green Roof.

Whilst the advantages and disadvantages speak for themselves, here are a few more things
you need to take into consideration before investing in Green Roof Systems.

Must Follow the Proper Installation Process

Design Matters.

The life span, performance and looks of a house with a green rooftop depends on its design.
There are plenty of designs of green roofs, however, you need to choose the one that
benefits you the most depending you’re your climate and surroundings.

Pick a design that causes minimum to no wind uplift. If there is too much air pressure
trapped underneath the green roof when the wind blows overhead, it may cause a pressure
shift, pulling the greenery off the roof.

Installation process.

I would highly recommend you hire a skilled contractor to install your green roof. As the
installation process is intricate. If you try to do it yourself without any prior experience you
may end up damaging your roof.

Roots of the plants.

The roots of vegetation on top of your green roof may interfere with the structure of your
building. To keep the roots from compromising the roofing layers below and the structure of
the building, precautions need to be taken.

How Do I Know If I Should Get a Green Roof or Not?

If you are thinking about getting a green roof, you need to have a word with certain
professional individuals.

Firstly, seek a structural engineer to inspect the structure of your property. He/ she will let
you know if your property is capable of supporting a green roof. In not what are the steps
you need to take to get off the additional support a green roof needs? Also, he/she will let
you know what precautions to take while you are setting up a green roof.

Next, connect with a good roofing contractor known for completing green roof projects and
get a quote. This will paint a clear picture for you. Also, consulting a roofing contractor will
help you know whether you should get a green roof or not. Depending upon your location,
climate, nature of your property, it’s surrounding, etc. a professional contractor will be able to
guide you much better.

If you happen to live in B.C. then you have the team of the best roofing contractors at your
service. Blackwater Roofing has completed multiple green roof jobs. Right from complete
roof installation to minor repairs and maintenance. Blackwater Roofing does it all!


I hope this article answers all your questions regarding green roof construction and
maintenance. If you have any further questions or need a quote for any roofing service,
comment down below or visit our website.







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