What is Green Roof?

A new edited version is available here

As times goes on, more and more countries are urbanizing and this becomes a worldwide phenomenon. Cities are growing bigger in developed countries, and especially for developing countries with a huge number of population.

“(Cities) and the nature tried to coexist….but it wasn’t that easy.”

Trees and Animals are disappearing from our lives because of our violation to the environment. In order to replace the losing green environment, somebody come up an idea to plant vegetations on top of the buildings . This environmental technology is called the Green Roof.

The Green Roof is an environmental technology first founded in Germany in 1960s, and spread to other countries later. It covers the roof of a building with vegetation planted over a water-proof membrane with a design includes, as a minimum, a root repellent system, a drainage system, a filtering layer, a growing medium and plants.  The picture shows below layers of a typical green roof.

There are 2 types of Green roofs – intensive and extensive. Intensive green roofs can support a variety of plants and growth but are more labour-intensive. They are more park-like areas which may also be used as recreation space.

Intensive Green Roof

The extensive green roofs, in contrast, require less maintenance (about once a year) and are designed to be self-sustainable.

There are lots of benefits to have a green roof. It serves several purposes for a building, such as absorbing rainwater during peak rates in storm, lengthen the roof life 2 to 3 times potentially and negate acid rain effect. It also acts as an insulator of heat so that the demand of winter heat decreased. A new habitat is made for wildlife while reducing the amount of CO2 and toxin in the atmosphere. As a result, there is a reduction in city “heat island” effect and low the urban temperature, therefore reduces summer air conditioning costs.

The main disadvantage of green roof is its high initial cost. ($8 per square foot is a minimum amount which includes materials, work costs and installation whereas values around $12 to $24 per square foot are the most common, and may even cost more for the traditional built-up roofs)  Some green roofs have ongoing maintenance cost and thus enterprises may not want to put it in practice. Nowadays, there’s about 10% have been “greened” in Germany. (wikipedia) Besides Europe, green roofs are very popular in countries like United States, Canada, and Australia etc.

In Toronto, there’s a Eco-Roof incentive Program promoted by the City of Toronto to fund the green roof projects for industrial, commercial and institutional buildings. For more information, click the link below: http://www.toronto.ca/livegreen/greenbusiness_greenroofs_eco-roof.htm

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6 Responses to What is Green Roof?

  1. avatar Abayomi says:

    Sentence structure needs some work i.e. “number of population”. Nice summary of this topic. Would be interesting to see data on the actual effect of green roofs on climate change presently and the projected effect in the future. How do you see this topic developing into a project that you can do in a course? And if yes, what would form would it take?

  2. avatar jp says:

    Hi Adelina,


    Choice of topic:
    – Excellent. Very relevant.

    Use of resources:
    – The city of Toronto page referenced is a nice summary article about green roofs, but I think you can dig deeper to find more credible sources for information.
    – There are several statements of fact which are not supported by references to source material (e.g. “The Green Roof is an environmental technology first founded in Germany in 1960s”). Careful.

    Style / Coherence:
    – There are several grammatical errors in this post which make it harder to follow. I find it helpful to have someone else read over a draft to help pick up on them.
    – I felt your post ended abruptly. Consider a concluding paragraph that sums up what you’ve discussed.

    Understandability / Clarity:
    – Generally good. I think you could elaborate more on what a green roof is, the various types of green roofs, and in particular the difference between intensive and extensive — I was entirely sure I understood.

    Insights / Originality:
    – Good.

    Good use of blogging features:

  3. avatar Dustin says:

    wow, never knew these existed! they’re actually pretty cool, but after i read your post, i wonder whether they actually work or not? it really depends on the location to judge whether it’s sustainable/beneficial to the environment or not, because i’m from hong kong and in the summer, typhoons hit (less intense than tornadoes but more intense than incredibly heavy rainstorms). in bad weather, i guess destruction of the roof would just be an inappropriate use of money because the roof covers a large surface area and as you said, it’s quite expensive in the short-run. good topic though! quite interesting!

    • avatar Adelina says:

      Hi, Dustin. As far as I know, green-roofs are mostly hurricane-resistance which helps to absorb and slower the runoff of the rainwater. In cases of too strong typhoons, which trees even are blow-off in these scenarios, will destroy the roof. Therefore if the typhoon is not too strong, the green-roofs are able to withstand the hurricane-force wind. To minimize the destruction of the wind, the extensive green-roof, which remain less maintenance, can be considered to apply in large scale. By the way, I’m from Macau and I think the practice of green roofs can reduce the heat island effect.

  4. Pingback: What is Green Roof? (amended version) | PMU199 Course Blog

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