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To Green or Not to Green? Article on Green Roofs.

 Modern beautiful architecture is on the rise within the more vibrant sectors but with the recession still firmly in our lives and conscious new inner city buildings are not exactly popping up at a rapid pace. With this in mind for the most part, what buildings do we all have to enjoy today? How does your city scape look, beautiful and architecturally stunning or grey, drab and dull?
 
www.freeelectricitygenerator.co.uk

www.freeelectricitygenerator.co.uk

We may not be able to knock every grey Brutalist building down within some of the concrete jungles we live in, and some may even appreciate the grey backdrop to their workplace or residence but there are some retrofits that could help to make the environment we live in a greener and more pleasant one. I’m not out right knocking concrete, yes it is a useful versatile material but after the post-war construction drive to repopulate many of our cities what we are now left with 50-60 years on is a multitude of grey. One possible way to work with the stock we have is to retrofit the buildings with green roofs. This may be something which in new builds is often at least considered if not implemented but why not in the case of retrofits, the benefits are multiple.

For retrofits then intensive and simple intensive green roofs will pose a much greater problem in regards to structural stability of existing structures, whereas extensive design on the other hand presents a far greater opportunity in that the loadings are pretty much comparable to a standard flat roof construction. Extensive green roofs generally consist of a thin layer of soil, generally 100mm or less with relatively simple vegetation such as Sedum or Moss’s. Intensive green roofs have an increased level of depth, and hence more consideration is required in regards to structural support.
 green roof

www.worldchanging.com green roofs

 

Firstly let’s consider the technical and environmental impact of green roofs. Green roofs can be seen as one way to help with the global issue of climate change, however small an impact overall they may have, for global low impact buildings to become a reality every effort is needed no matter how insignificant it may appear in the wider context. One of the ways in which a green roof can help in this aspect is through increasing the thermal performance of a building. This is achieved through the green roof substrate and vegetation layer acting as a natural insulation barrier keeping unwanted heat during summer months whilst at the same time reducing heat loss during colder times.

As stated by CIRIA, Building Greener (2007), “Green roofs have a substantial thermal mass, a moderate insulation value and some cooling effect through evapotranspiration. These combined properties significantly reduce daily range of temperatures at the boundary between green roof and building structure” Making for a greater level of stability and comfort in regards to the internal environment.
goats on green roof

www.ecogeek.org goatsonroof

The vegetation that is provided through having a green roof can help increase the biodiversity of the surrounding context. By using a mix of vegetation, not only can the overall maintenance of the roof be reduced but the biodiversity can be increased. Now…I’m not suggesting that we should be farming goats on our urban green roofs as per the image to the left but you get the idea. To improve the biodiversity the simple step is to move away from the standard moss or sedum blanket and move closer towards the use wild-flowers which can be regional and hardy.  Wild-flowers will help to reduce the impact of higher winds whilst also enabling the roof to cohesively integrate with the natural wildlife which currently strives in the local habitats. 

 

Green roofs which include SUDS management can have further beneficial effects in terms of Carbon Sequestration and Storage (CSS). Looking at studies carried out by Getter and Rowe (2009), who carried out a study over the space of 2 years on 32 extensive green roofs in three US cities. The average CSS rates which they calculated was 0.375gC m-2. Through this research they calculated that if the city of Detroit were to install green roofs onto the 15,000ha of their rooftops then, “55 252 tons of carbon could be sequestered in the plants and substrates alone (not including avoided emissions). This is similar to removing more than 10 000 mid-sized SUV or trucks off the road for a year.”
 

Danny McGough green roof detail pdf

Danny McGough

As stated by Dr Charlesworth in (2010) a University lecturer specialising in SUDS, “Whilst there are many studies of the (CSS) abilities of certain SUDS devices, such as constructed wetlands, these would not necessarily be installed into urban centres. Green roofs, on the other hand, offer great potential both for new build and retrofit.” I will cover SUDS in greater detail within a later article as the details and benefits of specifying SUDS drainage are vast. So with all these benefits why don’t we paint the town in green roofs?
Retrofitting existing roof structures will obviously have a cost impact however if the roof needs repairing or upgrading regardless than obviously the impact of the costs is reduced. In a new development project  however the cost difference between specifying a green roof or not is far less or even non-existent in some cases. If we assess the green roof over the whole life instead of just the initial outlay then significant economic benefits can be seen.  As stated in Green Roofs – Benefits and cost implications (2004) “As whole life costing for new  development is emerging as an important tool for sustainability,  the fiscal benefits of a green roof during the life of a building after construction are likely to become more relevant.” Green roofs can also extend the life of a roof and reduce the service and maintenance that is normally required. This is achieved by the substrate and vegetation layer acting as a protection layer over the top of the roofing membranes, protecting them from UV light and frosts. Savings can additionally be made through the reduction of fuel costs through increasing the thermal performance of a building. This is achieved through the green roof acting as a natural insulation barrier reducing the variations in temperature within the building, keeping the building cool in the summer months and insulated further in the winter months. By reducing the heating and cooling load through the installation of this additional insulation layer, the demand on the energy required to heat and cool the building is thus reduced. With the targets for hitting carbon reductions looking tougher and tougher every small step that can be made is important to the overall grand scheme of things.

Moving beyond the technical jargon of the benefits of green roofs I also think it’s important to consider the social impact that a green roof can have on the people who inhabit the surrounding environment. With urban regeneration the focus can sometimes
be on creating more robust and versatile spaces rather than creating more visual and natural spaces.
 

www.greenroofstoday.co.uk  green rooftop

www.greenroofstoday.co.uk green-rooftop

A local space that I work near in Coventry has gone from this (1930’s):
www.bbc.co.uk  coventry broadgate 1930

www.bbc.co.uk

 


To this(1970’s): 

Sourced from- Google Images Coventry broadgate

Sourced from- Google Images

Sourced from- Google Images Coventry broadgate

Sourced from- Google Images

To This (2012);

www.newsrt.co.uk Coventry broadgate  new

www.newsrt.co.uk


Now, granted the vehicle traffic has been removed which  improves the robustness, versatility and openness to footfall fair enough, but could the planners not of kept some of the greenery? With us losing or have already lost plenty of green spaces  in our urban areas could green roofs be the answer to creating a more enjoyable and visually appealing urban environment, which in most cases is an urban grey cloud?

Information/opinions posted on this site are the personal views of the author and should not be relied upon by any person or any third party without first seeking further professional advice. Also, please scroll down and read the copyright notice at the end of the blog. 

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