So what are the advantages to having a green roof?
A green roof can be classified as the addition of vegetation and soil to any roof type. Installing a green roof can actually reduce several negative effects that buildings would have on local ecosystems whilst simultaneously reducing the buildings’ energy consumption.
Living, or green, roofs
have been shown to increase sound insulation (Dunnett and Kingsbury 2004) and fire resistance (Köhler 2003). Because the vegetation dissipate solar radiation they can actually reduce the energy required for keeping the interior climates constant.
Hard surfaces can have a surprising impact on the wider environment. Predominantly, it is the role hard surfaces play in causing environmental problems that are the concern, with some of these problems being cumulative, therefore becoming more noticeable in the future. Flooding is the most significant of these problems. Potentially this can lead to flooding of homes, because hard landscaping can increase the amount of rainwater that runs off by as much as 50%. Street drains can’t always cope with the extra demand during a storm and can lead to damage and high repair costs. Green roofs can help to counter the effects through slowing down the volume of water flow from the roof, whilst also providing an opportunity for the water to be collected for use in the garden as and when required.
A green roof can provide an alternative recreation space either additionally to the space already provided by a garden, or if space is of a premium, instead of a garden.
The environmental benefits provided by green roofs derive from their functioning as ecosystems. They provide a habitat for wildlife in an area that perhaps otherwise would not have any suitable habitat. Additionally they could also be used as habitat corridors by some species who would otherwise not be able to cross such an open and unprotected space. In addition to these benefits there can also be an improvement in air-quality, and a reduction of the urban heat-island effect (Getter and Rowe 2006). For more information have a look at this link; green roofs as urban ecosystems.
An Example – Green Roof project in Scotland… When we were approached by the owner of The Coach House, Juliet, she mentioned that she wanted an environmentally friendly house, which also had an ‘appearance which fitted with the surroundings’, and, as she was having a roof built which could run into the field at the top of the garden, she believed that the green roof should be grass, instead of a pure Sedum mat.
This ecofriendly holiday house, The Coach House, Durhamhill, Dumfries & Galloway, as you can see from the photos above, does seamlessly blend into the surroundings. Below are a series of pictures which document the build and the installation of the Wildflower Roof Turf.
From what Juliet can recall, “it was difficult to get the building warrant as the Building Control people/our designer didn’t have documents to say how flammable it was. The designer then managed to persuade them that Sedum was Ok”.
“I later looked at the different types of natural roof available, and preferred your wildflower meadow to Sedum, so I ordered it”.
The design takes into account the field at the top of the site, so it made perfect sense for the architects to extend the green roof outwards in order to connect it to the adjacent field. This is a great example of taking into consideration the possibility of using habitat corridors, which in essence are small areas of vegetation which connect one habitat to another. Usually it is a habitat bridge or corridor connecting a garden or a section of garden to the larger landscape. This concept will go along way towards reducing the effect of habitat fragmentation
. Without the connectivity from the roof to the fields a potential barrier to many species would exist, meaning they otherwise would not be able to cross this gap.
So the next step is to get the substrate on the roof ready for the turf to be installed… As the pictures below illustrate the chosen method for this project was to use our non-degradable substrate sacks around the perimeter of the roof, which will add stability whilst forming a nice neat edge. Once the sacks have been placed on the roof the next step is to back-fill the remaining area with our loose substrate. As you can imagine without machinery this would be a labour intensive task!
The next stage is to rake out the loose substrate making it nice and even and smooth. We recommend a depth of 100mm, so our sacks would have been supplied at 100mm depth making it easy to level the loose substrate to the same depth as the sacks. Some contractors like to have a little extra loose substrate to screed the sacks, filling in the gaps, however this is not vital. And guess what? There was enough substrate and turf after all!
Pictured below illustrates how easy the turf is to handle. It unrolls like a carpet. Each roll needs to be butted up to the next one, but make sure they are not overlapping each other. This should ensure no weeds can grow through any gaps.