Green roof report1


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DT117/4 Sustainable Build & Design - Class Presentations

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Green roof report1

  1. 1. David O Dowd Green Roofs Student Name: David O’ Dowd Student Number: C06550410 Subject: Sustainability Project Title: Green Roofs Lecturer: Sonya Daly 1
  2. 2. David O Dowd Green Roofs Table of Contents Definition of the term Green Roofs The reasons for using Green roofs The three main types of Green roof Construction methods for Extensive Green Roofs Familiar examples of Green roofs References 2
  3. 3. David O Dowd Green Roofs Definition of the term Green Roofs There are various definitions applied to the term “green roofs” but in its simplest terms a green roof can be defined as: A structure which has a covering of some form of organic material as a roof cover. This material can range from moss or turf up to trees depending on the building it is going to be applied to. The reasons for using Green roofs There are quite a few reasons to use green roofs in construction. It has many direct benefits and indirect benefits to the owner of the building and indeed the environment. One of the benefits to the employer is that the costs of heating and cooling the building will be reduced. This is because green roofs provide a very high level in insulation so they keep the heat in during the winter and the heat out during the summer. This factor is quite important as a study in the U.K has found that building owners spend more “money cooling buildings in the summer than they do in heating them in the winter.” (Erik van Lennep 2008). Green roofs have proven the ability to retain 60% - 100% rain fall. Usually it is closer to the 60% region. This reduces the pressure exerted on the public drainage systems. This is a benefit to the environment as usually in cities rainfall lands on impermeable surfaces and so there is no absorption and the run-off flows directly into the drainage systems and this can cause the systems to overflow. This also affects the quality of water. As with all plants and trees they absorb Co2. These emissions given off by cars and houses and are soaked up by plants. By having green roofs in cities this will reduce the amount of Co2 being emitted into the atmosphere. The amount of Co2 that is absorbed per green roof is relatively small but with a large amount of green roofs it can make a difference. Temperatures within cities are usually higher than in the countryside. This is down to the heat given off by traffic, roads and buildings. This effect is known as “urban heat island” cited by Santamouris 2001 in Erik van Lennep report. The introduction of green roofs would reduce the temperature in towns by a few degrees Celsius. Other benefits which will not be discussed in the presentation are that green roofs can last twice as long as traditional roofs. They also improve quality of air, water and provide the basis for amenities. 3
  4. 4. David O Dowd Green Roofs The three main types of Green roof The first type of green roof is an intensive green roof. This type of green roof does not usually have a maximum soil or substrate depth. There is also no restriction on the number of trees or plants that can be used on this. It is most likely to be found at ground level or the top of apartment blocks. These green roofs may even appear like a park with paths, grass benches and even playgrounds. Regular maintenance is required so ease of access is necessary. This type of green roof is the most expensive. One example of this green roof is in Fukuoka city in Japan where one building has 75,000 plants with over 70 different species. The second type is a semi-intensive green roof. Due to the substrate layer being restricted to a certain depth this means that this type of roof is restricted to smaller shrubs and plants. This is not intended for a recreational area but reasonably easy access is still required for maintenance purposes. This type of green roof is less expansive than the previous type. An example of a semi-intensive green roof is the roof covering on the Airport in Amsterdam. The final type of green roof is an extensive roof. This means that the roof is restricted to small organisms such as grass, turf and moss. This is due to the fact that the substrate layer can be as little as 15mm. This type of green roof is light weight, cheap and requires very little maintenance. These characteristics make the most applicable solution to domestic dwellings. Maintenance is little as once or twice a year. The construction is relatively easy. Construction methods for Extensive Green Roofs As extensive green roofs are the most applicable to the domestic market. I shall go into detail as to how and go about constructing a green roof. The roof is constructed normally until the rafters have been erected. Then there is plywood decking is laid across the rafters and fixed in place, then up stands are constructed along the gables to keep the soil in position. Bitumen based roofing felt is applied to the roof and is sealed with a waterproof mastic to ensure water tightness. Turf hooks are then screwed into the roof these are to hold the soils in position as the front edging boards are secured to these turf hooks. The membrane is laid across the roof then secured and sealed to ensure a fully functioning green roof. This membrane is what keeps the soil/substrate in position and the soil grows around this membrane. The roof is then ready for the soil to be poured over the roof then spread evenly over the roof. Finally the grass, turf or plants are laid over the soil. This is the general procedure for constructing a green roof on a domestic dwelling. Familiar examples of Green roofs 4
  5. 5. David O Dowd Green Roofs An example of a green roof is Manchester United’s player Gary Neville has just submitted planning permission for a passive house which includes a full green roof. This house is built into the side of a hill and the entire building is covered with a grass finish. It has been compared with the teletubbies house and criticised by the tabloids. This attitude by the tabloids is quite arrogant and obnoxious as this type of dwelling is the most sustainable type of house on the market when constructed. Papers and tabloids in particular should be applauding this type construction and encourage and steer people in the direction of sustainability. 5
  6. 6. David O Dowd Green Roofs References 1. Erik van Lennep 2008: A Green Roof Policy Guidance Paper For Dublin Draft guidelines for DCC to develop planning directives for the Incorporation of Green Roofs in new development Prepared by Erik van Lennep and Sinéad Finn Tepui, Dublin. 2008 2. A green roof model for building energy simulation programs D.J. Sailor 2008 published by Elsevier. 3. Vegetation development on extensive vegetated green roofs: Influence of substrate composition, establishment Method and species mix by Tobias Emilsson 2008 published by Elsevier. 4. een+roof.jpg 5. : Neville-unveils-plans-8m-Teletubby-eco-bunker-built- hillside.html#ixzz0fjXSMKsY 6. Neville-unveils-plans-8m-Teletubby-eco-bunker-built-hillside.html 7. content/uploads/2008/07/fukoaka02.jpg&imgrefurl= %25E2%2580%2593-a-fabulous-building-with-a-green- roof/25/07/2008&usg=__omj9KEbDa3fEXs9LCjs8dTHmslw=&h=375&w=499&sz=54&hl=en&st art=9&itbs=1&tbnid=OQlb5VbeOrwPjM:&tbnh=98&tbnw=130&prev=/images%3Fq%3Dgreen %2Broof%2Bat%2Bground%2Blevel%26tbnid%3DV0K5UlwLwVFySM:%26tbnh %3D0%26tbnw%3D0%26hl%3Den%26safe%3Doff%26sa%3DN%26gbv%3D2%26ndsp %3D18%26tbs%3Disch:1 8. gclid=CMGv9LPV958CFSIslAodoxtlYw 9. campaign=th_rss_design 10. architecture.php?page=1 11. glass.php 12. 6