(Read the articles below. They will provide you with all the necessary information to do the tasks of the project)

Picture 1

GREEN ROOFS

What is a green roof? Surely the term does not refer to roofs which are just coloured green or covered with green tile or green shingles. A green roof, as an environmentally friendly construction, is a roof that is partially or completely covered with vegetation and a growing medium, planted over a waterproof membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems.

Container gardens with plants grown in pots are not generally considered to be true green roofs, although this is an area of debate.  A rooftop pond is another form of green roofs which are used to treat grey water.

The term green roof may also be used to indicate roofs that use some form of "green" technology, such as a roof with solar thermal collectors and a cool roof. Green roofs are also referred to as greenroofs, living roofs, eco-roofs, oikosteges, and vegetated roofs.

Picture 2

HISTORY

Though modern green roofs, which are made of a system of manufactured layers deliberately placed over roofs to support growing medium and vegetation, are a relatively new phenomenon, green roofs have a long history starting back centuries ago.

In Northern  Scandinavia green roofs or sod roofs Picture 3) have been around for centuries. A sod roof or turf roof consists of several layers of birch bark, which ensures that the roof will be waterproof, on gently sloping wooden roof boards with a layer of sod set on top. Sod is also a reasonably efficient insulator in a cold climate. So until the 19th century it was the most common roof on rural log houses in large parts of Scandinavia.

Picture 3

 The modern "trend" started in the 1960s when green roofs were developed first in Germany and then spread to many countries. Today, it is estimated that about 10% of all roofs in Germany have been "greened.” Green roofs are also becoming more and more popular in the United States, although they are not as common as in Europe.

As for  European Countries, many of them, including Germany, Switzerland, the Netherlands, Italy, Austria, Hungary, Sweden, the UK and Greece, have very active associations promoting green roofs, The City of Linz in Austria has been paying developers to install green roofs since 1983 and in Switzerland it has been a federal law since the late 1990s. In the UK their up-take has been slow but a number of cities have developed policies to encourage their use, notably in London and Sheffield.

Many green roofs are installed to comply with local regulations and government fees, often regarding stormwater runoff management. In rainy areas heavy storms can overload the wastewater system and cause it to flood. Green roofs decrease the total amount of runoff and slow the rate of runoff from the roof. It has been found that they can retain up to 75% of rainwater, gradually releasing it back into the atmosphere via condensation and transpiration, while retaining pollutants in their soil.

Combating the urban heat island effect is another reason for creating a green roof. Traditional building materials soak up the sun's radiation and re-emit it as heat, making cities at least 4 degrees Celsius (7 °F) hotter than surrounding areas.

The Chicago City Hall green roof (Picture 4), which is one of the earliest and most well-known examples of green roofs in the United States, was planted as an experiment to determine the effects a green roof would have on the microclimate of the roof. Following this and other studies, it has now been estimated that if all the roofs in a major city were "greened," urban temperatures could be reduced by as much as 7 degrees Celsius.

Picture 4

Green roofs are becoming common in Chicago, as well as New York (Picture 5) Atlanta, Portland, and other United States cities, where their use is encouraged by regulations to combat the urban heat island effect. In the case of Chicago, the city has passed codes offering incentives to builders who put green roofs on their buildings..

Green roofs have also been found to dramatically improve a roof’s insulation value. A study conducted by Environment Canada found a 26% reduction in summer cooling needs and a 26% reduction in winter heat losses when a green roof is used. In addition, greening a roof is expected to lengthen a roof’s lifespan by two or three times, according to Penn State University’s Green Roof Research Center.

Rooftop water purification is also being implemented in green roofs. These forms of green roofs are actually treatment ponds built onto the rooftops.

Green roofs can also provide habitats for different species of insects, birds and animals that otherwise have limited natural space in cities. Even in high-rise urban constructions as tall as 19 floors, it has been found that green roofs can attract insects, birds, bees and butterflies. Rooftop greenery complements wild areas by providing "stepping stones" for songbirds, migratory birds and other wildlife facing shortages of natural habitat.

Picture 5

Environmental Benefits

Green roofs are used to:

• Reduce heating (by adding mass and thermal resistance value);
• Reduce heat loss and energy consumption in winter conditions;

• Reduce cooling (by evaporative cooling) by fifty to ninety percent;
• Reduce stormwater run off;
• To create Natural Habitat;
• Filter pollutants and carbon dioxide out of the air which helps lower disease rates such as asthma;
• Filter pollutants and heavy metals out of rainwater;
• Help to insulate a building for sound; the soil helps to block lower frequencies and the plants block higher frequencies;

Financial Benefits

• Increase roof life span dramatically;
• Increase Real Estate Value;

Disadvantages

Whatever beneficial green roofs can be, certain disadvantages should also be taken into consideration. The main weak point of green roofs is the higher initial cost. Some types of green roofs do have more demanding structural standards especially in seismic regions of the world. As the weight load of the substrate and vegetation may exceed permitted static loading, the retrofit of some existing buildings can hardly be realised. Depending on what kind of green roof it is, the maintenance costs could be higher, but some types of green roof have little or no ongoing cost. Some kinds of green roofs also place higher demands on the waterproofing system of the structure both because water is retained on the roof and due to the possibility of roots penetrating the waterproof membrane.

However,  properly designed and installed systems include root barriers. It is true that installing adequate waterproofing systems and root barriers can increase the initial cost of the roof, but due to the fact that a green roof protects the waterproofing membrane from bad weather, UV light in particular, the life expectancy of the membranes is doubled or even tripled, and it leads to recovered initial cost differentials.

The Project

1. What is a green roof?

2. Exclude what doesn’t refer to green roofs:

3. Match the words with their definitions. Mind, one of the  definitions is extra.

4.The following layers make up a green roof. What are they used for and what is their correct order, do you think? (See Picture 2)

         a) drainage layer

         b) thermal insulation

         c) vegetation             -  1

         d) filter membrane

          e) growing medium

         f) waterproof layer

         g) structural support

5. Some facts are wrong in this article. Correct the mistakes.

1)The idea of green roofs is not new, it is centuries old. 2)Sod roofs first appeared in Northern Ireland. 3)But it was only in the 1990s that green roofs re-appeared in Europe. 4)First they spread in Austria, then in Germany. 5)Gradually they were installed in cities and towns in the United States and became even more popular than in Europe.

6)However, in most countries the up-take, i.e. the installation of green roofs was not warmly received and the governments had to encourage the developers by granting immunity from taxation to them.

7)Why are the governments so concerned with green roofs?

6. Look through the list of major benefits and choose the new ones not mentioned in the text. Then put all the benefits in order of importance for you.

1) creating oases of beauty

         2) insulation

         3) cooling

         4) cleaning the air

         5) space saving

         6) sound absorption

         7) food production

         8) providing a wildlife habitat

         9) storm water retention

         10) a place for urbanites to grow flowers and vegetables

         11) saving energy

7. What are the disadvantages of  green roofs?

8. Think of constructing green roofs in your place. Give arguments for and against the project.

ROLE PLAY

Group A:  you represent the government funding committee. Your task is to assess project proposals and to choose the best to provide its funding. You also have the right to decline both if neither of them meets the requirements.

You may find the following guidelines useful when assessing the projects.

Good projects should …

         1. improve the local environment;

         2. solve a problem/problems;

         3. need no, or little, annual financial support;

         4. offer ideas for future developments;

Group B: You represent the company "COOL ROOF” You install decorative intensive green roofs. Work out your project.

Group C: You represent the company "ROOF GARDENS”. You construct container gardens. Work out your project.

Each project should contain the following information:

Project title…………………………….

Project description…………………………….

Benefits of the Project ……………………….

Budget…………………………………………

Group D: You represent the local community. You wish your area could be beautiful, safe and green zone. You are aware of all the benefits of green roofs, but the majority of houses in your area not new and you are worried about the problems  the projects might cause.

Answer key:

1. – students’ own answers.

2. Green tile roofs, green shingle roofs, green coloured roofs should be excluded. Container gardens are not proper green roofs either.

3.   1f     2g     3i      4e      5h     6c     7j     8d      9b       "a”  is extra.

4.  1c     2e     3d     4a      5f      6b    7g

5.  2) Northern Scandinavia  3)in the 196  s 4) first in Germany  5)more common in Europe  6)The installment of green roofs is encouraged but greenroof companies are not free from taxes.

6. Numbers 1, 5, 7, 10 are not mentioned

7. – students’ own answers.

8. – students’ own answers.