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GREEN ROOFING A STEP TOWARDS SUSTAINABILITY

A green roofis a roof of a building that is partially or completely covered with vegetation and a

growing medium, planted over a waterproofing membrane. It may also include additional layers

such as a root barrier and drainage andirrigationsystems. (The use of green refers to the

growing trend of environmentalism and does not refer to roofs which are merely colored green,as with green roof tiles or roof shingles.)

ontainer gardens on roofs, where plants are maintained in pots, are not generally considered to

be true green roofs, although this is an area of debate. !ooftop ponds are another form of green

roofs which are used to treat greywater.

Also "nown as living roofs, green roofs serve several purposes for a building, such as

absorbing rainwater, providing insulation, creating a habitat for wildlife, and helping to lower

urban air temperatures and combat the heat island effect. There are two types of green roofs#

intensive roofs, which are thic"er and can support a wider variety of plants but are heavier andre$uire more maintenance, and e%tensive roofs, which are covered in a light layer of vegetation

and are lighter than an intensive green roof.

The termgreen roofmay also be used to indicate roofs that use some form of &green& technology,

such as a cool roof, a roof with solar thermal collectors or photovoltaic modules 'reen roofs are

also referred to as eco-roofs, oikosteges, vegetated roofs, living roofs, andgreenroofs.

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igure# rosssection of a green roof

Types of Green Roofs

'reen roofs can be categori*ed as intensive, &semiintensive&, or e%tensive, depending on the

depth of planting medium and the amount of maintenance they need. Traditional roof gardens,

which re$uire a reasonable depth of soil to grow large plants or conventional lawns, are

considered &intensive& because they are labourintensive, re$uiring irrigation, feeding and other

maintenance. Intensive roofs are more par"li"e with easy access and may include anything from

"itchen herbs to shrubs and small trees. &+%tensive& green roofs, by contrast, are designed to be

virtually selfsustaining and should re$uire only a minimum of maintenance, perhaps a once

yearly weeding or an application of slowrelease fertili*er to boost growth. +%tensive roofs areusually only accessed for maintenance. They can be established on a very thin layer of &soil&

(most use specially formulated composts)# even a thin layer of roc"wool laid directly onto a

watertight roof can support a planting of Sedumspecies and mosses.

Another important distinction is between pitched green roofs and flat green roofs. itched sod

roofs, a traditional feature of many -candinavianbuildings, tend to be of a simpler design than

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flat green roofs. This is because the pitch of the roof reduces the ris" of water penetrating

through the roof structure, allowing the use of fewer waterproofing and drainage layers.

Environmental Benefts

'reen roofs are used to#

Re!"#e $eatin% &'( a!!in% mass an! t$ermal resistan#e val"e)* A +,,- st"!('( Bra! Bass o. t$e Universit( o. Toronto s$o/e! t$at %reen roo.s #an alsore!"#e $eat loss an! ener%( #ons"m0tion in /inter #on!itions*

Re!"#e #oolin% &'( eva0orative #oolin%) loa!son a '"il!in% '( f.t( to ninet(0er#ent

es0e#iall( i. it is %lasse! in so as to a#t as a terrari"m an! 0assive solar $eatreservoir 1 a #on#entration o. %reen roo.s in an "r'an area #an even re!"#et$e #it(2s avera%e tem0erat"res !"rin% t$e s"mmer

Re!"#e storm/ater r"n o3

Nat"ral 4a'itat 5reation

Filter 0oll"tants an! #ar'on !io6i!e o"t o. t$e air /$i#$ $el0s lo/er !iseaserates s"#$ as ast$ma

Filter 0oll"tants an! $eav( metals o"t o. rain/ater

4el0 to ins"late a '"il!in% .or so"n!7 t$e soil $el0s to 'lo#8 lo/er .re9"en#ies

an! t$e 0lants 'lo#8 $i%$er .re9"en#ies

I. installe! #orre#tl( man( livin% roo.s #an #ontri'"te to LEED 0oints

A%ri#"lt"ral s0a#e

Financial benets

In#rease roo. li.e s0an !ramati#all(

In#rease real estate val"e

A green roof is often a "ey component of an autonomous building.

-everal studies have been carried out in 'ermany since the /01s. 2erlin is one of the most

important centers of green roof research in 'ermany. articularly in the last 1 years, much more

research has begun. About ten green roof research centers e%ists in the 3- and activities e%ist in

about 41 countries. In a recent study on the impacts of green infrastructure, in particular green

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roofs in the 'reater 5anchester area, researchers found that adding green roofs can help "eep

temperatures down, particularly in urban areas# adding green roofs to all buildings can have a

dramatic effect on ma%imum surface temperatures, "eeping temperatures below the /6//1

current form case for all time periods and emissions scenarios. !oof greening ma"es the biggest

difference7where the building proportion is high and the evaporative fraction is low. Thus, the

largest difference was made in the town centers.