Performance of Building Roofs on Energy Efficiency – A Review

Comprehensive Study the Potential of Green Roof System

“…USA has published 34 % of total research journals. European Union and Asian countries contribute 33 % and 20 % respect ively [22]. …”

“…In 1970 the modern type of green roofs was introduced designed and developed in Germany .At same time green roofs became popular in France, Switzerland and north America .Japan has implemented green roof to reduce the effect of urban heat island [14]. Most of the early information of development and design of green roofs was written in German language which is not available.Germany is increasing green roof approximately 1.5 million square per meter per year [22]. In Germany more than 10% buildings have green roofs [1].In the first phase 1% of green roofs were implemented end of 19 th century and at the large scale implementation is done in from 1983-1996 (Kohlar ,2006) .In Britain green garden is used in built up area so any can provide garden on the roof of the building [1].Nowadays some of the country like America ,Australia ,Japan , Singapore and Canada are applying green roofs very intensively .In the Basel city 15% of the green roofs have been established .In Toronto city according to by-laws for the new construction of more than 2000 square meter the implementation of green roof 20-60% of the roof is compulsory .…”

“…Plants can reduce air pollution, energy load on air condensing, carbon dioxide [22].Vegetations decrease the cooling demand in summer and heating demand in winter and increase the thermal comfort inside the building [5].The foliage of vegetations absorb a part of solar radiation for photosynthesis process which is a biochemical characteristic of plants .Foliage of plants act as a shading device decrease the impact of solar radiation [8]. …”

“…All the different types of green roofs require different depths of growing mediums and different types of vegetations [Banting et al,2006] .Some important characteristics features of extensive green roof plants - (1) They are short in height and mat formatting (2) Their roots are shallow (3) Their leaves able to store water (4) they grow fast [ Maclvor and Lundholm,2011].To establish extensive roof we do not desire extra structure support. These roofs are least economic, very low maintenance cost and establish in short time [ 22] .There are four types of plants which have these characteristics (1) Moss Sedum plants (2) Sedum moss herbaceous plants (3) Sedum herbaceous grass plants (4) Grass herbaceous plants.These types of plants require 2 cm to 20 cm depth of thin growing medium [ Banting et al,2005 ] .Another four types of plants like grass herbaceous plants, wild shrubs coppices ,shrubs and coppices are require deeper growing medium 12cm to 100 cm these types of plants are suitable for semi intensive green roofs .These roof require high capital cost in establish and maintenance [22].The vegetations of intensive green roofs can be medium and large size shrubs canopies small trees this kind of vegetation require deeper growing medium 15 cm to 200 cm [ Banting et al,2005 ]. Due to tall height of plants and trees deep growing medium this types of intensive green roof require large capital cost in establish,maintenance, building structure ,fertilising weeding and watering [22] .…”

“…These roofs are least economic, very low maintenance cost and establish in short time [ 22] .There are four types of plants which have these characteristics (1) Moss Sedum plants (2) Sedum moss herbaceous plants (3) Sedum herbaceous grass plants (4) Grass herbaceous plants.These types of plants require 2 cm to 20 cm depth of thin growing medium [ Banting et al,2005 ] .Another four types of plants like grass herbaceous plants, wild shrubs coppices ,shrubs and coppices are require deeper growing medium 12cm to 100 cm these types of plants are suitable for semi intensive green roofs .These roof require high capital cost in establish and maintenance [22].The vegetations of intensive green roofs can be medium and large size shrubs canopies small trees this kind of vegetation require deeper growing medium 15 cm to 200 cm [ Banting et al,2005 ]. Due to tall height of plants and trees deep growing medium this types of intensive green roof require large capital cost in establish,maintenance, building structure ,fertilising weeding and watering [22] . In various types of green roofs extensive roof are least expensive, lowest weight and minimal maintenance required and easy to install .Their vegetation require minimal irrigation [1].…”