Browsing by Author "Wijerathne, SN"

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item: Conference-Full-text
Amplification of comfort and the air quality with green roof in cities
(2013-12-06) Wijerathne, SN; Halwatura, RU
Since the last few decades the world population has been increasing in a faster rate. With the increasing population, the needs of the people have also increased. Because of that more people have lean towards to move to the cities in search of facilities. The demand for dwellings in the cities has increased. To accommodate this demand, more buildings have been constructed, changing the previous arrangement of the cities. The cities have turned into a compacted space with less vegetation and greenery. Yet again the pervious lands in the urban space have changed to impervious surfaces making the urban climate to be changed peculiarly in terms of temperature and air quality. The more the urban space has become industrialized, the more the air has been contaminated. There are other environmental issues together with the changes for the cities. Due to the increment of artificial surfaces the temperatures of the cities have been increased than the country side allowing the heat island effect to take place making the energy demands of the cities to be high. For these climatic problems the researchers have identified green roofs as a sustainable solution. This research mainly focuses on augmentation of air quality and on reduction of heat island effect, with the replacement of existing flat slabs in the Colombo city in Sri Lanka, with green roofs. A well compacted city area was chosen in the Colombo district. The measurements were taken in terms of temperature, humidity and CO2 in the chosen city. Different special places were chosen for the measurements. The obtained measurements are observed for the identification of the best remedy. With that the expected increment of air quality and expected reduction of the temperatures are modeled with the replacement of existing flat slabs in the area with green roofs. From the results it’s evident that the green roofs can play a major role in enhancing air quality and reducing heat island effect making people to live in cities comfortably and healthily.
item: Conference-Full-text
Effect of Different Ventilation Conditions on Indoor CO2 Levels
(2016-05-26) Sribanurekha, V; Wijerathne, SN; Wijepala, LHS; Jayasinghe, C
This paper describes a study on (Carbon Dioxide) CO2 levels based on different ventilation systems. Three main types of buildings were considered in the study, such as educational, office buildings and hospitals. The effect of different systems of natural ventilation systems on CO2 levels was studied. The measurements were taken by accommodating different situations in the open able condition of windows: fully opened, half opened and fully closed. It was found that, the size of windows, the number of windows and the positioning of windows have major impact on indoor air quality. CO2 measurements were taken in both naturally ventilated buildings and mechanically ventilated buildings. And a comparison was made between mechanically and naturally ventilated systems. In mechanically ventilated buildings two types of air conditioning systems namely cold water air conditioning system and spit type air conditioning system were considered for the comparison. Cold water air conditioning system was found to be good than the split type air conditioning system under improper maintenance conditions. From the experimental measurements we can conclude that the CO2 levels are higher in mechanically ventilated buildings which are not properly operated than in naturally ventilated buildings.
item: Conference-Abstract
The Impact of green roofs on urban heat island effect
(2016-10-12) Wijerathne, SN; Halwatura, RU
Growth of the world urbanization has been extensively accelerated since past few decades. With the increasing urbanization, the land with permeable layers and moist have been altered. As a result, urban heat island phenomenon has taken place, making the temperature in the cities to be higher than the country sides. Heat island effect in cities is mainly because of non natural heat absorbing materials use in buildings and other man made structures. Natural greenery in the cities was replaced by concrete yards and most of the cities urbanizing with more and more concrete. Since there is no space to grow, adding greenery to cities is also an issue. Having greenery over the roof or planting on roofs are now becoming popular in many countries. Green roofs play a major role as a sustainable solution to minimize the heat island effect. This paper discusses about the effects on the surrounding temperatures, if the existing flat roofs in the Colombo city, the capital of Sri Lanka, are replaced with green roofs. The reduction in the temperature in the atmosphere was calculated using actual measurements on small scale models and computer simulation. These findings were coupled with the energy balance of the city. From the results obtained, it can be clearly shown that there’s a significant reduction in the temperatures, in the city when compared to the prevailing condition. The forecasted condition proves that the foreseeable problem of urban heat island effect with the future developments can be drastically reduced with the introduction of green roofs
item: Article-Abstract
Mitigating the scale of urban heat Island effect in cities with implementation of green roofs
Wijerathne, SN; Halwatura, RU
Variations of the urban heat island effect is different from city to city. To understand the variations in the heat island effect, in the center of the Colombo City the capital of Sri Lanka, with the locations of buildings and roads, the temperature and humidity was measured with the height. A detailed analysis was done to find the specific height of which the heat island effect prevails and the temperature variations with height. With that a theoretical model was developed to identify the possibilities of controlling the heat island effect. The model was developed with replacing existing flat roof areas with green roofs, in randomly selected area (0.5Km2)in the Colombo City. These findings were coupled with the energy balance in the selected area and with a computer simulation. The reduction in the temperature in the canopy air layer in the roof level was calculated. The results show that there is a variation in the heat island effect with height. When, the vertical distance increases from the heating surfaces, the heat island effect is lesser. The heat island effect can be reduced with the implementation of green roofs in the Colombo City.
item: Thesis-Abstract
Performance of green roofs in tropical climatic conditions
(2016-05-02) Wijerathne, SN; Halwatura, RU
Growth ofthe world urbanization has been extensively accelerated since past few decades. With the increasing urbanization, the land with permeable layers and moist have been altered. As a result, urban heat island phenomenon has taken place, making the temperature in the cities to be higher than the country sides. Heat island effect in cities is mainly because of non-natural heat absorbing materials use in buildings and other man made structures. Natural greenery in the cities was replaced by concrete yards and most of the cities urbanizing with more and more concrete. Since there is no space to grow, adding greenery to cities is also an issue. Having greenery over the roof or planting on roofs are now becoming popular in many countries. Green roofs playa major role as a sustainable solution to minimize the heat island effect. This research discusses about the effects on the surrounding temperatures, if the existing flat roofs in the Colombo city, the capital of Sri Lanka, are replaced with green roofs. The reduction in the temperature in the atmosphere was calculated using actual measurements on small scale models and computer simulation. These findings were coupled with the energy balance of the city. From the results obtained, it can be clearly shown that there's a significant reduction in the temperatures, in the city when compared to the prevailing condition. The forecasted condition proves that the foreseeable problem of urban heat island effect with the future developments can be drastically reduced with the introduction of green roofs. Another problem the world is facing today is energy crisis. Because of that world is now focusing on the sustainable cities. The contribution of the green roofs towards the energy cost saving when it is implemented in the city level in the existing flat roof slabs is calculated. A Derob modeling is done and the AlC loads are obtained for different roof types throughout the year and with the actual roof areas obtained for the city the energy cost saving is calculated. The energy cost saving obtained was 12%. However when it incorporates with the actual practice the desires of the population also should be analyzed. Identifying the implementation possibilities of the green roofs in the city also is vital to achieve these identified benefits in the future. This was achieved through a detailed questionnaire survey. With questionnaire survey it was found that the awareness of the green roofs is 56.8% and the willingness to spend for a green roof is less than 20% than the existing cost for an asbestos roof.