Carbon Footprint of Green Roofing: A Case Study from Sri Lankan Construction Industry

Abstract

At present, the world is facing many hurdles due to the adverse effects of climate change and rapid urbanization. A lot of rural lands and villages are merged into cities by citizens, resulting in high carbon emission, especially in the built environment. Besides, the buildings and the construction sector are responsible for high levels of raw material consumption and around 40% of energy- and process-related emissions. Consequently, the interest in defining the carbon footprint of buildings and their components is on the rise. This study assesses the carbon footprint of a green roof in comparison to a conventional roof in a tropical climate with the aim of examining the potential carbon emission reduction by a green roof during its life cycle. A comparative case study analysis was carried out between an intensive green roof and a concrete flat roof located on two recently constructed commercial buildings in the Colombo district of Sri Lanka. Data were collected from interviews, project documents and past literature in addition to on-site data measurements and a comparison of life cycle carbon emissions of the two roof types was carried out. The results revealed that the operational phase has the highest contribution to the carbon footprint of both roof types. In the operational phase, the green roof was found to significantly reduce heat transfer by nearly 90% compared to the concrete flat roof and thereby contributed to an annual operational energy saving of 135.51 kWh/m2. The results further revealed that the life cycle carbon emissions of the intensive green roof are 84.71% lower compared to the conventional concrete flat roof. Hence, this study concludes that the use of green roofs is a suitable alternative for tropical cities for improving the green environment with substantial potential for carbon emission reduction throughout the life cycle of a building.

Greening of roofs as an adaptive measure for climate change

“…Indirect impact includes the long‐term effect of the green roof, which may include a reduction in energy consumption in buildings, leading to a reduction in the consumption of fossil fuels for heating 27 . On the contrary, some studies show that carbon emission during material production, material transportation and construction phase is high in green roof compared to conventional roof 33 . Therefore, it is necessary to study new materials whose production will be simpler and easier to transport, which will reduce CO 2 consumption.…”

“…27 On the contrary, some studies show that carbon emission during material production, material transportation and construction phase is high in green roof compared to conventional roof. 33 Therefore, it is necessary to study new materials whose production will be simpler and easier to transport, which will reduce CO 2 consumption. This topic is described in more detail in Chapter 3.4 LCA.…”

Analysis and Valuation of the Energy-Efficient Residential Building with Innovative Modular Green Wall Systems

“…The arrangement of green wall systems on the buildings is a method to improve the quality of the urban space [16]. The wide range of benefits is associated with green wall systems, including performed technological systems with organizational structures and the reduction in airborne noise and energy cost savings by 40% [19][20][21][22][23][24][25][26]. The effectiveness of green roofs in reducing building energy consumptions in different climatic conditions was investigated [23,24,27].…”

Green roof as a technology towards sustainability: A perspective of benefits offered

“…To date, only a few studies have examined the different aspects of green roofs in the Sri Lankan buildings. Halwatura (2013) and Dareeju, et al (2011) investigated the benefits offered by extensive green roof type while Nadeeshani, et al (2021) assessed the life cycle carbon emission of an intensive green roofs based in Sri Lanka. However, other benefits offered by intensive type were not explored locally.…”