By Ruwan Laknath Jayakody
Since the most significant building component that contributes to the global warming potential (GWP) is the building of walls which involves both exterior and interior masonry work, a local research has recommended the identification of alternative building construction materials and practices for building walls that would in turn result in a lower negative impact on the environment.
This finding and recommendation was made by Engineer K.S.L. Wickramaratne (attached to the Sustainable Built Environment Programme Postgraduate Unit of the Department of Civil Engineering of the University of Peradeniya) and Senior Lecturer in Manufacturing and Industrial Engineering at the same University, A.K. Kulatunga in an article titled Building Life Cycle Assessment (LCA) to Evaluate the Environment Sustainability of Residential Buildings in Sri Lanka which was published recently in the Engineer: the Journal of the Institution of Engineers, Sri Lanka. The study assessed the environmental impacts of typical residential house construction designed for low income families in Colombo using economical construction materials.
As explained by Wickramaratne and Kulatunga, LCA is a technique and scientific tool for assessing the environmental burdens and impacts associated with a specific product, process or activity (such as those of the building sector) by identifying and quantifying the energy and the materials used, and the wastes released to the environment. This is done by, as noted by M. Asif, T. Muneer and R. Kelley in LCA: A Case Study of a Dwelling Home in Scotland (2007), assembling an inventory of the relevant inputs and outputs throughout its life cycle. In turn, this helps to ultimately achieve, as mentioned by M. Khasreen, P. Banfill and G. Menzies in LCA and the Environmental Impact of Buildings: A Review (2009), sustainable building practices. The International Organisation for Standardisation (ISO) Standard 14040 of 1997 defines LCA as a technique for assessing the potential environmental aspects associated with a product or service by compiling an inventory of the relevant inputs and outputs, evaluating the potential environmental impacts associated with these inputs and outputs, and interpreting the results of the inventory and impact phases in relation to the objectives of the study.
There are, as pointed out by L. Pinky, S.M. Reddy and S. Palaniappan pointed out in the Application of LCA for a Residential Building Construction (2012), four steps necessary for a complete life cycle study which include the goal and scope definition (including the definition of the functional unit and the system boundary), the life cycle inventory (preparation involves data collection and calculations to quantify the material and energy input and outputs of the building’s life cycle), the life cycle impact assessment (evaluates the significance of potential environmental impacts), and interpretation (results will be given along with the conclusions and recommendations).
Wickramaratne and Kulatunga explained that since the life span of residential buildings in Sri Lanka varies from region to region based on the construction technology, the system boundary of this study is chosen as from the cradle to the gate (assessment of a partial product life cycle from resource extraction {cradle} to the factory gate - before it is transported to the consumer).
The case study by Wickramaratne and Kulatunga presented the cradle to the gate LCA study based on a low cost (for a low income family) residential building envelope which is designed to be constructed in Colombo. The functional unit of the study is a single storey, two bedroom house with 400 square feet (37.16 square metres) of floor area.
As revealed by Asif et al., R. Kumanayake and H. Luo in the Cradle to Gate LCA of Energy and Carbon of a Residential Building in Sri Lanka (2018), and J. Monahan and J. Powell in An Embodied Carbon and Energy Analysis of Modern Methods of Construction in Housing: A Case Study using a LCA Framework (2011), reinforced concrete is the highest contributor to the total embodied energy and carbon of a building. A.F.D. Rashid, S. Yusoff and N. Mahat found in A Review of the Application of LCA for Sustainable Buildings in Asia (2013) that the operational phase consumes the highest energy throughout the 50 years life span of buildings. Pinky et al., pointed out that a few studies had concluded that building envelope (external and internal masonry work) is the most significant building component. Rashid et al., and A. Utama and S. Gheewala’s Life Cycle Energy of Single Landed Houses in Indonesia (2008) showed that clay-based products work much better than cement-based products throughout the whole building life cycle.
Even though local housing development projects (by the Governments of Sri Lanka and India, the United Nations Human Settlements Programme or Habitat, the Habitat for Humanity Sri Lanka organisation, etc.) plan to construct residential housing units on the scale of thousands in both urban and rural communities, the lack of attention towards environmental sustainability, Wickramaratne and Kulatunga notes, raises serious concerns among the said communities.
The scope of this study includes the pre-building phase (the extraction of raw materials, transportation, the manufacturing of components, transport to the site and construction work), the building phase (occupation and use, and maintenance and renovation) and the post building phase (building demolition, and recycle, reuse and disposal).
The relevant inputs and outputs within the selected system boundary included raw materials, energy, wastage, auxiliary materials, etc. Building components and materials used for the low cost residential building are rubble masonry work for the rubble foundation, a concrete floor plus rendering with tiled bathroom for the floor and floor finishes, cement block walls for the external and internal walls, timber for the main door and polyvinyl chloride (PVC) for the internal doors.
For this typical residential building construction work, all the necessary drawings were drawn by a chartered architect using a computer aided design and drafting software application (AutoCAD), including the ground floor plan, foundation design, roof design, etc. The required amounts of construction materials, such as the number of cement blocks, ceramic tiles and asbestos roofing sheets, were calculated using the floor area and roof area values provided in the drawings. The summarized life cycle inventory data included rubble stones, cement, sand, metal crushed stones, water, cement blocks, putty, primer paint, weather bond paint, emulsion paint, tile adhesive, ceramic tile, timber, PVC, glass, asbestos, brass, and craft paper.
The standard cement to sand ratio values mentioned in the relevant specifications for building works were used for evaluating raw material quantities (such as cement, sand, water, metal, etc.) used for mortar for block work, rubble foundation work and wall plastering work, etc. Material coverage technical specification data sheets were used to calculate the required amount of materials for finishing works including emulsion paint, primer, skim coat, tile adhesive, etc. The transportation data for delivering each construction material to the specified site location was also added into each assembly (building component) individually. Furthermore, it was assumed that no electrical or mechanical equipment was used for this construction work and that only manual labour was involved.
The house is divided into seven components, namely, the rubble foundation, floor and floor finishes, external walls, internal walls, doors, windows and roof.
The foundation for the building is based on general rubble masonry work. The house consists of a concrete floor with cement rendering and a bathroom with a tiled floor. The external and internal walls are made out of cement blocks with 200 millimetres (mm) and 100 mm thickness, respectively. A timber main door and PVC internal doors with windows made out of timber and glass are used. An asbestos roof is used.
GWP is, as emphasised by Wickramaratne and Kulatunga, one of the most important environmental impact categories in the construction sector.
Applicable environmental problems include those such as climate change and the impact on human health and eco systems, human toxicity, photochemical oxidant and particulate matter formation, ionising radiation, terrestrial acidification, freshwater eutrophication, terrestrial, freshwater and marine eco toxicity, agricultural and urban land occupation, natural land transformation, and ozone layer, metal and fossil depletion. In terms of damage assessment, impact indicators represent overall impacts on human health, the eco systems and resource depletion.
It was found that the external walls contribute 100% for the GWP while internal walls contribute 57.56% to the GWP. This result, Wickramaratne and Kulatunga elaborate, shows that building walls (exterior and interior masonry work) constitutes the most significant component in terms of the GWP.
External walls also show a more than 50% contribution to all indicators except agricultural land occupation (40%) and metal depletion (15%). Building external walls is thus identified as the most significant building component in terms of environmental impacts, Wickramaratne and Kulatunga reiterated. Building internal walls shows the second highest contribution.
The external wall component was the most significant building component with the highest contribution to all three damage categories including having a 58.9% contribution towards human health, a 56% contribution to ecosystems and a 59.8% contribution on the resources. The internal walls component shows the second largest contribution with 33.3% for human health, 32% on ecosystems, and 32.8% concerning resources. Therefore, Wickramaratne and Kulatunga note that during the eco design process, more attention needs to be given to the external and internal wall component of the building.
This knowledge, Wickramaratne and Kulatunga observe, can be used for future large scale human settlement projects and to achieve environmental sustainability in high rise economical and residential building construction works in the built environment.
Sri Lanka needs alternative wall building methods, materials to reduce global warming: Study
27 May 2021
Sri Lanka needs alternative wall building methods, materials to reduce global warming: Study
27 May 2021