Archive for category: Engineering

Since 1950, the world population has increased by more than double. The sprawling demographic shift due to continuous migration from rural to urban areas in developing countries imposes socio-economic and environmental pressures to the urban areas. Apparently, the high demand for housing and the unsustainable construction practices underlying its production in recent times constitute issues that merit the attention of low-impact green housing developments. The feasibility of such developments also lies in the effective use of low-cost green building materials and components (LCGBMCs),primarily because of their potential to conserve energy use, reduce life-cycle cost, lessen ecological footprints, and revive lost cultural traditions. Until recently however, only very few of these products have been widely established in mainstream, on account that most designers are constrained by their vaguely informed knowledge as to their sustainability impacts during the early stages of the design decision-making process, when most of the important decisions relating to sustainability are made. With the scale of complexity on how to incorporate sustainability principles in the early stages of the material selection decision-making process, and quest to stimulate the motivation for their use in a wider industry context, a clear gap is identified. Drawing on the concept of sustainability, this research aims to narrow the underlying gap by exploring and evaluating the significance of an integrated modular-oriented mode of assessment that is able to assist designers in developing an improved capability to make early-informed choices, when formulating decisions to select LCGBMCs at the early conceptual stages of the design process. With results derived from the relevant literature, industrywide surveys, and through empirical evidence gathered from interviews with a cross-section of house build stakeholders in Nigeria, key sustainability principle indicators impacting the selection of building materials are identified, analysed, grouped and ranked according to the relative importance that each decision factor holds, using a suite of statistical analytical methods. The information gathered from the analysis with inputs elicited from experienced professionals are used to develop a Multi-Criteria Material Selection Decision Support System (MSDSS), and later refined with feedbacks obtained from selected builder and developer companies. The above integration is enhanced using Macro-in-Excel Database Management System (DBMS), while the Analytical Hierarchy Process (AHP) model is adopted as the ideal assessment methodology, given its ability to transform objective and subjective variables into weighted scores. Expert surveys are then used to demonstrate the usefulness of the suggested decision support system. The applicability and validity of this model are further illustrated using an ongoing housing project in Nigeria. By comparing the outputs from the model to monitored data from the case study, it would emerge that LCGBMCs, when properly assessed with consideration of the key sustainability principle indicators (influential factors) at the early stages of the design decision-making process, could reduce the potential life-cycle carbon embodied energy of a typical residential housing project by nearly 40% and yield energy savings of roughly 30-50% per year, when compared to their conventional carbon-embodied equivalents. This study concludes that by addressing integration of sustainability principles into the material selection decision making processes at the early stages of the design, better support will be provided to key decision makers with the expectation of improved understanding and better informed choices, hence stimulate the motivation for more use of LCGBMCs in a wider industry context. The limitations of the study are highlighted and future research directions to better exploit the model capabilities are proposed.
Abstract:
There is a need to reduce the emissions of the country as a whole, to limit the risk of climate change due to Global warming and to meet targets set by the Kyoto agreement and the Climate Change Act. The large number of houses constructed annually in England and Wales have an important role to play in this. By reducing emissions, resulting from both the manufacture of construction materials and the energy used by house occupants, housing can help achieve the necessary emissions reductions. Alternative construction methods can contribute to this, either by having a lower embodied energy or by demonstrating good thermal properties to limit heat loss and hence operational energy. However, it is essential that both the construction industry and the public accept the alternative construction methods for them to be economically viable. In addition, there should be no loss of performance as a result of using alternative construction methods. Six methods of construction were studied in depth, including generating embodied and operational energy requirements and identifying their performance in terms of airtightness, wall thickness, and fire resistance. Public and industry acceptability were examined by use of questionnaires. A comparison of the data collected showed that identifying the best, or optimal, option visually is a challenging task as no single method of construction is best in all areas. A methodology was created to aid the selection of a wall construction method. The methodology is capable of examining multiple variables, in this work it is demonstrated with construction method and front building dimension. To identify the optimal method, optimisation by genetic algorithms is used. Use of the methodology was demonstrated with a case study based on the most frequently constructed housing type for England and Wales. The importance of weighting was demonstrated with the use of weightings based on concerns held by different parties. It was found that minimising the external wall area gives the optimal solution as less material is needed and there is less opportunity for heat loss. For the situation examined in the case study, Structural Insulated Panels (SIPs) were identified as having the potential to reduce the environmental impact of housing construction in England and Wales without impacting saleability or performance.
Abstract:
Low energy building methods, and the corresponding economic and environmental aspects, are an important area of consideration in many developed countries. Saudi Arabia characterized by its hot climates and geographical location in a global region renowned for its high energy consumption and carbon emission rates. Consequently, this research aims to foster the development of low energy housing in Saudi Arabia and establish a low carbon domestic design framework for Saudi Arabia that takes into account the local climatic conditions, context and socio-cultural challenges. In order to fulfil the above stated aims, this research establishes a definition system for low energy consumption in kWh/m² for the Saudi Arabian climate. To achieve the aims stated above, a comprehensive, four stage study has been performed. This investigation has attempted to: (a) identify factors resulting in high energy consumption in domestic buildings in Saudi Arabia; (b) identify the weaknesses of housing design in terms of architectural layouts and mass, house envelope design and construction materials used, and on-site renewable energy strategies; (c) establish and develop a low carbon domestic design framework that supports architects, civil engineers and building professionals in the design of sustainable homes for the Saudi Arabian climate, context and cultural requirements; and (d) propose three different, viable housing prototypes employing the established framework, thereby validating that framework through the identification of their energy consumption levels. Each stage of this research utilizes a specific methodology: public survey analysis; site visits and modeling analysis; expert consultation, using the Delphi technique approach; and the validation analysis approach. This study contributes to the body of knowledge within this field by offering a low carbon domestic framework for the design of low energy homes in Saudi Arabia. These findings are broadly applicable to other regions with similar climatic conditions and cultural requirements, such as those in the Middle East and GCC countries. The findings suggest that an energy reduction of up to 71.6 % is possible. Therefore, the system for low energy consumption level standards is suggested as a range between 77 kWh/m² and 98 kWh/m². The comprehensive economic and environmental benefits of these reductions have been analysed and benchmarked against the current situation in selected developed countries.