Comparative evaluation of prefabricated panel wall system with on-site construction wall system in the context of environmental impact and energy consumption

The increase in the world population, the rise in energy consumption and the rapid consumption of resources have brought many global problems to the agenda, and the solutions sought for environmental problems have become one of the most important movements of the current century. The construction sector is one of the sectors with the highest responsibility for energy consumption and environmental problems. For this reason, alternative environmentally friendly material technologies and construction systems are on the agenda of researchers. Founded in the 19th century and started to be used in the 20th century, "pre-manufactured construction" is one of the alternative construction methods. The advantages of industrialisation and mass production in construction have been realised by developed countries, especially in Japan, Scandinavia and the USA, and prefabricated construction systems have started to be applied and researches to improve the system have continued. Prefabricated construction systems, which are relatively rare in our country, have been defined by making use of the studies in the literature and it has been seen that it is a subject open to development. There are many reasons why prefabricated construction systems are not widely used in Turkey. The most prominent reason is that there is a prejudice in the society and the sector about this construction system, which is relatively new for our country. The prejudice stems from the lack of sufficient theoretical and practical knowledge on this subject. In addition, since the upfront investment cost of prefabricated construction systems is high, there is an idea that it will be much more expensive to build with this construction system. However, when detailed research on the system is carried out, it is seen that in case of mass demand and mass production, prefabricated construction system, like all industrialised systems, provides economic benefits. In addition to the economic benefits, its low environmental impact defines it as a more sustainable and environmentally friendly construction system. At a time when our world is being damaged by mankind every day, the promotion of sustainable construction systems in every country will benefit everyone globally. The aim of this thesis is to investigate the energy consumption and environmental impacts of the prefabricated construction system, which has advantages in terms of speed of construction, efficient use of resources, good organisation and predictable results, quality control, low construction site impacts, increased occupational safety, recycling - reuse and waste management. With the results of the research, it is aimed to contribute to the literature on prefabricated construction systems, about which there is a lack of information and prejudices In the first chapter of the thesis, the aim and objective of the thesis are explained and the method of the thesis is defined. In the second chapter, the concepts of prefabrication and modular construction are defined, the classification approaches of prefabricated systems are compiled, and findings on the status of prefabricated construction in Turkey and in the world are presented. The third chapter of the thesis is the part where the concept of environmental impact is explained and information is given about the methods used to measure environmental impacts. It is seen in this chapter that the construction sector has a great responsibility in terms of energy consumption and greenhouse gas emissions. Life cycle assessment as a holistic environmental impact measurement tool is explained here. As a case study, single prefabricated houses mass-produced and catalogue-sold by local prefabricated house manufacturers in Turkey are discussed and compared with the conventional on-site construction - reinforced concrete frame infill wall - single house models. The standard physical properties of the mass-produced prefabricated houses and the system specifications commonly used in Turkey for the construction of onsite-built houses have been determined, and four different building models, two prefabricated and two onsite-built models, have been created in total. The modelled buildings are single storey single dwelling buildings of 116 square metres in size and have the same foundation and roof structure. The prefabricated construction models are constructed with a light steel structural system and prefabricated panel walls. Prefabricated panel wall layers are polyurethane foam material between two fibre cement panels or cement bonded particle boards. Since the wall panels are produced as a flat surface in the factory, they do not require plaster application. In on-site construction models, reinforced concrete frame carrier system and infill walls are used. Infill wall materials are aerated concrete or brick. The wall surface is plastered and XPS insulation material is applied to the exterior facade. This requires re-plastering of the surface. The One Click LCA software for life cycle assessment is a comprehensive analysis programme with a database of technical values of materials from manufacturers from many countries. With this software, the lifetime emissions of four building models were calculated and compared. "EnergyPlus" software, which provides energy modelling in buildings, was used to calculate the U-factors of the walls of the designed models, the total site energy of the buildings and the total source energy of the buildings. For the work time, material and labour cost analysis, calculations were made according to the price tables published by the ministry and the information of the manufacturer companies was consulted. When the results obtained from the energy simulation are compared; it is seen that the prefabricated construction models, despite having a much thinner cross-sectional shell, catch the energy performance of the on-site construction models for Istanbul, which is located in the second degree day zone. When lifetime emission, work duration, material and labour cost parameters are considered, the superiority of prefabricated construction models is observed. The analyses are compared in detail in the last section of the fourth chapter. As a result, it is seen that the prefabricated system has a significant advantage in terms of cost and construction speed while causing less damage to the environment in terms of emissions, and it is revealed that it is a system that should be used more in the future. In order to break the prejudices, it is recommended that the system should be promoted by official institutions, a construction regulation for light steel prefabricated houses should be established, steps should be taken to eliminate the lack of information on the subject, students and existing professionals should be supported with trainings on the subject and this construction system, whose benefits have been revealed, should be applied as an alternative to the traditional construction system.