A study for thermal performance evaluation of building envelope in terms of summer comfort conditions in hot-dry climate

Increased energy consumption has led to reduction of natural resources; therefore, cost of energy has increased. Greenhouse gases, as a result of excessive consumption based on fossil energy resources, causes air pollution and absorbs sun light in the atmosphere after the reflection on earth and this is one of the main reasons of climate change. Major part of energy consumption arises from the heating and cooling systems of buildings to provide thermal comfort conditions. There have been many global studies to reduce energy consumption in buildings via various regulations and standardizations. "Regulation of Energy Performance in Buildings", started in Turkey in 2009, references TS 825 Thermal Insulation Requirements for Buildings. However, a building that is suitable for TS 825 criteria, may still need a mechanical cooling system as it might face with overheating problems in summer and therefore violate thermal comfort conditions. Impact of climate change has been observed all around the world recently. Besides, cities transformed into heat islands as a result of excessive construction and unplanned urbanization. Therefore, cooling energy consumption has increased not only in hot climates, but also in mild climates. Many global researches show that it is important to focus precautions related to building envelope, during the undesired heating period, when day & night temperature difference is high. In an energy efficient design, it is important to control building envelope that separates indoor and outdoor environment and determines energy expenditures by controlling heat transmission. Using sun light control mechanism in facade prevents sun light when heating is not desired and this is one of the mostly used methods in building envelope to reduce cooling energy consumption. Another precaution is increasing the performance of building envelope for summer comfort conditions and designing the building envelope for minimum cooling energy consumption by controlling its dynamic thermal conditions. In this study, it is aimed to evaluate summer comfort conditions to reduce cooling energy consumption in a building in Diyarbakır, the representative city of hot-dry climatic zone in Turkey. "Dynamic Thermal Properties Calculator" software, which is suitable for calculation methodologies in "EN ISO 13786" and "EN ISO 13790" standards, is used to calculate dynamic thermal properties of building envelope. In order to calculate summertime cooling load, air temperature and inside surface temperature values, Design Builder software is used. This software is an interface of EnergyPlus, which utilizes heat balance method algorithms. Based on calculations, annual cooling loads, and daily/weekly inside air – inside surface temperature changes are compared for different building envelopes in terms of dynamic thermal properties of building envelopes. This study consists of five sections: In the first section, reasons and consequences of high-energy consumption, its effects on energy consumptions in buildings, and worldwide energy efficiency strategies are examined. In addition, objectives of this study, literature review, and initial hypothesis are presented. In the second section, energy consumption in buildings depends on the desire of the users for suitable comfort conditions to maintain their physical and mental performance is discussed. Energy efficient design parameters, which affected thermal performance of the building envelope in hot–dry climates, are defined in terms of user, climate and the building, and dynamic thermal properties of building envelope are explained. In the third section, steady state, semi-dynamic and full dynamic cooling load calculation methods in hot–dry climates, where cooling energy consumption is much higher, are explained in order to define thermal performance of building envelope. Softwares developed by using these methods are introduced. As it is so important to analyze heat transfer process in order to understand complex structure in cooling energy consumption calculations, amount of thermal mass effect and its working principle within the scope of different calculation methods are examined. Fourth section contains a case study to evaluate the summer comfort conditions for reducing cooling load in a building in Diyarbakır, the representative city of hot-dry climatic zone in Turkey. In this case study, different modern and traditional building envelope alternatives with the same U value are developed and dynamic thermal properties are calculated for all envelope alternatives. Then, annual cooling energy consumptions are calculated for the model building. Utilization of different main materials and internal covering materials for walls, which designed by the same heat transmission coefficient, has an effect on annual cooling energy consumptions. This effect is contextualized with dynamic thermal properties of the building envelope. At the final phase of the case study, building envelope alternatives which have the lowest cooling energy consumption results, are chosen from each material group and thermal comfort conditions are evaluated with internal air temperature and inside surface temperature graphics. In the fifth section, overall results of this study and the recommendations to reduce cooling energy consumption for buildings in hot-dry climate are presented. Subjects and proposals are refered for the future studies. All backup calculations and results for summertime cooling loads and dynamic thermal properties of building envelope combinations developed in this study are given in tables in the appendix section. As a result of this study, it is aimed to take architects and engineers' attention on energy efficient design approaches, against the climate change and its negative consequences.