An Analytic Study of the Effect of Envelope Insulation on Annual Energy Consumption in Tall Office Buildings of Tehran Metropolitan City

Buildings account for almost 40% of global energy consumption and are the major contributor to the world’s greenhouse gas emissions. Most of the measures taken to reduce energy consumption in buildings are somehow active and mechanical strategies, which lead to the increase of construction costs for employers. Regarding the importance of the role of architects, if the initial decisions through design process are made based on environmental issues and climatic approach, considerable saving on cost and energy consumption can be achieved. In spite of the fact that high-rise construction in large cities of Iran such as Tehran, along with the rest of the world, is being developed, however, its consequences, including the considerable waste of energy resources has not been properly recognized yet. Furthermore, the recent implementation of the fuel subsidies law in our country, makes it necessary to undertake essential researches as well as to demonstrate the practical frameworks, more than before. In this regard, the main concern of the research was around the designing of energy efficient tall office buildings in Tehran. For this purpose, according to the extent of the related fields, the effect of envelope layers were specifically evaluated on the annual energy consumption. The building envelope is one of the most significant components of a building that affects physical properties, thermal and environmental behavior as well as energy consumption. As a result, making accurate decisions in this regard is essential, especially for high-rise construction due to its high amount of building cost and materials. In order to achieve the aforementioned objectives, different research strategies and methods were applied in each step of the research process involving desk study, comparative analysis, case study and energy performance simulation, and data interpretation was implemented using descriptive statistics and logical arguments. In this research, the features of the base-case model for energy simulation was determined through the desk studies and field surveys conducted on Tehran office buildings. Ecotect 2011 software was firstly used for 3D modeling and Energyplus 8.2 was utilized to simulate the thermal aspects as well. At the beginning of simulation process, according to the results of the previously conducted researches, 15 common wall types were considered as independent variables for analyzing the impact of each alternative on heating and cooling loads. The simulation results showed that the impact of internal insulation on the reduction of heating and cooling loads is much greater than the external one. Moreover, wall exterior insulation can significantly reduce the annual energy consumption for heating and cooling. Due to the slight temperature changes along with the building height, it is not economical to use different wall insulation details. The study results generally demonstrate the considerable effect of insulation component on the building energy consumption in the climatic conditions in question. Based on the findings, the impact of insulation thickness on reducing annual energy consumption is more considerable than the impact of wall block thickness. Finally, a table of four optimum wall details was introduced for a tall office building envelopes in Tehran metropolitan city.