Prioritization of Facade Retrofit Measures to Achieve Energy Efficiency in Existing Office Buildings in Tehran

Addressing the problems of the inefficient existing buildings is of great importance in Tehran, where only a few buildings in the city are newly-built constructions. The existing building stock accounts for large energy consumption, and the problems of existing buildings are mostly related to the poor performance of the building envelope. The building facade, as the most significant part of the building envelope, considerably contributes to large thermal transmittance in existing buildings. As a result, studying the building envelope and especially the building facade can lead to considerable energy demand reduction in the building sector. Therefore, using facade retrofit measures can potentially reduce cooling and heating demand in existing buildings. This research tries to prioritize the facade retrofit measures based on their efficiency in reducing energy demand by adding thermal insulation, replacing windows, and adding shading to the south facade of the existing office buildings in Tehran. In other words, this research investigates the efficiency of the facade retrofit measures. It is hypothesized that using shading has more impact on reducing energy demand in south facades. This study is quantitative research drawing upon a parametrically performed simulation run by Energy Plus and Open studio in Rhino software with the help of Grasshopper plugin. The objectives were analyzed using Honeybee and Ladybug plugins. Also, a comparative study method was used to compare the energy consumption levels in retrofit scenarios and a reference model. The results show that adding shading is the most effective measure in facades with high heat transfer coefficients. In these facades, adding thermal insulation takes precedence over window replacement. Shading is still the most effective measure in facades with lower heat transfer coefficients; however, the window replacement should be prioritized to thermal insulation in retrofitting the existing facade with a higher heat transfer coefficient.