Passive energy saving through thermal retrofitting of existing government office building envelopes - Case study for office-research building in Cairo, Egypt

Abstract

Egypt used several million kilowatts per hour of electrical power in 2023. According to 2022 data, public utilities and agencies used 15% of Egypt's power. Most of Cairo’s government buildings built in the 50th and the 60th of the last century are composed of reinforced concrete structure skeletons, flat concrete roofs, and burnt brick exterior and interior walls. At that time, building energy efficiency was not a priority. Thus, uninsulated building envelopes were built. Nowadays, renovating buildings requires increasing energy efficiency. Previous research showed that lack of thermal insulation in roofs, walls, window solar heat gain, and window frames thermal bridging increases heating and cooling costs. The current research aims to enhance existing buildings energy saving by improving thermal insulation of its envelope components. The existing research building in Cairo was assessed for environmental factors to accomplish the research goal. The research used a three-dimensional (3D) terrestrial laser scanner to assess building facades for creating an environmental study model. The research used the building office top floor construction as a comparative environmental simulation using (Design builder® version6 software) as a base case for yearly energy consumption due to heating and cooling loads, followed by improving the thermal insulation of each building element individually in the base environmental model and comparing its effect on annual energy saving percentage, then applying all of the best annual energy saving building envelope element thermal insulation retrofitting techniques to the improved building model. The research results showed that improving roof thermal insulation saves 33.5% of the yearly top floor total electrical energy, 12% for exterior walls, 0.75% for window glazing, and 1.56 % by retrofitting window frames. Applying all of the best energy-saving thermal insulation retrofit techniques to the whole structure saved 31% of annual energy consumption.