This study investigates the influence of the building envelope on the energy usage of a chosen building using the simulation program TRNSYS. The building located at Carleton University, Ottawa, Canada is a small building retroffited as part of the Natural Resources Canada’s Prefabricated Exterior Energy Retrofit (PEER) project. The project\u27s aim is to develop prefabricated technologies to be used for retroffiting existing building envelopes of homes in Canada. The thermal resistance (RSI) of the existing walls were improved from 1.80 m2K/W to about 6.40 m2K/W after installation of the prefarbricated retrofit wall system. Analytical verification of the whole building performance simulation software is performed using a solitary heat transfer mechanism under simplified boundary conditions with known analytical solution. The warm-up period necessary to ensure heat is distributed in the building thermal mass at the start of the simulation is quantified. The thermal performance of the whole building envelope is quantified using the time-lag effect and decrement factor and energy requirement for heating and cooling
