In today’s world, where technology is rapidly evolving and people are becoming more concerned about cost and comfort, the demand for electricity for heating, ventilation, and air conditioning (HVAC) systems is on the rise. This puts a strain on efficient power grid management. Demand response strategies have become a critical solution to address this issue. One method is to utilize the inherent inertia of HVAC systems to regulate energy consumption intelligently. This paper presents an optimization model specifically designed for the Varennes Library in Quebec, which is a Net-Zero building. The purpose of the model is to evaluate the energy adaptability of the building and explore the interplay between various systems, such as a building-integrated photovoltaic array, a geothermal heat pump, and a thermal storage-equipped radiant floor system. The approach used to develop the model is based on a mixed-integer linear programming problem, which incorporates a resistance-capacitance (RC) model that describes the building’s thermal behavior. The model is validated through on-site measurements, which enable a rigorous quantitative analysis of the building’s potential flexibility, particularly under different weather conditions. The study assesses proposed control strategies in contrast to baseline measures, providing valuable insights into efficient energy management within the context of the Varennes Library.