Energy modeling is necessary to determine the energy consumption of buildings and identify ways to reduce it. HOT2000 is an energy simulation modeling software developed and maintained by Natural Resources Canada that plays a pivotal role in Canada's home energy rating, labeling, and code compliance systems. This research examines the energy performance gap between modeling and actual energy consumption in two detached houses, located in Vancouver, BC were modeled with HOT2000 software. The architectural drawings were obtained from a design farm. It was observed that the actual energy consumption of the homes exceeded the predicted values by 40 to 45%. The discrepancies were attributed to the limitations of the energy modeling program, inconsistencies between the energy model and the actual buildings, and additional energy loads in the homes. Additionally, the study considers building performance under future climate scenarios, predicting an increase in energy consumption. Furthermore, this study conducted a parametric analysis of wall construction and energy sources to enhance energy efficiency. With just the change of energy source for space heating from Gas Boiler to Air Source Heat Pump (ASHP) the energy consumption dropped and saved 15 to 35% and CO2 decreased from 45 to 75% per year. Improving the wall R-value from R-14 to R-28 the space heating energy saved around 12 to 15%. Based on the energy modeling results, the South-facing house in Vancouver, BC, is more energy-efficient (~5%) than the north-facing house. Climate change is expected to intensify temperature extremes and fluctuations, which will likely increase the need for combined cooling and heating energy.