Building energy modeling(BEM) and building energy simulation(BES)

Building Energy Modeling (BEM)

Building Energy Modeling refers to the process of creating a computational model of a building (or a group of buildings) to estimate or quantify its energy use, to evaluate potential energy-saving interventions, and to ensure that it meets specific energy efficiency standards, codes, or criteria. BEM uses mathematical equations to represent the physical behavior of the building, such as heat transfer through walls, windows, and roofs, the efficiency of HVAC systems, lighting, and other appliances, and how these vary with time and weather conditions.

The output of a BEM can provide comprehensive insights into a building’s energy consumption patterns, identifying areas of high energy use and opportunities for improvement. BEM is often used in the early stages of building design to help architects and engineers make decisions that will improve the building’s energy efficiency. It’s also used for retrofit analyses of existing buildings to identify the most cost-effective energy-saving measures.

Building Energy Simulation (BES)

Building Energy Simulation is the application of the Building Energy Model. It uses the model to simulate the energy performance of a building over time, often a year, considering all four seasons and varying use patterns. The simulation process inputs local weather data, building operation schedules, and potential occupancy scenarios into the BEM to provide a realistic estimate of the building’s energy use and costs over time.

The BES can simulate different scenarios, such as changes in the building’s operation, the implementation of energy-saving measures, or variations in weather patterns, to see how these factors would affect the building’s energy use. The output of a BES is often used to generate an Energy Use Intensity (EUI) measure, which can be compared with similar buildings or used to verify if the building meets a specific energy efficiency target or standard.

In summary, BEM and BES are two critical tools in the toolbox of architects, engineers, and energy consultants working towards more energy-efficient and sustainable buildings. BEM provides the foundation, the mathematical model of the building, while BES uses this model to simulate the building’s energy performance under various scenarios and conditions.