Combining BIM and BEM in Design
Worldwide, companies are using building information modeling (BIM) processes to improve and increase productivity in designing and constructing building projects. As additional benefits, cost reductions are being realized, and errors are being caught and remedied before construction begins.
Because there is growing public interest in energy conservation in buildings, BIM platforms are increasingly integrating building energy modeling (BEM) at the design stage. In a white paper co-authored by Autodesk, the BEM process is described as being supported by building dimensions, location and weather information.
Measuring building performance and including more information on the energy usage by the building’s equipment will enable the refinement of BEM accuracy within BIM. The overall results will be better informed design decisions and the creation of comprehensive ‘digital twins’ for better facility operations and maintenance. After project handover, teams can have a complete, unified view of all the building’s architectural and energy features.
Customer expectations are driving energy conserving features and improvements over the entire lifecycle of built assets, and that becomes more achievable with digitization and standardization enabled by BIM processes.
In the traditional construction scenario, energy usage has been approximated, but the true performance is usually different than the estimates used in planning. The use of 3D modeling in the BIM process makes operational data more detailed and accurate – from architectural components to all mechanical, electrical and other internal systems. Stakeholders can be on the same page, and information can be shared among teams for maximum collaboration. In addition, construction can be sequenced for improved efficiency.
The Autodesk white paper reported that more than half of architects and engineers believe BIM increases contractors’ understanding of design intent; nearly two-thirds of owners and contractors agree that BIM improves the accuracy of estimating construction costs.
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According to the Office of Energy Efficiency & Renewable Energy (OEERE), BEM is a physics-based software simulation of building energy use. It is being used in new construction and remodels for green certification, tax credit qualification, code compliance, utilities incentives, and real-time building equipment controls.
Whether BEM tools are integrated into BIM or used externally, they consider:
- the building’s structure and geometry
- rooms, zones and building envelope
- construction materials
- lighting, HVAC and water heating
- renewable energy generation systems
- efficiencies of equipment
- control strategies
The BEM process also considers the building’s use and operation, occupancy, plug-loads, and thermostat settings. When combined with local weather data, the BEM tool calculates thermal loads, system response to those loads and resulting energy use. Other metrics, such as occupant comfort and energy costs, can also be included.
As the Autodesk white paper points out, one thing that affects the integration of BEM with BIM is the lack of an established standard or database that defines energy-related properties for modeling energy usage. The OEERE website states there have been local initiatives in France, Germany and Australia, with more countries expected to follow suit with their own standards.