Renée Azerbegi, CEM, LEED-AP®, Ambient Energy
As we move toward carbon-neutral buildings by 2030, optimizing all aspects of energy usage, including the programs that we use to model building performance, will be key. Part of the answer to creating carbon neutral buildings will be the widespread adoption of building analytical modeling (BAM) to create higher-performing buildings using building information modeling (BIM).
BIM for BAM
We are in a 3D world using programs such as IES-VE and Energy Plus, which can directly import files created in BIM-based programs such as Revit and SketchUp with much less error in architectural translation. With IES-VE, energy, daylight, airflow, and HVAC loads can all be examined. Also, IES-VE and Energy Plus model stratification, buoyancy, and surface reradiation so they can more accurately model chilled beam and other systems.
The key to successful translation of a SketchUp or Revit model to an energy model involves some key ground rules and a lot of communication. BAM should be an integral part of BIM meetings and consultant meetings so all design team members know how we are using the BIM model.
To understand what BAM is required, it is important to understand the owner's objectives:
Energy models have different uses at different design stages. Modeling during programming helps research architectural options—natural ventilation strategies, window-to-wall ratios, orientation, massing, etc.—that will really affect the design. Schematic design involves HVAC system analysis and daylight strategies. During design development, we look at more specific questions with more emphasis on the cost implications based on life cycle impact. Construction documents focus on compliance documentation. Construction administration focuses on the as-built model, if a client has set an energy use intensity goal or declared the project to be net-zero. LEED and Title 24 do not require an as-built model—a big problem in the energy community. For a LEED project the client typically paid for an end-of-design model only, unless the client pursued measurement and verification.
Daylight modeling is also done in Radiance models using Revit or similar gbXML. We use daylight modeling to create 100 percent naturally lit spaces so that we can turn the lights off during the day and save energy. We also use daylight modeling as a design tool to determine if a space will have too much glare, to determine how our daylight recommendations interact with our energy recommendations, and to determine the look and feel of a space aesthetically. We work closely with architects to recommend strategies that work cohesively with their design to optimize daylight in a space.
Computational Fluid Dynamics (CFD) Modeling
CFD is meant for analysis on specific airflow patterns and behaviors within a certain set of boundaries (usually a single room). CFD is also used for optimizing the placement of an exhaust duct or fume hood in relation to a supply, to prove underfloor air or displacement ventilation concepts, or for thermal comfort analysis.
Bulk Airflow Modeling
IES-VE is used to study room-to-room bulk air flow movement (MacroFlo) of natural ventilation systems. MacroFlo uses a zonal airflow model to calculate bulk air movement in and through the building, driven by wind- and buoyancy-induced pressures. Bulk air flow modeling is what is used to model natural ventilation and airflow behavior from room to room, and typically takes less time to simulate than CFD modeling.
In the end, understanding BAM capabilities and when to use what modeling process to optimize buildings will help us achieve the ultimate goal of carbon-neutral buildings sooner than 2030.
Renée Azerbegi is the president of Ambient Energy, and has 15 years of experience specializing in energy modeling, green building rating systems, life cycle costing, renewable energy, and mechanical design. Ms. Azerbegi's voluntary commitments to the green building industry currently include chair of the Awards Committee for the Colorado Renewable Energy Society, co-chair of the Energy Efficiency Building Coalition Energy Modeling Committee, and member of the International Facility Management Association's Sustainability Committee. Ms. Azerbegi has a master's degree in building systems engineering from the University of Colorado at Boulder, where she quantified both the economic and environmental impacts of LEED for her master's thesis, and a bachelor's degree in environmental science and geography from the University of California at Berkeley.
Ms. Azerbegi's current focus is on managing the California office, commissioning team, and Californian and other projects.