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Making Modeling More Meaningful in the Handbook

2021 Handbook Preview
Making Modeling More Meaningful in the Handbook

From ASHRAE Journal Newsletter, May 25, 2021

Occupant and multiscale modeling can help engineers more precisely model building energy use, but until now they were mostly absent from the Handbook—Fundamentals’ Chapter 19, Energy Estimating and Modeling Methods, said John Pruett, P.E., Member ASHRAE, Handbook subcommittee chair of TC 4.7, Energy Calculations. 

“Previously, occupant modeling was covered in a single paragraph, and multiscale modeling was not included at all,” said Pruett. “Both of these types of modeling will help engineers reduce the discrepancies between design or predicted energy performance and actual energy performance.”

Pruett discussed the new information with ASHRAE Journal and how this new modeling information could help reduce discrepancies between design or predicted energy performance and actual energy performance.

1. What new information does the updated Handbook chapter include?

Occupant modeling and multiscale modeling have both seen massive growth in interest and application over the past several years, but neither topic was covered well in previous editions of Handbook—Fundamentals.

Occupant modeling and multiscale modeling have been the subjects of some of the popular seminars at the past several ASHRAE Annual and Winter Conferences. These updates will provide much needed guidance on these topics and potentially lead to improved energy modeling results and applications.

2. What is occupant modeling?

Occupant modeling is the simulation of occupant behavior in building energy modeling (BEM). Occupant behavior refers to:

  • Occupant presence in spaces and movement between spaces;
  • Occupant interactions with building systems; and
  • Occupant adaptations (e.g., changing clothing, having hot/cold drinks).

Occupants’ expectations of satisfaction with the indoor environment drive their interactions with devices, equipment and energy systems in buildings—such as adjusting thermostat settings, opening/closing windows, turning on/off lights, operating window blinds, consuming domestic hot water and moving around—to satisfy their physical and nonphysical needs. These actions affect the built environment and energy use.

A clear understanding and accurate modeling of occupant behavior in buildings is crucial to reducing the gap between design and actual building energy performance.

3. What is multiscale modeling?

Multiscale modeling is the application of BEM across varying spatial scales—such as sub-building, building, district, urban, regional and national. The smallest scale can cover a single room or a component (e.g., window or wall) of building envelope, while the largest scale can cover the entire building stock of a region or a country.

4. What is the significance of the updated information on occupant and multiscale modeling?

Occupant modeling has been one of the more difficult parts of energy modeling, due to its diverse nature. Several research projects and studies of occupant behavior in recent years have led to the development of strategies for occupant modeling.

Multiscale modeling has seen a surge in interest in the past few years as more engineers and designers are being tasked with expanding energy analysis beyond the system and building level. There is much more focus on building interactions with other nearby buildings and other site features, such as for campuses and city-level analyses.

5. What are some examples of the technical content in the two new sections?

The occupant modeling section includes summaries of the different aspects of occupant modeling (occupant presence, occupant interaction with the building, occupant adaptations) as well as specific approaches and applications in building design and operation, including occupant-centric building design and control strategies.

The multiscale modeling section includes a breakdown of each scale and when each modeling scale is applicable. For example, sub-building scale modeling is useful to maximize the efficiency of specific portions of a building such as window glazing, whereas district scale modeling is useful to model systems shared by multiple buildings such as a district heating or cooling system.

The new information on both occupant and multiscale modeling includes several methods and tools to help engineers apply these types of modeling, including summaries of when certain methodologies may be more applicable than others. There are also numerous references and datasets listed that will further guide engineers in the application of these concepts as well as provide background information on their development.