How CBECS Data Affects Standard 90.1 Development and Implementation

Interview by Mary Kate McGowan, Managing Editor

From ASHRAE Journal, January 2021

In November, the U.S. Energy Information Administration released the first estimates from the 2018 Commercial Buildings Energy Consumption Survey (CBECS), which provides information about the U.S. commercial building stock.

Public and private organizations use this data for energy use planning and forecasting. ASHRAE analyzes this data for use in the Handbook and standards. The data can also be used to quantify the energy reduction impact of the most recent versions of ANSI/ASHRAE/IES Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, and to identify building types and opportunities for energy savings for future versions of Standard 90.1.

Members of Standing Standards Project Committee (SSPC) 90.1, including Don Brundage, P.E., Member ASHRAE, chair of SSPC 90.1; Richard Lord, Fellow ASHRAE, co-vice chair of SSPC 90.1; Michael Rosenberg, Fellow ASHRAE; and Len Sciarra, AIA, Member ASHRAE, discuss how CBECS affects Standard 90.1’s development and implementation.  

1. What is the significance of the most recent CBECS?

CBECS is a very important information source on energy use and equipment stock in the United States for nonresidential buildings.  It is used in countless different planning activities related to energy use and forecasting by many different public and private organizations. CBECS is produced by the Energy Information Administration, part of the United States Department of Energy (DOE).

2. How does CBECS affect Standard 90.1?

SSPC 90.1 uses CBECS data for a variety of purposes, including as an important data source for the standard’s Progress Indicator. The Progress Indicator measures the reduction in energy use from one edition of Standard 90.1 to the next one, such as between the 2016 edition and the 2019 edition. Pacific Northwest National Laboratory (PNNL) uses the Progress Indicator methodology to track the national impact of Standard 90.1 throughout the three-year development cycle and periodically reports the results to SSPC 90.1.

The PI applies the requirements of two different editions of the standard—the new edition compared to the previous—to a suite of established prototype energy models,¹ including 16 building types in the 16 ASHRAE climate zones found in the U.S. The savings are computed and the results aggregated across building types and climate zones using weighting factors based on new-building permit data to provide a single national savings number. The characteristics of buildings in CBECS inform the configuration of the prototype buildings for areas such as building form, heating sources, HVAC system types, wall construction and window-to-wall area.

The DOE is required by federal law (the Energy Conservation and Production Act [ECPA], as amended) to issue a determination whether the latest edition of Standard 90.1 will improve energy efficiency in commercial buildings. DOE has 12 months to publish its determination in the Federal Register, triggered by each new edition of the standard. The same federal law then provides states two years from the publication of the determination to review and update their energy code, including demonstration that the state code meets or exceeds the provisions of the updated edition of Standard 90.1 (in this case Standard 90.1-2019). PNNL builds on the Progress Indicator  approach to provide the analysis that serves as the basis for the determination.

 In addition to the Progress indicator and the DOE determination, CBECS and other data sources—such as Dodge Data and Analytics’ Construction Data—are used to determine the economic justification for new proposals to make sure they are cost-effective.

3. What is the process for quantifying the energy reduction impact of the most recent versions of Standard 90.1 with this data?

Here is a brief description of the process used for quantifying energy reductions between the different versions of Standard 90.1:

• Sixteen prototype buildings are chosen, representing the most common nonresidential and multifamily buildings types.
• Based on each edition of Standard 90.1 since 2004, these 16 prototypes are developed into minimally code-compliant energy simulation models for the various climate zones, as defined by ASHRAE Standard 169. There are nine different thermal zones ranging from extremely hot to arctic and three moisture regimes (dry, humid and marine) that result in 19 climate zones—16 of which are represented in the U.S.
• Energy simulations are run for all the various combinations of prototype buildings and climates, and the results are weighted by the relative square footage of new construction (determined from Dodge Data and Analytics’ Construction Data) ² to estimate the difference between the aggregated national energy use in the two editions of the standard.

4. What do ASHRAE members need to know about this topic?

CBECS is a very rich information source for existing building construction and equipment. It can provide information on topics such as:

• What is the typical space heating or water heating fuel for retail stores in the Southeast versus the Midwest?
• What is the typical wall insulation level for hotel/motels in the Midwest?
• What percentage of the commercial building stock was built before 1960 in a particular region?
• What is the average square footage of a restaurant or a supermarket?
• What types of HVAC systems are used in various building types in different regions of the country?
• What is the energy use of various building types in different regions of the country?

This is important information for many different types of planning and forecasting.

And the data is free and is provided by the U.S. government for anyone that wants to use it.

References

1. DOE. 2020. “Commercial Prototype Building Models.” https://tinyurl.com/yy7p3jkd

2. Lei, X, JB Butzbaugh, Y Chen, J Zhang, and MI Rosenberg. 2020. Development of National New Construction Weighting Factors for the Commercial Building Prototype Analyses (2003-2018). PNNL-29787. Pacific Northwest National Laboratory, Richland, WA. https://www.pnnl.gov/main/publications/external/technical_reports/PNNL-23269.pdf