Test Procedures for Building Energy Simulation Tools

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DOE Technology Manager: Amir Roth
Principal Investigator: Ron Judkoff, National Renewable Energy Laboratory
-- National Renewable Energy Laboratory – Golden, CO
-- J. Neymark & Associates – Golden, CO
-- Lawrence Berkeley National Laboratory (LBNL) – Berkeley, CA
-- ASHRAE Standing Special Projects Committee 140
-- Residential Energy Services Network (RESNET)
-- International Energy Agency (IEA) – Paris, France
-- Trane Inc. – Piscataway, NJ
-- Carrier Corp. – Alexandria, VA
-- AAON – Tulsa, OK
-- Tsinghua University – Beijing, China
-- University of Strathclyde – Glasgow, United Kingdom
-- Netherlands Organization for Applied Scientific Research (TNO) – Delft, Netherlands
-- Bentley Systems – Gaithersburg, MD
-- Natural Resources Canada (NR-Can) – Ottawa, ON, Canada
-- Integrated Environmental Solutions Ltd. – Glasgow, United Kingdom
-- GARD Analytics – Arlington Heights, IL
-- De Montfort University – Leicester, United Kingdom
-- Dresden University of Technology – Dresden, Germany
-- Sendai University – Sendai, Japan
DOE Funding: $300,000 in FY18, $2,652,000 to date
Cost Share: In-kind labor by partners
Project Term: October 2016 - September 2018

Project Objective

The objective of the Building Energy Simulation Test (BESTEST) and ANSI/ASHRAE Standard 140 is to increase confidence in the use of building energy simulation programs by creating standardized and citable test procedures for validating, diagnosing, and improving the current generation of software. ASHRAE first published Standard 140 in 2001, and updates were published in 2004, 2007, and 2011. Currently, NREL is working on several additional test suites. These include (1) a test suite for the air-side modeling of common mechanical equipment configurations, (2) an update to the original NREL/International Energy Agency (IEA) BESTEST building thermal fabric test cases published in 1995, (3) a test suite for thermal exchange between the building and the ground, and (4) a test suite for multi-zone energy exchange.

The Standard 140 testing framework relies on a mix of three kinds of tests: (1) Analytical tests with closed form solutions, (2) empirical tests with results based on measured data, and (3) comparative tests with neither closed form solutions nor measured data. Comparative tests fill the gaps between analytical and empirical tests for engines that have passed the first two. Collectively, the three kinds of tests form a more robust and complete structure than any could create individually or any two could create without the third. Historically, Standard 140 has relied heavily on comparative and analytical tests because “validation-grade” empirical measurements for whole-building energy simulation have been difficult to obtain. To address this problem, DOE sponsored the development of new well-characterized highly instrumented test facilities like LBNL’s FLEXLAB (Facility for Low Energy eXperiments).

Project Impact

Building energy simulation is the basis for a number of building energy-efficiency activities including energy-efficiency standards. These activities could not take place without confidence in building energy modeling engines. ASHRAE Standard 140 is the framework for establishing this confidence in energy modeling engines and—collectively—in the energy modeling enterprise. It also serves as a living engine-neutral test suite that allows an ever-expanding and rising minimum baseline of capabilities among engines available at any given time. The ASHRAE Standard 140 suite is the primary mechanism by which engines are certified for specific purposes. The most notable example for commercial buildings is the list of software qualified for use for application for the 179D tax credit. Many other organizations reference the 179D qualified software list. For residential buildings, RESNET cites Standard 140 to qualify software for the RESNET Home Energy Rating System (HERS).

The primary target audience for ASHRAE Standard 140 is engine developers like Carrier (HAP engine) and Trane (TRACE engine). Other audiences include codes and standards agencies, energy-efficiency program administrators, and building energy modeling practitioners. Standard 140 is cited and used by other ASHRAE Standards such as the 90.1 Standard for minimal energy efficiency in commercial buildings, the International Energy Conservation Code (IECC), the International Green Conservation Code (IGCC), and the energy codes of many nations including among others Canada, China, Australia, New Zealand, Portugal, Japan, Netherlands, and the European Building Energy Performance Directive. It is also cited by on the order of 100 states and localities in the U.S.

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