ASHRAE Standard 229

ASHRAE Standard 229P Implementation Overview. (Image courtesy of U.S. Department of Energy)

ASHRAE Standard 229P, currently in the proposed stage, focuses on improving the accuracy and consistency of performance calculations in building projects that utilize ruleset-based methods for code compliance or beyond-code applications. The standard proposes an automated project testing framework that can verify implementations of rulesets (such as ASHRAE 90.1, Appendix G and other modeling rulesets).

Approach

Past efforts to test rule implementation in compliance software have utilized a "software testing" approach where specific software tools are certified by a process of running a large number of test cases to ensure that baseline models are created properly. This approach has been used for California's Title 24, state of Florida energy code, and by RESNET.

Standard 229 proposes a different approach where the ruleset implementation is tested for each project. This approach would allow more software tools to be used, including tools where software users manually generate baseline models. This "project testing approach" consists of two main components, the Ruleset Model Description (RMD) and the Ruleset Checking Tool (RCT), described below.

Ruleset Model Description (RMD) Schema

The RMD is a description of the building's design at the same level of detail as the "ruleset," e.g. using similar level of detail as an energy code' performance path language such as ASHRAE 90.1, Appendix G. It is not the same level of detail as a BEM software tool which typically requires additional details as modeling inputs.

The RMD schema was designed to be ruleset agnostic. I.e., it is not based around a specific energy code, but it is intended to be flexible enough to be used for many different energy codes with their own unique modeling rulesets.

BEM software vendors who utilize the standard 229 procedures must export a file following the RMD schema specifications. This requires the software to translate inputs from its internal data model to meet the RMD schema specifications.

Because the RMD schema is a higher-level model description, it is not intended to allow BEM tools import the RMD files to create a model from scratch.

Ruleset Checking Tool (RCT)

The RCT is an open source tool that reviews the proposed and baseline RMD files, compares these models to a set of rules that specify the energy code's performance path (the "ruleset") and verifies that the models meet the ruleset requirements.

Adoption and Compliance

If the standard is adopted, the following actions are needed by various stakeholders:

• Authority Having Jurisdiction (AHJ) adopts the standard, and requires projects following the performance path to use software tools that have RMD generation capabilities. When projects are submitted, they will use the RCT to verify that the RMD files represent proper implementation of the ruleset.
• Modelers do not necessarily need to do anything differently other than ensure that their modeling tool is capable of generating RMD files. They may chose to run the RCT before submitting projects to identify any issues.
• Software vendors would need to develop the capability to export RMD files, following the requirements in the standard. Standard 229P includes a set of RMD tests to verify the capabilities work properly. Software vendors do not need to implement ruleset automation, however may choose to do this as a user-friendly feature.

Additional Resources

• ASHRAE Standard 229P Development - US Department of Energy project page describing its support of the standard development.
• ASHRAE 229 Committee - ASHRAE's web page on committee activities.