## 1.5 Reference Method

The reference procedures and method described in this manual establish the basis of comparison for all software. The approval process ensures that a minimum level of energy efficiency is achieved regardless of the software used. This is accomplished by:

• Specifying a series of reference method comparison tests that candidate software passed.

• Specifying input that may vary for credit, and input that are fixed or restricted.

• Defining standard report output requirements.

• Certifying the software vendor requirements in this manual.

The Nonresidential ACM Reference Manual is an approved document, separate from the formally adopted ACM regulations. This approval gives the Energy Commission flexibility to incorporate new modeling procedures or features, or fix errata, within the code cycle. The document is said to be in continuous maintenance. Software may be certified with the capability of modeling specific building systems or features.

The Energy Commission's purpose in approving additional capabilities is to accommodate new technologies which have only begun to penetrate the market and new modeling algorithms. Newly added capabilities that evaluate measures already in relatively common use shall have their standard design for the measure based on the common construction practice (or the typical base situation) for that measure since common practice is the inherent basis of the standards for all measures not explicitly regulated. For example, the Commission has no interest in an optional capability that evaluates the energy effects of dirt on windows unless a new technology produces substantial changes in this aspect of a building relative to buildings without this technology. The burden of proof that an additional capability should be approved lies with the applicant.

Companion documents that are helpful in preparing software for certification include the latest editions of the following Energy Commission publications:

• Energy Efficiency Standards

• Appliance Efficiency Regulations

• Nonresidential Compliance Manual

• ACM Approval Manual

• Reference Nonresidential Appendices

• Reference Joint Appendices

In this manual the term "standards" means the Building Energy Efficiency Standards, Title 24, Part 6 of the California Code of Regulations. The term "compliance" means that a building design in an application for a building permit complies with the "standards" and meets the requirements described for building designs therein.

There are a few special terms that are used in this manual. The Energy Commission approves software for use in demonstrating compliance. Energy Commission approval means that the Commission accepts the applicant's certification that software meets the requirements of this manual. The proponent of candidate software is referred to as a vendor. The vendor shall follow the procedure described in this document to publicly certify to the Energy Commission that the software meets the criteria in this document for:

• Accuracy and reliability when compared to the reference method.

• Suitability in terms of the accurate calculation of the correct energy budget, the generation of output for transmission to standardized forms, and documentation on how the program demonstrates compliance.

In addition to explicit technical criteria, Energy Commission approval will also depend upon the Commission's evaluation of:

• Enforceability in terms of reasonably simple, reliable, and rapid methods of verifying compliance and application of energy efficiency features modeled by the software and the inputs used to characterize those features by the software users.

• Dependability of the installation and energy savings of features modeled by the software. The Energy Commission will evaluate the probability of the measure actually being installed and remaining functional. The Commission shall also determine that the energy impacts of the features that the software is capable of modeling will be reasonably and accurately reflected in real building applications of those features. In particular, it is important that the software does not encourage the replacement of actual energy savings with theoretical energy savings due to tradeoffs allowed by the software.

For the vendor, the process of receiving approval of software includes preparing an application, working with the Energy Commission staff to answer questions from either Commission staff or the public, and providing any necessary additional information regarding the application. The application includes the four basic elements outlined below. Commission staff evaluates the software based on the completeness of the application and overall responsiveness to staff and public comment.

The four basic requirements for approval include:

1. Required capabilities.

a) Software shall have all the required input capabilities explained in Chapter 2.

b) Software shall meet software requirements and documentation requirements for applicable features supported by the software, as described in Chapter 3.

2. Accuracy of simulation.

a) The software shall demonstrate acceptable levels of accuracy by performing and passing the required certification tests discussed in Appendix 3B.

b) The software vendor conducts the specified certification tests in Appendix 3B, evaluates the results, and certifies in writing that the software passes the tests. The Energy Commission will perform spot checks and may require additional tests to verify that the proposed software is appropriate for compliance.

c) When energy analysis techniques are compared, two potential sources of discrepancies are the differences in user interpretation when entering the building specifications, and the differences in the software algorithms (mathematical models) for estimating energy use. The approval tests minimize differences in interpretation by providing explicit detailed descriptions of the test buildings that must be analyzed. For differences in the software algorithms, the Energy Commission allows algorithms that yield equivalent results.

3. User’s Manual.

The vendor shall include a user’s manual and/or help system that provides appropriate guidance for specifying inputs and running a simulation for compliance.

4. Program support.

The vendor shall provide ongoing user and enforcement agency support as described in the Nonresidential ACM Approval Manual.

The Energy Commission may hold one or more public workshops with vendor participation to allow for public review of the vendor's application. Such workshops may identify problems or discrepancies that may necessitate revisions to the application.

Commission approval of software programs is intended to provide flexibility in complying with the standards. In achieving this flexibility, however, the software shall not degrade the standards or evade the intent of the standards to achieve a particular level of energy efficiency. The vendor has the burden of proof to demonstrate the accuracy and reliability of the software relative to the reference method and to demonstrate the conformance of the software to the requirements of this manual.