The Basis of Design (BOD) documents the thought processes and assumptions behind design decisions being made to meet the Owner’s Project Requirements (OPR). The OPR is intended to capture the need and expectation from the project.
CALGreen Code Section 5.410.2.2: Basis of Design (BOD). [N]
A written explanation of how the design of the building systems meets the OPR shall be completed at the design phase of the building project. The Basis of Design document shall cover the following systems:
1. Renewable energy systems.
2. Landscape irrigation systems.
3. Water reuse systems.
Intent:
The BOD establishes how the building systems will meet the OPR and outlines design assumptions not indicated in the design documents. The design team develops the BOD to describe why the systems were selected. The BOD is most effective when developed early in the project design and updated as necessary throughout the design process.
Note: See Chapter 8 of this guide for forms and templates.
Compliance Method:
Compliance is demonstrated by the completion of the BOD document and/or approving the BOD document form (see note above). The BOD should include the following, as applicable:
1. Renewable energy systems:
• Provide narrative description of system—type, performance, control type, energy savings and payback period.
• Describe reason for system selection—why chosen system is better than alternatives regarding issues such as performance, efficiency, reliability, flexibility, simplicity, expandability, cost, payback period, utility company incentives, owner preference.
• Sequence of operation—operating schedules, set points and storage capacity.
• Describe how system meets the OPR.
2. Landscape irrigation systems:
• Provide narrative description of system—type, performance and water usage.
• Describe reason for system selection—why chosen system is better than alternatives regarding issues such as performance, efficiency, reliability, flexibility, expandability, cost, owner preference, simplicity.
• Sequence of operation—operating schedules and set points.
• Describe how system meets the OPR.
3. Water reuse systems:
• Provide narrative description of system—type, performance, capacity and reuse purpose.
• Describe reason for system selection—why chosen system is better than alternatives regarding issues such as performance, efficiency, reliability, flexibility, expandability, cost, owner preference, simplicity.
• Sequence of operation—operating schedules, set points.
• Describe how system meets the OPR.
Enforcement:
Plan intake: The plan reviewer should confirm the following in the construction documents:
• The BOD is provided for every system to be commissioned with an explanation of how the design of the building systems meets the OPR and that the BOD contains the required elements listed in the code;
• Receipt of a copy of the signed BOD document; or
• Receipt of a form signed by the architect, engineer or designer of record, attesting that the BOD has been completed and meets the requirements of the OPR.
On-site enforcement: The inspector should verify that the BOD criteria as attested by the architect, engineer or designer of record are being implemented during construction.
(Excerpted from ‘Guide to the 2019 California Green Building Standards Code Nonresidential’ – Chapter 5)
