Every building project starts with expectations: comfortable spaces, reasonable energy costs, reliable equipment, easy maintenance. The problem is that these expectations often live only in the owner's head or in scattered meeting notes. When they are never written down clearly, designers make assumptions, contractors value-engineer the wrong things and nobody can say at turnover whether the building actually delivers what was wanted.
The owner's project requirements (OPR) and the basis of design (BOD) solve this. The OPR records what the owner needs. The BOD explains how the design will deliver it. Together, they are the foundation of the commissioning process and the yardstick against which design reviews, functional tests and acceptance are measured.
The owner's project requirements
The OPR is a written document describing the functional requirements of the project and the expectations of how the building will be used and operated. ASHRAE Standard 202 and ASHRAE Guideline 0 describe it as the key document of the commissioning process, and LEED makes its preparation part of the fundamental commissioning prerequisite.
The OPR belongs to the owner. The commissioning provider often facilitates workshops and drafts the document, but the owner's staff, including facility management and operations, should shape and approve it.
What an OPR should include
| Topic | Examples of content |
|---|---|
| Project background | Purpose of the building, occupants, hours, expected life |
| Space use | Occupancy types, densities, schedules, special spaces such as labs or server rooms |
| Indoor environment | Temperature and humidity ranges, ventilation, acoustics, lighting levels |
| Energy and carbon | Energy targets, carbon goals, certifications sought, metering expectations |
| Reliability | Redundancy for critical systems, acceptable downtime, emergency power |
| Operations and maintenance | Staff skills, preferred equipment types, access, spare parts, BAS platform |
| Codes and standards | Owner standards beyond code minimums, such as health care or institutional standards |
| Budget and schedule | Constraints that affect system choices |
| Training and documentation | Expectations for operator training, manuals and systems manual |
| Future flexibility | Expected changes in use, expansion, tenant fit-outs |
Make requirements measurable
The OPR is most useful when its requirements can be verified. Compare these examples:
- Vague: "The building should be comfortable."
- Measurable: "Office spaces shall maintain 21 to 24 C in winter and 23 to 26 C in summer during occupied hours, consistent with ASHRAE Standard 55, with relative humidity not exceeding 60%."
- Vague: "The server room must be reliable."
- Measurable: "The server room cooling shall have N+1 redundancy, with automatic changeover and alarm on failure of any unit."
Measurable requirements translate directly into design criteria and test procedures. See thermal comfort and ASHRAE Standard 55 for how comfort criteria are defined.
Keep it current
The OPR is a living document. It should be updated when the owner's needs change, such as a change in tenant, a budget revision or a new energy target, and each update should be dated and communicated to the design team.
The basis of design
The BOD is prepared by the design team. It documents the concepts, calculations, decisions and product selections used to meet the OPR, along with the codes, standards and assumptions behind them.
What a BOD should include
- Design criteria: indoor conditions, outdoor design conditions (for Canada, typically from the climatic data in the National Building Code or the applicable provincial code), ventilation rates and internal loads.
- Codes and standards: for example NBC or provincial building code, NECB 2017 or 2020, ASHRAE 62.1, CSA B52, CSA Z317.2 for health care, and any owner standards.
- System descriptions: what systems were chosen and why, such as dedicated outdoor air with radiant panels, or VAV with hot water reheat.
- Alternatives considered: options evaluated and the reasons they were rejected.
- Redundancy and reliability strategy: how critical loads are protected.
- Control strategy: a narrative of how systems are intended to operate, leading to detailed sequences of operation.
- Energy strategy: how energy targets are expected to be met, with references to energy modelling where used.
- Assumptions and limitations: occupancy, schedules, equipment loads and anything the design depends on.
The BOD should be updated at each design milestone and again at the end of construction to reflect changes made during construction.
How the OPR and BOD work together
The relationship is simple: the OPR states the "what" and the BOD explains the "how". The commissioning provider compares them during design reviews.
- Does every OPR requirement have a corresponding design response in the BOD?
- Do the BOD assumptions, such as occupancy density or operating hours, match the OPR?
- Do the drawings and specifications reflect the BOD?
When there is a mismatch, it is far cheaper to resolve on paper than after installation. For example, if the OPR calls for 24/7 operation of a laboratory wing but the BOD assumes the main air handlers shut down at night, the conflict must be resolved during design.
Using the OPR and BOD during construction and testing
During construction, proposed substitutions and value engineering should be checked against the OPR. A cheaper chiller may meet the BOD capacity but fail an OPR requirement for low noise or a particular refrigerant.
During acceptance, functional performance testing procedures are written to demonstrate that systems meet OPR and BOD requirements. A test that confirms a system "works" is not enough; it should confirm that it meets the specific criteria the owner set.
After turnover, the OPR and BOD become part of the systems manual. They help future operators understand why the building was designed the way it was, and they provide context for renovations and retro-commissioning.
Common mistakes
- Treating the OPR as paperwork. An OPR written after design is complete simply describes the design and adds no value.
- Leaving operators out. Facility staff know which equipment is hard to maintain and which controls approaches have failed before.
- Generic templates. Copying an OPR from another project produces vague requirements that guide nobody.
- A BOD that is just a code list. The BOD should explain decisions and assumptions, not only list standards.
- Never updating either document. Outdated documents lead to arguments at acceptance.
Frequently asked questions
Is an OPR needed for small projects?
A short OPR, even two or three pages, is valuable on any project with HVAC systems of moderate complexity. The effort should match the project, but writing down requirements is always worthwhile.
Who signs off on the BOD?
The design engineer of record prepares and is responsible for the BOD. The owner and commissioning provider review it for alignment with the OPR.
Key takeaways
- The OPR records what the owner needs; the BOD explains how the design delivers it.
- Write OPR requirements in measurable terms so they can be designed to and tested.
- Include operations staff and update both documents as the project evolves.
- Design reviews, substitutions and functional tests should all refer back to the OPR and BOD.
- Starting these documents at pre-design is central to effective building commissioning.
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