Owner's Project Requirements and Basis of Design
The Owner's Project Requirements (OPR) is a written document that captures the owner's functional needs, expectations, and performance criteria for the project. It is the yardstick against which design and performance are measured. The Basis of Design (BOD) is the designer's response - the assumptions, calculations, and system selections that satisfy the OPR. The candidate must keep these distinct: OPR is owner-authored (with CxA facilitation); BOD is design-team-authored.
A strong OPR addresses intended use and occupancy, environmental and comfort criteria, energy and sustainability goals, indoor air quality, maintainability, redundancy and reliability needs, budget and schedule constraints, and training and documentation expectations. Vague OPR language ("comfortable," "efficient") is a defect - criteria should be measurable, e.g., space temperature setpoints, ventilation rates, and target energy use intensity.
Traps in questions: (1) treating the BOD as the source of truth when the OPR governs; (2) assuming OPR is frozen - it should be updated through design and construction with documented change control; (3) missing that a gap between OPR and BOD is itself a finding the CxA must log and resolve.
Rule of thumb: every OPR criterion should be testable. If you cannot design a functional test around it, rewrite it. Worked example: OPR states "server room shall maintain 68–77°F year-round with N+1 cooling." The BOD must show cooling capacity, redundancy, and controls logic; the CxA writes a functional test that fails one cooling unit and confirms the remaining unit holds setpoint.