A performance specification is a document that specifies the operational requirements of a component or installation. Simply put, it tells the contractor what the final installed product must be capable of doing. The contractor is not instructed as to how to accomplish the task of meeting the performance specification requirements – only as to how the component must function after installation.
The general concept behind the performance specification is for the designer to describe what they need and the contractor to determine the best way to get there. It focuses on the outcome and shifts the selection of materials and methods, as well as a portion of the design work, onto the shoulders of the contractor. This approach can provide incentives for innovation and flexibility in the construction approach but also reduces the amount of control that the designer has over the project.