A performance specification describes the ultimate function to be achieved, leaving the means and method up to the contractor.
Example: Provide foundation perimeter insulation having a k = .20 @ 75 degrees F, and a minimum compressive strength of 20 lb/ft.
A procedure specification describes the material to be used and its physical relationship to the surrounding construction. It should detail the qualities, properties, composition, and assembly.
Example: Provide extruded closed-cell polystyrene board as manufactured by XYZ Corp., 2” thick × 24” wide.
Application. There is nothing inherently “wrong” with either type of specification. Performance specs, for example, may shift responsibility for the design onto the contractor, but they also increase the contractor’s options and control.
Performance specifications may be used more often in descriptions of mechanical and electrical equipment, but they will even be used for things like concrete (minimum compressive strength of 3000 psi @ 28 days).
Procedure specifications must be correct in every respect in order to avoid problems. If it is properly followed, the risk of its design success will remain with the designer.
If a procedure and a performance specification are provided for the same item, the contractor is fulfilling its obligation by providing the exact material described. There is no further duty to confirm that the described material also meets the performance description—that was up to the designer in the first place.
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