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Commissioning: Pre-Design Phase Commissioning Activities

Many industry practitioners, when asked about commissioning, will tell you it’s testing that occurs at about the same time as the final punchlist during the construction phase of a project. Although system testing is a critical component of the commissioning process and a number of so-called “commissioning” jobs have been limited to the end of construction, the greatest benefits can be realized by starting the commissioning work as early as possible. This month we’re going to outline what commissioning tasks are best performed during the pre-design, programming, or conceptual design phase of a building project.

At the same time a building owner is defining what the building should be architecturally, e.g., how many square feet, how many floors, what height between floors, what types of building materials, how many windows, etc., the owner needs to start thinking about what they want the new building’s mechanical and electrical systems to do. Some of the fundamental questions to ask include:

  • What space temperature do we want to maintain and within what tolerances or limits?

  • What space relative humidity do we want to maintain and within what tolerances or limits?

  • How much fresh air ventilation do we want to provide?

  • What are the maximum acceptable levels of indoor CO2 or VOC’s?

  • Do we want some spaces to be specially pressurized with respect to other spaces?

  • Are there minimum and/or maximum acceptable air flow rates, i.e., air changes per hour, CFM/ft2?

  • What are acceptable noise levels?

  • What equipment do we want to have on emergency or standby power?

  • Do we want to limit the type of lighting fixtures and lamps that are specified?

  • Are there specific types of systems which won’t even be considered?

  • What are our target energy consumption rates for the new or renovated building?

The questions to be asked are limited only to the owner’s priorities. What does the owner think is critical for properly functioning systems? Most of the questions will need to be asked and answered for each type of space programmed into the building, e.g., offices, conference rooms, laboratories, classrooms, operating rooms, auditoriums, mechanical spaces, toilet rooms, etc. The answers will vary from space type to space type.

By documenting the answers to these questions, the owner will be starting the building’s Design Intent Document (D.I.D.), a dynamic document which will be updated and enhanced as the design process moves into design development and construction documents. We’ll come back to the D.I.D., what it includes, and how it is used again and again in future columns.

The D.I.D. is the backbone of the commissioning process and is critical to the success of all projects. It is a written “program” which clearly defines how the systems to be commissioned are to operate in order for the building to be considered a success and “functionally complete” at the end of construction. The D.I.D. is the GOAL to which all designers and contractors should be working through all phases of the project.

The performance standards defined in the D.I.D. must be quantifiable and objectively “testable” so that at the end of construction the testing process can definitively prove that the goals have been realized. For example, a goal of having “comfortable” spaces will not suffice, because “comfortable” is a subjective, unmeasurable goal.

Once the D.I.D. is developed and frequently revisited, the design engineers have a “road map” to follow as they start designing the systems. In addition, if it is clear what performance is going to be tested at the end of construction, the designers can incorporate provisions for that testing into the system design. Examples of such provisions include flow meters, temperature sensors, pressure sensors, etc., or at least taps for utilizing temporary devices during the testing phase of commissioning.

Finally, the process of starting the D.I.D. is critical for enhancing communication between the owner and the design team. Questions must be asked and answers must be documented very clearly for everyone to review and approve prior to proceeding with the design. An excellent D.I.D. will all but eliminate the possibility of the owner saying to the designer at the end of the project, “Gee, that’s not what I wanted.”

So, start early, ask the right questions, and document, document, document.


Commissioning: Getting It Right

Engineered Systems, February, 1998

Rebecca Ellis, PE, LEED AP, CCP, CxA
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318