Or, keep making the same mistakes. Your call.

In control theory, a feedback loop returns an output to a control device in order to provide data to inform future outputs from the control device. This practice provides more accurate control and is often specified for projects. This same concept can be applied to the design and construction of BAS but in practice, the feedback loop in the design and construction process is often not closed. The output (results) of the process are never returned to inform future outputs (projects). While controls are part of most projects, somewhere between the initial control design concepts to actual operation of feedback loop.

As noted in previous columns, we believe that advanced control algorithms are part of the solution in delivering high-performance buildings. But the nature of projects often results in an open feedback loop between design, construction, commissioning, and operations, which is one reason for ineffective use of advanced control sequences.

Two questions must be answered to determine how to close the feedback loop:
  • To whom should the feedback go?
  • What feedback is needed by each party?


Depending on the project, the answers may be different. Here are some possible responses to the two questions:

To whom should the feedback go? Feedback could be provided to the following.
  • Mechanical engineer

  • Controls integrator

  • Controls contractor

  • Programmer

  • Commissioning agent

  • Several or all of the above
What type of feedback is needed by each party? Answering this question is a bit more complex. It requires knowing what challenges were encountered during the implementation process, which parties were responsible for what tasks, and an honest assessment of why the challenges occurred. To start answering this question, we need to identify:
  • Who wrote the control sequences, as well as level amount of detail and coordination of the sequences with other parties involved;

  • Who programmed the system, as well as level amount of detail and coordination of the sequences with other parties involved;

  • The scope of the controls commissioning services provided;

  • What information and training was provided to the control system operator; and

  • Was risk and/or unknown information pushed down the process supply chain? Meaning, was insufficient information provided to the contractor?
An honest assessment of these items helps to identify lessons learned and hopefully helps to prevent repeating the same mistakes in the future. Although the complete alignment of theory and practice may never be practical or possible, there is great opportunity to help close the feedback loop for control design, construction, commissioning, and operation for BAS. If we are not willing to honestly identify current project and industry challenges, it will not be possible for the industry to fulfill the current and future needs of building occupants, owners, designers, or operators.

(Note that this month’s column is courtesy of our associate, Angela Lewis. She can be reached atangela@buildingintelligencegroup.com.)ES