Featured image

Commissioning is Key to Understanding Retro-Commissioning

Originally published
Originally published: 1/8/2021

Buildings evolve over time and, in today’s COVID-19 environment, retro-commissioning is more important than ever.


It was Dr. Albert Einstein who said, “if you can’t explain it simply, you don’t understand it well enough.” With this in mind, let us try to demystify HVACR retro-commissioning.

Commissioning and recommissioning other computer building systems — such as fire protection and alarms, emergency power and electrical systems — can and should follow a similar protocol. None of these systems will be discussed, other than to maintain that any other life safety devices that integrate with HVACR systems require special attention.

To understand retro-commissioning, let’s review commissioning on a new project.

Mr. Jones has purchased a property to build a new office building for his expanding business. Mr. Jones then hires an architect and relies on the architect to contract out the mechanical, electrical and plumbing engineering. The engineer designs an HVACR system consisting of:

  • Gas-fired, packaged rooftop units with a BACnet interface.
  • Variable Air Volume (VAV) boxes with electric heating coils to create zone controls.
  • A sheet metal duct system for air distribution.
  • A Digital Controls (DDC) System to regulate VAV boxes and integrate the needs of various zones and communicate with the rooftop equipment.

Fast forward a year and the complex construction project has moved along. A vacant lot has now transformed into an elegant piece of architecture that Mr. Jones can happily move his entire office staff into.

Wait. Not so fast

Yes, the building looks terrific, however, without indoor comfort and ventilation Mr. Jones’s feelings of pride and joy could easily turn into frustration and anger, eventually leaving him no alternative but to call his cousin Mr. Smith of Smith, Brown and Green Legal Firm to begin an endless process of litigation.


Let’s pull back the curtain and see how to avoid the process.

Before turning the building over to Mr. Jones, the HVACR contractor sent his start-up technicians to the job site. They carefully followed the manufacturer’s instructions and checked each function of the rooftop equipment, including heating, cooling, ventilation modes, safety and operating controls, belts, filters, direction of rotation all checked and verified and documented.

Now, it was time for the control department to get in there. All VAV boxes checked, as is the position of outside air dampers, economizer section operation, duct pressure controls, etc.

Before the mechanical contractor leaves the project as directed by contract, he hires an independent third-party balancing contractor to verify all air flows meet the engineer’s requirements.

The contractor has now finished his work … well, almost. Before the project started, Mr. Jones and the architect made the decision to employ the services of a third-party commissioning agent to assure Mr. Jones the entire HVACR system has been installed as required in the contract.

Each MEP engineer more than likely will have their own version of what this process should include. Generally, the process could follow this scope:

  • Validate that each piece of equipment is installed in accordance with plan specifications and approved submittals.
  • Field verify all equipment installed complies with plans, specifications and approved submittals.
  • Carefully document all data.
  • Validate and check all HVACR infrastructure including piping and ductwork.
  • Checking and assuring such things as pipe and duct supports, sizing accuracy, duct joints, insulation, vibration elimination devices, condensate drains and traps (this list can be expansive).
  • Review and validate all HVACR contractor documentation pertaining to equipment startup to assure that manufacturing recommendations have been documented and complied with.

The commissioning agent must now go to work with the control installation personnel to assure all sensors are properly tagged and calibrated. The agent will also put the systems through all aspects of the sequence of operation.

This part of the process is often the most difficult and important as it will expose any issues pertaining to the integration and communication of various technologies. Any mistakes on the engineering, programming or possibly architectural changes that were missed will now surface and can be corrected.

Some important notes

For the commissioning process to be successful it is vital that the engineer, contractor and commissioning agent establish a working relationship as soon as possible. With good communication, trust and respect there should be few surprises and the commissioning process will be smooth and seamless.

In many projects the design team may have opted to bring on an HVACR contractor early in the process to fulfill both engineering and installment roles. While this method may require some structural changes, it should not eliminate this vital commissioning process.

The owner, architect and design build firm should agree that either the contractor or a third party will be used for commissioning. It still remains essential that the process be performed.


Now that we are all on the same page and can agree on the basic requirements of commissioning, let’s discuss “retro-commissioning.” What are the benefits to building owners for commissioning an occupied building?

The commissioning of a new building as discussed above has several benefits:

  • It assures the owner he got what he paid for.
  • It assures the owner his building is operating at full efficiency and reduced operating costs.
  • It assures the owner that occupants are receiving the proper ventilation.

Let’s go forward and see what happens down the road. I think it’s reasonable to assume that a large percentage of existing buildings have never been commissioned (I know of no valid statistics on the subject).

Now, let’s compound the problem as time goes on … more likely than not a building evolves and changes.

  • Partitions are moved
  • HVACR units are replaced
  • Occupancy density may increase or decrease
  • Lighting wattage may be upgraded to L.E.D. significantly reducing HVACR requirements
  • Computer loads may vary
  • Branch ducts may be disconnected from air outlets
  • Outside air dampers may no longer operate as intended
  • Exhaust fans may not be on an occupancy schedule
  • The controls system may be obsolete or worse, not functioning

Retro-commissioning will resolve these issues by following a protocol as described in the commissioning process. The final result will be:

  • Reduced operating costs
  • Extended life of HVACR equipment
  • Better comfort
  • Better air quality for occupants
  • Minimize or eliminate the use of building in-house staff to monitor HVACR issues.

If that is not enough in today’s world, I don’t know what is.

Over time, many buildings properly commissioned and maintained may still suffer from the same ailments as buildings never commissioned.

Why It’s Important

In today’s COVID-19 environment, retro-commissioning a building is more important than ever. Buildings that have been commissioned previously have the advantage of a strong documentation trail.

As to who is best to retro-commission a building? There are firms that specialize in this process, many engineering firms are also engaged in doing retro-commissioning as are HVACR service companies.

Many existing buildings have already had lighting upgraded to L.E.D. lighting, in those cases it is likely that HVACR has not been modified to accommodate this modification. If so, this is an enormous opportunity for the retro-commissioning provider to further reduce building energy costs by reconfiguring the HVACR system to accommodate the lower wattage requirements of the lighting with the added benefits of decreasing summertime space relative humidity.

If no lighting upgrade has been done then now is the time.

Assuring proper air ventilation, possibly adding better filtration and other air cleaning devices must also be presented to building management.

Finally, and perhaps most important, this process will be kinder to the environment and contribute to the health and well-being of our planet.


More Articles

article image

Commissioning is Key to Understanding Retro-Commissioning

Buildings evolve over time and, in today’s COVID-19 environment, retro-commissioning is more important than ever.