Retro-commissioning federal buildings for Canada's largest owner of office space to improve system operation and equipment performance

Public Works and Government Services Canada (PWGSC) is the department of the federal government responsible for internal servicing and administration. PWGSC is the largest owner and manager of office space in the country, providing safe, productive and energy-efficient work environments for federal employees across Canada.

"Retro-commissioning is really a kind of detective work. You start knowing very little about the equipment and systems in the building, then you search for clues, collect the evidence, and do the analysis to test your theory of what is wrong."

--Alvaro Sandrin, Prism Engineering


Among PWGSC's British Columbia real estate holdings in 2006 were several buildings whose mechanical, electrical and controls systems were not performing optimally due to various factors, including age and operating procedures. To deal with the issues of energy efficiency and occupant comfort, Prism was hired to make an assessment of each building's suitability for "retro-commissioning" (i.e., attempting to reduce energy use through the identification and implementation of low-cost operational and maintenance changes to mechanical, electrical and controls systems).


At the outset, Prism developed a "retro-commissioning test plan" to verify the buildings' current heating, ventilation and air conditioning (HVAC) system control sequences. Actual measurements of temperature and flow values were used to determine the extent to which the sequences and controls were meeting the performance requirements for which they were originally designed. Prism then made recommendations for improvements to HVAC system control sequences using on-site documents, DDC (direct digital control) configuration files, trend logs and sequences of control.

Next, Prism established a checklist of on-site measurements, control devices and related settings to act as an operating manual for the various systems. The services of a balancing contractor were used to spot-check accuracy.

The retro-commissioning process also identified numerous operational issues that had developed over time, including:

  • obsolete programming, variables and schedules left in place, resulting in confusion for the operator
  • mislabelled points and point wiring issues
  • defective and "out of calibration" sensors
  • convoluted control sequences and poorly tuned control loops
  • unclear and erroneous graphic screens
  • lack of proper trend logs
  • malfunctioning mechanical components, such as stuck dampers and leaking coil valves


Benefits of the retro-commissioning conducted by Prism for PWGSC included the following:

  • significant energy savings
  • improved system operation and equipment performance
  • improved occupant comfort
  • better indoor environmental quality
  • increased expertise of maintenance and operations staff
  • improved building documentation
  • increased asset value