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Improving Energy Performance through Retro-Commissioning: "Weighing the Pig" vs. "Making it Fly"

Timothy P. Pennock, PE, GRG, Inc.

Many energy management programs are administered by staff that does not understand how the building energy consuming systems actually work. They spend a lot of time and energy "weighing the pig" on a regular basis by measuring energy consumption. A different skill set is required to actually interrogate the performance of the HVAC systems and improve operation to reduce energy performance and actually "make it fly."

Commissioning Professionals have a broad skill set which encompasses design, installation, set-up, sequences of control, operation, optimization, and maintenance of HVAC systems. These skills allow the Commissioning Professional to quickly identify hidden underperforming systems and realize immediate energy savings.

Retro-Commissioning existing laboratory building HVAC systems usually results in a minimum energy savings of 10 percent. HVAC systems in air-driven laboratories consume large amounts of energy in pre-heating, cooling, re-heating, humidification, dehumidification, and pressurization processes. Control system setpoint adjustment of just one degree in air temperature, or a few hundredths of an inch of pressure can affect energy consumption by tens of thousands of dollars per year.

We will present lessons learned from Retro-Commissioning laboratory and healthcare facilities and their economics. We will demonstrate through specific examples of common hidden system failures how a 1,000 percent payback is possible. Facility managers can use these techniques to improve the energy performance of their existing buildings.

Labs21 Connection:

There is a far greater opportunity for industry-wide energy savings in the multitude of existing lab buildings than there is in designing new buildings according to energy efficient principles. An experienced Commissioning team is one of the few resources available to laboratory facility owners who can:

  1. Reverse-engineer the design intent of the systems,
  2. Evaluate system performance based upon fundamental psychrometrics,
  3. Evaluate control system logic,
  4. Identify hidden control device failures, and
  5. Adjust setpoints immediately to save energy savings.

Four hours of Retro-Commissioning of a 60,000 cubic feet per minute university biological laboratory discovered four hidden air handling unit operational problems that resulted in over $100,000 of unexpected energy savings.

Two hours of Retro-Commissioning of a 250,000 square foot hospital facility discovered hidden failures with the pneumatic spring return open chilled water valve actuators on eight air handling units. Identifying the hidden problems with these valves had a two-fold benefit to the owner. First, they saved over $100,000 in unnecessary overcooling and reheating energy costs. And second, they were able to defer a chiller plant expansion project that was not in their capital budget for a small data center renovation because Retro-Commissioning reduced the cooling load on the chiller plant by almost 150 tons.


Tim Pennock oversees the Commissioning Services group at GRG and has 20 years of experience in the building industry, and 5 years of commissioning experience. He is responsible for commissioning over 100 projects. Tim has also provided Retro-Commissioning (CxR) Services for over 30 existing buildings. He earned a BSME and MBA, is a registered Professional Engineer in several states, is a LEED™ 2.0 Accredited Professional, a QCP™ Qualified Commissioning Process Provider, and is a Certified Commissioning Authority through ACG.


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