When considering the performance of your HVAC system, pay close attention to indicators of inefficiency. Do you have:
- Indoor air quality (IAQ) issues?
- Occupant discomfort and complaints?
- Visible cracks and leaks in the ductwork?
- Inefficient fans or chillers that are working too hard?
The common reaction to these problems is to get new equipment. However, upgrades won’t remedy the issues if your ductwork is leaking.
Perform an inspection of the duct system and utilize new technologies to get the most out of your HVAC system.
Impact on Energy Efficiency
Duct leakage in commercial buildings is estimated to be anywhere from 15-40% of cubic feet per minute (CFM). A leaky system uses 25-35% more fan power than a tight system, according to the Lawrence Berkeley National Laboratory report Rationale for Measuring Duct Leakage in Large Commercial Buildings.
“In terms of energy consumption in buildings, HVAC is now the biggest piece of the pie at 39%,” says Frank Forrest, efficient solutions products manager at manufacturer Carlisle HVAC. “When you consider such significant loss on such a heavily consuming piece, it really points out the importance of having an efficient system.”
A common solution is to put new chillers on the building or different drivers on the supply fan to speed it up, Forrest says. The duct system typically gets left out but should be evaluated annually.
“Look at the ductwork first, find out how much leakage you have, and work from there. You may find that new equipment is unnecessary,” Forrest suggests. “Once the duct system is cleaned and sealed, you can more easily consider other components. It’s a trickle-down effect.”
Most don’t even realize the significance of duct leakage or that they should be paying attention to it, agrees Steven G. Liescheidt, president of engineering and consulting firm SPPECSS Consulting, LLC.
“The arguments was that duct systems don’t need sealing because the leakage rate is not that great,” he explains. “It may be time to rethink this old paradigm in light of several ASHRAE requirements.”