Air goes into old ducts, but money leaks out

When it comes to customer comfort, it’s important to identify the whole problem before creating a solution. For many replacement equipment projects, this means repairing and replacing the existing duct system should be part of the overall solution.

No one expects homeowners to water their lawns with hoses that have holes in them — that would mean they were wasting water and paying extra money to do it. The obvious solution is to fix it, and, if it can’t be fixed, to replace it.

That goes for leaky or poorly installed ductwork, too.

“If the leaky ducts are in an unconditioned space, there is a substantial amount of energy wasted,” said John Boylan, general manager of an HVAC service company in Brighton, Michigan. “I’ve seen almost 40% energy loss in home that we’ve tested, especially during extreme winter weather.

But unlike leaky hoses, bad ductwork isn’t as obvious.

“A common misconception is that a new, high-efficiency system will solve all comfort issues,” said Michael Hartman, an HVAC contractor in Silver Spring, Maryland. “Not true.”

In fact, it doesn’t matter what the efficiency rating on the equipment is, according to David Richardson, curriculum developer and instructor at National Comfort Institute Inc.

“If the ducts are not sealed, the equipment will never operate at its rated efficiency in the field,” he said. Unfortunately, many contractors give little consideration as to whether or not the original duct design ever worked in the first place.

“They assume the duct system that’s installed works and then attach the new equipment right back to it,” Richardson said.

But the good news is, there’s an easy solution. Contractors simply need to start viewing the ductwork and the HVAC equipment as one cohesive unit. From there, it’s all about asking questions and taking measurements.

“Our technicians are trained to ask the customer if there are any areas in the house that are cold in the winter and warm in the summer,” Hartman said. “The customer knows their home better than anyone — they’ll lead you down the path to find their pain.”

However, the onus still falls on the contractor to properly diagnose the issue.

“There are often visual indicators, like clumps of dust and dirt at the duct connections where the leakage occurs,” said Boylan.

And that’s a great place to start, according to Eric George of the Building Performance Group. “In addition to a visual inspection of the duct system at each joint and connection, a quick and simple qualitative way to test leaking is by depressurizing the house to -50 Pascals with a blower-door system and placing a pressure pan over each supply and return opening,” he said.

Another way to identify airflow issues is by measuring total external static pressure (TESP). “That’s akin to a doctor taking a person’s blood pressure,” said Hartman. “There’s an inverse relationship between static pressure and airflow — the higher the static pressure, the lower the airflow.”

Chances are, technicians are going to find an airflow issue when performing these tests. And that’s because most systems are already operating under high static pressure due to undersized ducts, according to Boylan.

“Especially in older homes that were built originally to only have central heating,” George added. This means that contractors can expand their services, start offering ductwork as part of their expertise, and increase their revenue on every system replacement job.

“It increases sales and brings in a new type of work that isn’t weather-driven,” Richardson said. “It changes the game from replacing equipment only.”

Since this component of the system has often been overlooked, there may be some pushback from homeowners — wondering why none of the other companies that quoted them said anything about ductwork. That is an opportunity, and it’s knocking. Open the door by educating them. Explain things in terms they can understand.

“When we talk to our customer directly about it, we tell them that the system is moving air to and from places you don’t want it to, such as attics, crawlspaces, and interior building cavities, which can cause temperature and pressure imbalances inside the house and can contribute to indoor air quality issues as well,” George said.

Additionally, if the home is in a cold climate and the ducts are in an attic, you can also create ice dams on the roof, said Boylan.

It is for those reasons that Hartman encourages clients with duct deficiencies to spend money on duct modifications instead of higher-efficiency equipment.

“As long as the ductwork is sized appropriately, then you should have options on how to seal it,” George said. “If it’s all inside an attic space or basement that is accessible (unfinished), then it’s relatively easy to locate the leaky connections and seal them with duct mastic, silicone, and/or UL-rated metal tape.”

If leaks are located within wall or other building cavities, it may not be possible to fix the issue without removing drywall first. In these cases, another option is to inject the ducts with a chemical that can seal them from the inside out.

“This is good for sealing up ‘panned-in returns,’ which are basically floor and wall cavities being used for return ducts, where most leakage occurs,” George said. “The caveat to this sealing method is it won’t seal up gaps or holes bigger than half an inch or so, and if the duct system was undersized to begin with, sealing it up can cause the total static pressure to rise significantly and potentially damage the HVAC system.”

What it comes down to in the end is that contractors who replace systems without evaluating the ductwork aren’t giving their customers the value they paid for.

“There is definitely an opportunity in our industry for ductwork renovation and sealing,” said Boylan. “There is also a very real investment in time and money to educate your team and build the processes to make testing ductwork a part of your system.”

What to do

The industry is making strides to raise awareness and provide training resources. The notion that change is the only constant holds true here, which means it’s imperative for contractors to continually evolve along with the industry. The days of servicing HVAC equipment as a standalone unit are long gone. It’s time for every contractor to reevaluate the way they look at the system, start asking questions to pinpoint the issue, and perform the tests and measurements needed to verify the solution.

“The weak point is putting it into application,” Richardson said. “We get comfortable talking the talk. It’s a little more uncomfortable to walk the walk. When you do, you have to address that grandad’s duct sizing rules and what you’ve done for decades doesn’t always work.”