Over the last decade the term duct renovation has been heard a lot in the HVAC industry. The term refers to the process of testing, diagnosing, repairing, and balancing duct systems. Typically, this service is offered to a customer when a contractor proposes to replace equipment. Let’s take a look at the process and the benefits to a homeowner and a contractor.

Contractors who offer duct renovations usually include air balance testing as a critical part of a replacement sales call. An air balancing hood and other instruments are used to test the system. This kind of testing has two primary advantages. First, it provides essential information to the homeowner, which helps them understand that replacing equipment alone won’t solve many of the comfort and efficiency issues they’ve been living with. Secondly, the information obtained from this testing pinpoints system defects. This allows the homeowner to understand the problems that are uncovered, enabling the contractor to prescribe essential repairs that will allow the new equipment to perform within the manufacturer’s specifications.


For years the primary emphasis of the HVAC industry has been to repair or replace the equipment. While this will always be the core of our business, we have discovered through testing that the real solutions to comfort, efficiency, indoor air quality (IAQ), and the other benefits we claim to deliver to our customers are found by renovating the duct system.

System performance depends on duct system performance. Equipment performance alone is critical, but is only a piece of the puzzle. Yet, by their actions, 90% of contractors assume the duct system is operating properly and don’t address it after the initial installation.

Today’s air balance testing and rating confirms that new replacement equipment often operates at only 50% of rated capacity under extreme weather conditions if it is simply “hooked up” to an existing duct system. Once you help your customers understand this fact, selling additional services is automatic.

Progressive contractors have another 5 to 7 years to enjoy little or no competition in the duct renovation market, due to the way current government and utility programs are shaping up. “Duct sealing” is a short-cut method that is supposed to double for duct renovation, but drastically misses the mark. From data we’ve gathered from completed duct sealing programs, duct sealing alone has a negative energy impact close to 50% of the time.

Duct systems are generally undersized when installed in today’s tight residential conditions. Most contractors, including those that use the out-of-the box manual D programs, usually size ducts equivalent to .10in. on a duct sizing calculator. When these duct systems are simply sealed, typical static pressures often exceed .90in. with most fans in these systems rated at a maximum total external static pressure of .50in., the result is airflow of 300 cfm per ton or less.

While most contractors always seal ducts, this step is usually postponed until the system airflow and thermal losses have been measured and evaluated. Most duct renovations include the addition of at least one major return duct to relieve excessive static pressure. Typical renovations also include the addition of several supply ducts, some duct suspensions, replacement of restrictive grilles, and providing a few other essential performance enhancing steps.

Duct renovations often include adding two or more filters to the system to reduce filter pressure drop. When the duct system is performing well and each room has required airflow, refrigerant charge and combustion efficiency can be addressed.

The real truth in the matter is that each duct system is a “living and breathing” device (although most operate like they’re suffering from asthma) so each has to be tested, diagnosed and repaired individually. Quick fixes made by slapping on a duct sealant just don’t do the job.

The business benefits of system diagnosis and duct renovations are rock solid. These benefits include:

• Build credibility with your customers by teaching them about their systems.
• Grant customers the knowledge to make their own decisions based on real time information about their system and its performance, not generic manufacturer’s information.
• Increase closing rates for salespeople and reduce the number of sales calls required to meet sales volume goals. (Closing rates often double when using test and teach selling methods)
• Increase the sale price of each changeout by 25% to 50% by including duct renovation
• Achieve 60% to 80% gross margins on a portion of your work that has little or no competition. The financial formula that accompanies duct renovation discloses a two to 10 times increase in job net profits.

Duct renovation provides a new opportunity for those who can step up to the plate and deliver the best quality systems in the industry. Embracing change can be a challenge, but it offers great rewards. While there are no quick fixes, it’s a great opportunity to deliver a better product and service, and dismiss your competition by separating yourself from the pack of box sellers.

This is a new industry inside our industry. It’s a small group, comparatively speaking, but it seems there’s always room at the top.

Rob “Doc” Falke serves the industry as president of National Comfort Institute a training company specializing in measuring, rating, improving and verifying HVAC system performance. If you're an HVAC contractor or technician interested in a duct renovation procedure, contact Doc at robf@ncihvac.com or call him at 800-633-7058. Go to NCI’s website at nationalcomfortinstitute.com for free information, technical articles and downloads.