Air duct inspection: what we actually look for

A duct inspection is one of the cheaper services we offer and one of the most useful for diagnosing comfort problems. If your AC runs fine but some rooms never get cool, or your bills are higher than they should be, the answer is usually in the ducts.

What we look at

A proper duct inspection covers:

• Plenum connections at the air handler (these leak more than anywhere else)
• Trunk line condition and sealing
• Branch takeoffs from the trunk
• Flex duct runs for kinks, sags, and crushed sections
• Register boots and connections at each room
• Return air pickup size and location
• Visible insulation condition on supply ducts

We also measure static pressure across the air handler. If the system is fighting high static, the ducts are restricting airflow somewhere, and the inspection finds where.

What the findings usually show

About 70% of older duct systems we inspect have measurable leakage — typically 15-30% of conditioned air being lost into the attic. Common findings:

• Plenum tape that’s let go (almost universal in 20+ year old systems)
• Disconnected flex runs (sometimes blown off by service techs and never re-secured)
• Crushed flex against trusses or storage
• Original boots that have rusted out at the seam

A sealing pass typically costs 1,200-2,500 dollars and recovers most of the lost capacity. For homeowners considering AC replacement, doing the ducts first often means a smaller (and cheaper) replacement system works fine. See more on air duct inspection and how it pairs with AC repair findings.