Five Signs Your Ductwork Needs Replacing, Not Just Cleaning

The ducts are over 15 years old

Flex duct, the silver-jacketed tubing used in most residential HVAC systems in Texas, has a practical lifespan of about 15 to 20 years. The inner liner degrades, the insulation compresses, and the vapor barrier cracks. Rigid metal duct lasts longer, but the joints and seals do not, and corrosion in humid attic environments is cumulative.

Age alone is not a reason to replace ductwork, but it sets the context for everything else on this list. A 20-year-old duct system showing one of the problems below is probably showing all of them, and patching individual sections is temporary when the material itself is at the end of its useful life.

Rooms that will not cool evenly

If certain rooms are consistently warmer than the rest of the house and adjusting the thermostat does not fix it, the ductwork serving those rooms is the first place to look. Common causes include a flex duct run that has kinked where it crosses a truss, a section that has pulled free from its collar at the trunk line, or a run that is too long and too narrow for the room it serves.

In The Woodlands, where most duct systems run through attics that hit 150 degrees in July, a poorly insulated run also bleeds heat into the cooled air on its way to the room. A 30-foot duct run through an R-4 insulated flex duct in a 150-degree attic can lose 10 to 15 degrees of cooling before the air reaches the register.

Dust that never stops, no matter how often you clean

If you notice dust accumulating on furniture within a day or two of cleaning, and especially if you see dust streaks or discoloration around your supply registers, the ductwork has leaks pulling air from the attic. Attic air is full of insulation fibers, dust, and whatever the wind carries in through soffit vents. When a duct joint separates or the inner liner tears, the blower pulls that attic air into the conditioned airstream.

Duct cleaning addresses what is inside the duct. It does nothing about holes that pull contaminated air in from outside it. If the dust returns quickly after a professional cleaning, the problem is the duct envelope, not what accumulated inside it.

Your energy bills have climbed without explanation

Leaky or poorly insulated ductwork can waste 20 to 30 percent of the conditioned air the system produces. That air, which you paid to cool, goes into the attic instead of the rooms. The system runs longer to compensate, which raises the electric bill and shortens the equipment's lifespan.

If your bills have risen steadily over the past two or three years while your usage patterns have stayed roughly the same, and the HVAC equipment itself has been maintained, the duct system is the next thing to investigate. A duct leakage test (a blower-door test on the duct system) measures exactly how much air is escaping and where.

Visible damage in the attic

If you can safely access your attic, look at the ductwork with a flashlight. Common problems you can see without tools:

• Flex duct sagging between supports, creating low spots where condensation collects
• Sections where the outer jacket is torn or missing, exposing the insulation
• Joints where the duct has pulled free from the metal collar or boot
• Kinks where a run crosses a truss or makes a sharp turn
• Discoloration, staining, or visible mold on the duct surface

Any one of these is repairable if the rest of the system is sound. Three or more on a system older than 15 years points toward replacement being the better investment.

What a full replacement looks like

A full duct replacement typically takes one to two days for an average-sized home. The old ductwork is removed from the attic, new runs are sized based on a room-by-room airflow calculation, and the new ducts are supported, sealed at every joint with mastic, and insulated to the current energy code. The result is balanced airflow, lower energy use, and cleaner air.

Cold Front A/C of The Woodlands (TACLA95237E) handles air duct replacement across The Woodlands, Spring, Conroe, and the surrounding area. Call (832) 559-8236 to schedule an inspection.