Here is a conversation we have every summer. A homeowner tells us the master bedroom never gets below 80 while the living room is comfortable, so they are thinking about a bigger air conditioner. We go up in the attic or onto the roof, and the air conditioner is fine. The duct feeding that bedroom has pulled apart at a joint, and a good share of the cold air that room was supposed to get has been cooling the attic for years.
Ductwork is the part of the system nobody sees, and in Tucson it is the part most likely to be the real problem.
Why Tucson ducts fail
Most ducts here run through attics that reach 140 degrees or more in summer, or across roofs in the case of package units. Heat dries out the mastic and tape at the joints, flex duct sags and kinks, and the outer jacket cracks and lets the insulation fall away. Older homes often have undersized ducts that were marginal when they were installed and have been losing capacity ever since.
Add in the fact that a great many Tucson homes were built with ducts run as an afterthought, with long runs to the far bedrooms and sharp turns to get around framing, and it is no surprise that airflow is uneven.
The signs it is the ducts
- One or two rooms are always warmer than the rest, and adjusting the dampers or thermostat does not change it.
- Airflow at the vents is weak in some rooms and strong in others, even with a clean filter.
- Dust builds up fast inside the house. Leaky return ducts pull unfiltered attic air into the system.
- The system runs constantly on hot days but the house never quite catches up.
- Your electric bill is high for the size of the house and the age of the system.
- The attic is noticeably cool near the ductwork, which means your conditioned air is escaping into it.
If several of those sound familiar, the air conditioner is probably doing its job. The delivery system is not.
What a bigger unit would actually do
Putting a larger system on undersized or leaky ducts makes things worse. The blower pushes more air against the same restriction, static pressure climbs, the system gets louder, and the extra capacity still never reaches the hot room. Oversized systems also short-cycle, which is hard on the compressor and leaves the house humid during monsoon season. We will not size a replacement without looking at the ducts first, because the ducts often decide whether a replacement is even the right move.
What a duct inspection involves
We measure static pressure at the air handler to see how hard the system is working against the ductwork. We measure airflow at the registers to find which runs are underperforming. Then we physically inspect the ducts for disconnected joints, crushed sections, missing insulation and undersized runs. The problem is usually obvious once someone actually looks.
The fixes, from small to large
- Sealing. Reconnecting separated joints and sealing seams with mastic recovers a surprising amount of capacity for a modest cost. This is the most common fix.
- Repairing damaged sections. Replacing crushed or torn flex duct on a single run often solves a single hot room.
- Balancing. Adjusting dampers so the far rooms get their share of the air.
- Adding or resizing runs. When a room was never given enough duct to begin with, the answer is a properly sized run, not a bigger fan.
- Replacing the duct system. On some older homes the ducts are beyond sealing. A full replacement is a bigger job, but it is what lets a new system finally perform as rated.
Before you replace your AC
If you are getting replacement quotes and nobody has mentioned your ductwork, ask why. A duct inspection is part of every replacement estimate we do, because a new system on bad ducts is money spent on the wrong problem. Sometimes we find the existing system has years of life left once the ducts are fixed.
To find out why that one room never cools, schedule a diagnostic visit or call (520) 261-3909. We will tell you whether it is the ducts, the equipment, or both, and quote the fix at a flat rate before any work starts. Read more about our ductwork and airflow services.