Ductwork, airflow, and humidity in Tampa, FL
Rooms that never cool, a damp house at 75 °F, a system that runs all day: contractors who test ducts and airflow before selling equipment.
Many of the "my AC is not big enough" calls around the bay turn out to be duct calls. Ducts in a vented attic that hits 130 °F in July leak conditioned air out and pull attic air in; a house with one return in the hallway starves the bedrooms; a system oversized for the house cools the air and leaves the humidity. The fix is measured on the air side, not by the size of the condenser.
Ask for a contractor who does duct work as well as change-outs, and ask for the tests before the quote.
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What the housing does to the air side
- Retrofit central air in 1920s–50s houses (Hyde Park, Seminole Heights, Kenwood, Old Northeast): ducts added where they fit, one small return, an air handler in a closet. The rooms at the end of the run never cool.
- 1970s–90s block houses (Brandon, Carrollwood, Pinellas Park, Largo): shallow attics, flex duct that has sagged and kinked, connections that were taped twice. Two or three condensers have been replaced on the same ducts.
- 1990s–2010s subdivisions (New Tampa, Riverview): ducts in a vented attic, a second floor that runs ten degrees warmer, a single zone doing two jobs.
- Flat-roof additions and Florida rooms (St. Petersburg, Largo): a duct that was never sized for the room, or none at all.
Humidity is the Florida problem
A July dew point of 73 °F means the air carries water all day. A properly sized system runs long enough to wring it out; an oversized one hits the setpoint in ten minutes and leaves the house at 75 °F and damp, which is why a house can feel worse after a "bigger" system. The remedies are sizing from a load calculation, longer run times, sealed ducts so attic air stops coming in, and, where the house still cannot keep up, a whole-house dehumidifier on the return. Florida's energy code sizes equipment by Manual J and Manual S for exactly this reason.
What the visit should include
- Static pressure at the air handler and airflow at the registers; a duct leakage test if the ducts are suspect (the energy code requires one on new duct systems).
- A look in the attic: disconnected runs, crushed flex, missing insulation, returns pulling from the attic.
- A written scope: seal, repair, add returns, or replace the ducts; the permit if the ducts are replaced (a mechanical permit, same as a change-out).
- Indoor air quality without the sales pitch: a better filter and a sealed return do more than most add-ons; UV lights and "air purifiers" are an option, not a fix for leaking ducts.