HVAC & Indoor Air Quality
Air duct cleaning and the East Texas humidity problem.
Why East Texas is different
Lufkin, Nacogdoches, Longview, and Kilgore — along with Houston, Polk, Jasper, Rusk, and Panola counties — sit in a humidity band that averages 70%+ outdoor relative humidity for most of the year. Your HVAC system is the single largest moving air machine in your home — and every square foot of ductwork is a surface where warm, humid air meets cold metal. That's where condensation forms, dust sticks, and microbial growth starts.
What "duct cleaning" actually means
A proper cleaning is more than vacuuming a few registers. Done to NADCA standards it includes negative-air containment, source removal with rotary brushes or air-whip tools, cleaning of the blower and evaporator coil, and sealing access ports afterward. Cheap "$99 whole-home" offers usually skip the mechanical agitation step — meaning the buildup stays put.
Signs your ductwork is the problem
- Musty smell that hits you when the AC kicks on and fades a few minutes later
- Visible dust discharge from supply vents even after filter changes
- Allergy or sinus symptoms that improve when you leave the house
- Uneven cooling — some rooms cold, others sticky and warm
- Higher-than-expected humidity readings (over 55% indoors with the AC running)
The humidity-mold connection
Mold needs three things: an organic food source (dust), a surface, and moisture. Ductwork supplies all three when humidity is uncontrolled. Cold supply runs sweat. Flex duct sags and traps condensate. Return-side leaks pull humid attic air across the coil. Clean the ducts without fixing those, and colonies re-establish within a cooling season.
The fix, in order
- Measure indoor humidity for a week. Log it morning and evening.
- Seal return-side leaks first — they drive the most moisture in.
- Verify the AC is sized correctly. Oversized units short-cycle and don't dehumidify.
- Consider a dedicated whole-home dehumidifier if you can't hold 55%.
- Then — and only then — schedule the duct cleaning.
- Change filters on a calendar, not when you remember. MERV 11 minimum for East Texas.
When to call a professional
Call immediately if you see visible mold at supply registers, smell a persistent musty odor, or have had any water event (roof leak, condensate overflow, flooded attic) that reached the HVAC system. At that point it's remediation, not maintenance.
Related guide
Mold Remediation Explained
Related episode
Mold in East Texas: Humidity, Homes, and Health
Quick answers
How often should I have my air ducts cleaned in East Texas?
For most East Texas homes, every 3-5 years is a reasonable baseline. Schedule sooner if you've had water damage, visible mold, a rodent issue, recent renovations, or a household member with allergies or respiratory issues.
Does duct cleaning actually help with mold?
Only if the underlying humidity problem is fixed at the same time. Cleaning removes surface contamination, but if your system keeps returning humid air to cold metal surfaces, mold will come back within months.
What indoor humidity should I target in East Texas?
Aim for 40-55% relative humidity year-round. Above 60% is where mold, dust mites, and musty odors take hold. A cheap hygrometer at your thermostat is the fastest way to know where you actually sit.
Is a UV light in the ductwork worth it?
UV-C lights installed near the evaporator coil can reduce microbial growth on the coil itself, but they don't replace fixing air leaks, humidity, or dirty ductwork. Treat them as one layer, not a silver bullet.
Can I just clean the vents myself?
You can vacuum registers and grilles — that helps with dust. Full duct interior cleaning requires negative-air equipment and rotary brushes to actually remove buildup rather than push it deeper into the system.