The ductwork is the delivery system for everything your heating and cooling equipment produces, and in many Central Texas homes it runs through the attic, one of the hottest places on the property in summer. Leaks, crushed runs and poor design can quietly waste a significant share of the cooling you pay for, and they're a common cause of rooms that never feel right. This page explains common duct and indoor air quality problems and what a licensed contractor can do about them. Requests submitted here go to an independent HVAC contractor licensed by the Texas Department of Licensing and Regulation (TDLR). We are a referral service and do not perform the work.
Signs of duct problems
- Some rooms are always hotter or colder than others, especially rooms far from the air handler or over the garage.
- Weak airflow from certain vents even with a clean filter.
- Dust builds up quickly or the house feels stuffy.
- High electric bills that don't match how you use the system.
- Visible damage in the attic: disconnected or sagging flex duct, torn insulation jackets, ducts crushed under stored items, or gaps at boots and plenums.
- Whistling or rattling at registers or returns, which can mean undersized ducts or too little return air.
- Musty smells when the system starts.
Why attic ducts matter so much here
ENERGY STAR estimates that in a typical house about 20 to 30 percent of the air moving through the duct system is lost to leaks, holes and poorly connected ducts. When ducts are in a hot attic, every leak on the supply side dumps cooled air into the attic, and every leak on the return side pulls superheated, dusty attic air into the system. Combined with the region's long cooling season (the National Weather Service's 1991–2020 normal August high at Austin's Camp Mabry is 97.8°F), duct losses can add up.
What duct work can involve
A licensed contractor might recommend one or more of these after an inspection:
- Duct sealing. Sealing joints, seams and connections with mastic or approved tape, especially at the plenum, takeoffs and register boots.
- Repairs. Reconnecting fallen runs, replacing damaged or crushed sections, and re-hanging sagging flex duct so it isn't kinked.
- Insulation. Replacing torn or deteriorated duct insulation.
- Return air improvements. Many homes have too little return air, which starves the system and can cause noise, poor comfort and pressure problems between rooms.
- Balancing. Adjusting dampers or modifying runs so airflow matches each room's needs.
- Full replacement. On older systems with brittle, leaky or poorly designed ducts, replacement is sometimes the best option, especially during an equipment replacement. ACCA's Manual D is the standard method for designing residential duct systems.
- Duct leakage testing. Some contractors use a duct blaster to measure leakage before and after sealing, so you can see the improvement.
Indoor air quality options
"Indoor air quality" covers a lot of products. Some are well supported, and some are marketed with more promise than evidence. Here's how to think about the main categories.
Filtration
The air filter is the foundation. Higher MERV ratings capture finer particles, but a restrictive filter in a system not designed for it can reduce airflow. A media filter cabinet, a deeper filter housing at the air handler, can allow higher filtration with less restriction. If you have allergies or asthma, ask the contractor whether your system can support a higher MERV filter.
Humidity control
Central Texas summers can be humid, especially in the eastern part of this service area. An air conditioner removes moisture as it cools, but oversized systems that short cycle remove less. Options include properly sized equipment, variable-speed systems that run longer at low speed, and whole-home dehumidifiers. Indoor relative humidity in the 30 to 50 percent range is a common target for comfort and to discourage mold and dust mites.
Ventilation
Tighter homes may benefit from controlled fresh-air ventilation, such as an energy recovery ventilator (ERV), so stale air and indoor pollutants don't build up.
UV lights and air cleaners
UV lamps aimed at the indoor coil can help limit microbial growth on the coil surface. Claims about whole-house air purification from various electronic cleaners vary widely. Ask for independent test data, and avoid devices that produce ozone. The EPA advises against using ozone generators in occupied spaces.
Duct cleaning
The EPA says duct cleaning hasn't been shown to prevent health problems, and that it may be worth considering when there's visible mold, a vermin infestation, or excessive dust and debris being released into the home. Be wary of very low-priced "whole house duct cleaning" offers. A legitimate service uses proper equipment and doesn't damage flex duct.
Questions to ask
- What did you find, and can you show me photos from the attic?
- Will you measure leakage or airflow before and after?
- Is the problem the ducts, the equipment size, or both?
- For air quality products: what problem does this solve in my house, and what evidence supports it?
Texas rules prohibit licensed contractors from misrepresenting the need for services. You're entitled to a clear explanation and to a second opinion.
Before an equipment replacement
If you're planning to replace your AC or heat pump, it's the ideal time to evaluate the ducts too. A high-efficiency system on a leaky, undersized duct system won't deliver its rated performance. See our installation guide.
How a request works
- Choose "Ductwork / air quality" on the form and describe the symptoms, such as hot rooms, dust, humidity or noise.
- We forward the request to an independent, licensed and insured contractor that serves your area.
- The contractor contacts you to inspect and quote. Any agreement for work is between you and the contractor.
We don't charge homeowners and don't set prices.
Ductwork Repair, Replacement & Sealing FAQs
Why is one room always hot?
Common causes include a crushed or disconnected duct, an undersized duct run, a missing return path, or a room with heavy sun exposure. A contractor can measure airflow to find the cause.
Are flex ducts in the attic a problem?
Flex duct is common and fine when installed correctly. Problems come from sagging, kinks, tears, overly long runs, and poorly sealed connections.
Should I replace ducts when I replace my AC?
If the ducts are old, leaky or undersized, it's often the best time. A new system can't perform well on bad ducts. Ask the contractor to inspect them and measure static pressure.
Do sweating ducts mean something is wrong?
Condensation on ducts in a humid attic usually points to missing or damaged insulation or air leaks. It can lead to stains and mold, so get it addressed.
Does duct sealing help?
Sealing leaks, especially on return ducts in the attic, can improve comfort and keep hot, dusty attic air out of the system.