Duct Replacement & Sealing

In most Austin-area homes, the air handler and ductwork sit in a vented attic that can top 130°F on a summer afternoon. Every leak in a supply duct pushes cooled air into that attic. Every leak in a return duct pulls hot, humid, dusty attic air into your system.

ENERGY STAR estimates that a typical home loses 20 to 30 percent of the air moving through its ducts to leaks, holes and poor connections. In an Austin summer, that shows up as long run times, a back bedroom that never cools off and humidity that will not come down.

Ducts also pick up heat through their walls. With thin, damaged or missing duct insulation, air that left the coil cold arrives at the register noticeably warmer.

Most Austin-area homes run flexible duct from a fiberglass ductboard plenum out to each room. Pulled tight, supported at proper intervals and run with gentle bends, flex performs well. Installed poorly, or left alone for years, it sags between supports, kinks around framing and gets crushed by whoever worked in the attic last.

Every sag and tight bend adds resistance and cuts airflow to that room. Attic heat makes the outer jacket brittle over time, and connections at boots and collars loosen or pull apart. Straps that pinch the duct, runs far longer than needed and ducts lying on hot attic surfaces are all problems we find and fix.

Not every duct problem needs new ducts. The deciding question is whether sealing alone will get enough air to the rooms that run hot.

• Sealing makes sense when the ducts are in reasonable shape and sized correctly. Sealing leaks at the plenums, boots, collars and connections with mastic and proper tape can cut leakage substantially, and it is usually faster and less expensive than replacement.
• Replacement makes sense when ducts are crushed, torn, deteriorated, contaminated or badly undersized, or laid out so poorly that sealing will not fix the comfort problem. It is also the time to fix design problems, such as adding a return, resizing trunks or moving registers.

Gold Eagle does both, so we can recommend whichever one fixes the room that is running hot.

If your ducts are in good shape and just dirty, air duct cleaning may be all you need.

ACCA Manual D is the industry-standard method for sizing a duct system. It uses the room-by-room loads from a Manual J calculation and the blower’s available airflow to size each trunk, branch and return so every room gets the air it needs. Many existing Central Texas homes were never designed this way.

When we replace ductwork, we design it instead of copying what was there. Good ducts also let a new high-efficiency AC or heat pump deliver the performance it is rated for. Learn more in Smart HVAC Design: Manual J, D and S Explained, and see our ductwork services and AC services.

The main things that drive the cost of duct work are:

• The size of the home and the number of supply and return runs
• Sealing only, partial replacement or full replacement
• Attic access, height and working conditions
• Design changes, such as added returns or resized trunks
• Replacing plenums, boots and registers
• Mold protocol requirements, if any

Most of those only show up in the attic, so a quote starts with a look at your ducts: call 512-489-4653 or schedule online. Homeowners may qualify for utility rebates on duct sealing through whole-home efficiency programs; see our rebates page and check current terms.

Curious why the room at the end of a long flex run stays warm, or what Manual D actually sizes? Start here:

• Smart HVAC Design: Manual J, D and S Explained
• Understanding Your Home’s Duct System
• Why Properly Sized Ductwork Matters
• Duct System Optimization: Boosting Efficiency and Comfort
• Where Your Home Actually Leaks: A Central Texas Guide to Air Infiltration

See every ductwork and home comfort guide in the Resource Center