Lennox Ductwork Repair Nationwide | Dalton Heating & Air Miami

Lennox Ductwork Repair: The Miami Owner’s Guide

Lennox ductwork repair in Miami typically runs $175 – $765 installed, depending on whether we’re sealing a failed joint, replacing a crushed trunk section, or rebuilding a plenum connection at the air handler. Most jobs are completed same day, and we carry Lennox-compatible duct fittings, mastic, and reinforced flex on the truck. The way most Miami homeowners discover they need this is subtle at first: one room stops cooling while the rest of the house feels fine, or the utility bill climbs $40 – $60 a month with no change in thermostat settings. That’s air, paid for and conditioned, leaking into the attic instead of reaching the rooms you actually live in.

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Which Lennox Models This Applies To

This applies to virtually every Lennox split system and packaged unit installed in Miami over the past twenty years, from the Merit series (ML14, ML17) up through the Elite and Signature lines. The ductwork itself is not model-specific in the way a control board is. What matters is the connection point at the air handler and the design of the supply and return plenums, which are sized to the unit’s CFM output. A Lennox ML180 furnace pushing 1,200 CFM needs a different plenum transition than a lower-airflow Signature unit. The compatibility gotcha we see in Coral Gables and older Miami neighborhoods is this: homes built before 2005 often have undersized returns, sometimes a single 14-inch return feeding a 2.5-ton Lennox system. That return was marginal when it was installed, and once the ductwork ages and flex liner sags, the system starves for air. For OEM versus aftermarket: Lennox-branded rigid duct fittings and plenums are quality but priced at a premium. For most repairs, we use galvanized material and commercial-grade flex that meet or exceed the original spec, and we stand behind the work the same way. Dalton Heating & Air Miami is an independent service provider, not affiliated with Lennox, but our technicians are factory-trained on Lennox equipment and diagnose the ductwork as part of the whole system, not in isolation.

Signs Your Lennox Ductwork Repair Is Failing

• One or two rooms never reach set temperature. This is usually a disconnected duct or a crushed flex run in the attic. In Miami’s humidity, the attic is a hostile place, and old duct tape fails, leaving the duct hanging or resting on ceiling joists.
• Dust builds up fast after cleaning. Return-side leaks pull unfiltered attic air, insulation fibers, and dust directly into your Lennox system. You’ll notice it most on the grill in the hallway return.
• Utility bill climbs with no change in usage. Leaking supply ducts bleed conditioned air into the attic, and your Lennox unit runs longer to satisfy the thermostat. We regularly see a 15 – 25 percent loss in cooling capacity from duct leaks alone in Miami homes.
• Whistling or fluttering noise from a vent. A whistling register usually means a duct has come partially loose, and air is escaping through a narrow gap under pressure. Fluttering is often a loose damper or separated inner liner inside the flex duct.
• Condensation or water stains on the ceiling. When a duct sweats continuously in Miami’s damp attic air, the moisture eventually shows up on drywall. This is both a duct sealing issue and a sign that attic ventilation may need attention.

Replacement Cost & What’s Included

In Miami, most Lennox ductwork repairs land between $175 and $765. At the low end, that’s resealing a leaking joint, reconnecting a separated flex run, or replacing a short section of damaged trunk line. At the higher end, you’re looking at rebuilding a plenum, replacing a long portion of collapsed return duct, or reworking duct sizing at the air handler. The price is written before any work starts, and it includes the parts, the labor, and the cleanup. Every repair is guaranteed in writing for a full year through the 365-Day Done Right Promise. If the repair fails in that time, we return at no charge. That’s the standard, and it applies whether the job is $175 or $765. We don’t charge overtime for emergency calls, and there’s no service fee added when the work goes ahead.

DIY or Call Us?

You can safely check a few things yourself: look for visible gaps at the air handler connection, listen for whistling at registers, and check whether any vents in unused rooms are fully closed, which drives up static pressure in a Lennox system. What you should not do is climb into a Miami attic in August to tape a duct joint. The temperature up there routinely exceeds 130 degrees, and one wrong step through the ceiling is a $1,500 drywall repair on top of the ductwork. If the duct is leaking at the plenum or the return is undersized, that’s not a tape job, that’s a system correction. Call us at (850) 754-6042, and we’ll show up with a written price before touching anything. Tell me what it’s doing, I’ll tell you what it costs, in writing, before I touch it.

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