Ductwork Repair and Airflow Fixes in Kennesaw, GA

Ducts are out of sight, so the clues show up in the rooms:

• Rooms that never reach the thermostat setting, usually upstairs or at the far end of the house
• Strong airflow at some registers and barely a breath at others
• A system that runs nonstop on hot afternoons and still falls behind
• Dust that returns a day after cleaning, or dark streaks around registers
• A musty smell at startup, especially from a crawl space system
• Sweating registers or ceiling stains near supply vents in summer

A weak capacitor or low refrigerant charge can also leave rooms warm, so the technician checks the equipment before blaming the ducts. If cooling is weak in every room, start with AC repair or the safe checks for an AC that is not cooling.

Kennesaw subdivisions are full of two-story homes from the late 1990s and 2000s, and most have a warmer second floor. Part of that is physics. Much of it is duct design.

Why the second floor runs hot

• The attic bakes the rooms below it. On a July afternoon the attic runs far hotter than the yard.
• Long supply runs through that attic. Leaky or thinly insulated duct warms the air before it reaches the bedroom.
• Too few returns. With bedroom doors closed and one central return in the hall, rooms pressurize and supply air struggles to get in.
• One thermostat for two floors. The downstairs thermostat is satisfied long before the bedrooms are.

What usually helps

Sealing and insulating attic ducts, adding a return or transfer grille to closed-off bedrooms, resetting balancing dampers, and in some homes zoning or a separate upstairs system. Our guide on why the upstairs is so hot in a two-story home explains each option. It is also the complaint we hear most from Towne Lake and other Woodstock neighborhoods.

Most homes built here since the 1990s use flex duct: a plastic liner wrapped in insulation and a foil or plastic jacket. It works well when run straight, supported and sealed. Twenty years in a Georgia attic is hard on it.

• Sagging. Unsupported spans droop into bellies that choke airflow.
• Crushing and kinks. Storage boxes, insulation crews or tight bends at a boot can cut a room's air to a trickle.
• Disconnections. Straps loosen, liners slip off their collars, and a bedroom supply ends up cooling the attic.
• Torn jackets. Humid attic air reaches the cold liner, the duct sweats, and the insulation soaks through.
• Leaky returns. A gap on the return side pulls hot, dusty attic air into the system, past the filter.

Crawl space ducts

Crawl space ducts share these problems plus ground moisture, and a disconnected run under the floor draws musty air into the house. Older homes near the Marietta historic districts often have mixed metal and flex systems added in pieces over the decades.

Sealing

Joints and collars are sealed with duct mastic or approved foil tape, not cloth duct tape, which lets go in attic heat. The joints at the air handler and plenums matter most. A duct leakage test pressurizes the system and measures escaping air, before and after.

Insulation

Attic supply ducts need full insulation so cooled air arrives cool and the duct does not sweat. Many older homes have thinner duct insulation than current energy codes call for.

Replacement

When flex duct is brittle, flattened or soaked, sealing it is wasted effort. New runs let the contractor correct sizes, add returns and route ducts straight, following ACCA Manual D. If you are planning AC installation or replacement, have the ducts evaluated at the same visit; a new system on leaky ducts will not deliver its rated efficiency.

Tight ducts can still send air to the wrong rooms. Balancing and zoning fix the distribution.

Balancing dampers

Many branch ducts near the air handler have a small lever: a balancing damper. The technician measures airflow at the registers and sets the dampers so each room gets its share. Some two-story homes shift them toward the upstairs in summer and downstairs in winter. Closing supply registers is not the same thing; it raises duct pressure and pushes more air out of the leaks.

Zoning

Zoning uses motorized dampers, a thermostat for each floor and a control panel, so one system serves two floors more evenly. It must be designed around the equipment, because a single-speed system can push too much air into one small zone. Two-stage or variable-speed equipment is a better match.

Two systems, still hot upstairs

If you already have separate units and the upstairs still lags, the cause may be missing returns, attic duct losses or an undersized upstairs system. Measurements show which.

In Kennesaw the two biggest air quality factors are spring pollen and summer humidity.

Filtration

A cabinet holding a 4 or 5-inch media filter catches more pollen with less restriction than a dense 1-inch filter. Sealing return ducts matters just as much, since a leaky return lets attic dust skip the filter. Our HVAC maintenance page covers filter sizes and change schedules.

UV lights

UV lamps near the indoor coil help limit mold growth on the coil and drain pan, which stay wet all summer. They do not clean ducts or stop leaks, and the lamps need periodic replacement.

Whole-home dehumidifiers

Your AC removes moisture only while it runs. In muggy spring and fall weather, or with an oversized system that short-cycles, humidity stays high. A ducted dehumidifier dries the house without overcooling it, which helps most in homes with basements or crawl spaces.

Duct work starts with finding out where the air goes, because guessing leads to sealing the easy joints and missing the big leak behind the air handler. A duct visit covers:

• Room-by-room airflow. Supply temperatures and airflow at the registers, upstairs and down, compared with what each room needs.
• Static pressure. A pressure reading across the system that shows whether ducts and filters are choking the blower.
• Attic and crawl space inspection. Every reachable run checked for kinks, sags, crushed sections, torn jackets, disconnected boots and loose plenum joints.
• Return air check. Whether the upstairs has enough return capacity, a common gap in two-story homes built in the 1990s and 2000s.
• Sealing with the right materials. Joints sealed with mastic or UL 181 rated foil tape, not cloth duct tape that dries out and falls off in attic heat.
• Insulation repair. Torn or missing jacket replaced so cold ducts stop sweating in humid summers.

When numbers matter, such as before and after a sealing job, a duct leakage test measures the leak rate with a calibrated fan and pressure gauge. ENERGY STAR estimates that a typical home loses 20 to 30 percent of the air moving through its ducts to leaks and poor connections.

1. Call (321) 478-0693. Describe the symptom: hot rooms, weak vents, dusty air, sweating ducts or a high bill, and which floor it affects.
2. Measure first. The technician takes temperatures and pressures with the system running, so the fix targets the real restriction or leak.
3. Inspect the runs. Attic and crawl space ducts are traced from the air handler to each problem room.
4. Options and price. You get the findings and a written price for each option, from sealing and strapping a few runs to adding a return or replacing a section of duct.
5. Repair. Runs are reconnected, straightened and supported, joints are sealed with mastic or UL 181 tape, and damaged insulation is replaced.
6. Re-measure. Airflow and temperatures are checked again so you can see the change, not just hear about it.

The price is quoted after the technician has seen your system. The main factors:

• Access: a decked attic is quicker work than a low attic, a tight crawl space or ducts in finished ceilings
• Scope: resealing a few joints versus replacing every run
• Materials: flex or rigid duct, insulation, mastic, new boots or plenums
• Testing and design: leakage tests and airflow readings show what actually needs fixing
• Add-ons: zoning, a new return, a media filter cabinet, UV lamps or a dehumidifier
• Equipment age: an aging system may make pairing duct work with a replacement the smarter move

You hear the price before work starts. Every HVAC contractor we send is licensed and insured in Georgia.

We cover Kennesaw, Acworth, Woodstock, Marietta and the rest of our service area. Call (321) 478-0693 to have your ducts checked.