Ductwork Install & Replace
When ducts are too damaged or undersized, replacement may be better than sealing.
Duct sealing for Affton, MO homes
Duct Sealing that keeps the air you pay for inside your home
Leaky ducts quietly waste heated and cooled air in attics, crawlspaces and wall cavities. We find the leaks, seal them with durable materials, and show you the difference in measured results.
- Leak location and testing
- Mastic and approved tapes
- Before and after comparison
Why duct sealing matters
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. That lost air has already been heated or cooled, so the equipment has to run longer to make up for it.
Leaks on the return side can be just as problematic. They pull air from attics, crawlspaces or garages into the system, bringing dust, insulation fibers and humidity with it. In homes with combustion appliances, significant duct leakage can also affect pressure balance.
Duct sealing addresses these losses directly, improving comfort, reducing runtime and helping the system deliver the air it was designed to.
Rooms hard to heat or cool and energy bills climbing? Call to schedule a duct leakage evaluation.
Click Here To Call (888) 418-3681Our duct sealing approach
Effective sealing depends on finding the leaks and using materials that last.
Locating leaks
We inspect accessible ductwork in attics, basements and crawlspaces, paying close attention to connections at the air handler, plenums, takeoffs, elbows and boots where ducts meet registers. Where appropriate, a duct leakage test using a calibrated fan pressurizes the system to quantify how much air is escaping.
Sealing materials
Water-based duct mastic is brushed onto joints and seams, often with fiberglass mesh for larger gaps. Where tape is appropriate, we use foil tapes listed for duct sealing. Ordinary cloth duct tape is avoided because its adhesive dries out and fails. Large holes and disconnected sections are repaired mechanically before sealing.
The air handler and plenums
Some of the largest leaks occur right at the equipment, where the supply and return plenums connect to the air handler or furnace. Unsealed filter slots and panel gaps also leak. These areas are sealed carefully while keeping service access available.
Registers and boots
The connection between the duct boot and the ceiling, wall or floor is a common leakage point, especially in ceilings below attics. We seal these gaps from inside the room or from the attic side, depending on access, to stop conditioned air escaping and attic air entering.
What duct sealing can and cannot change
Sealing is one of the more cost-effective improvements for many homes, but results depend on where the leaks are and where the ducts run. A realistic picture before the work begins leads to realistic expectations afterward.
Where leakage matters most
Leaks in ducts that run through the attic, crawlspace or garage matter most, because conditioned air escapes to places you are not trying to heat or cool. Supply leaks send paid-for air outdoors in effect, and return leaks pull in dusty, hot or cold air from those spaces. Leaks in ducts that run entirely inside the living space still affect how evenly rooms are served, but the energy lost stays within the home, so the payoff tends to be smaller.
Measuring before and after
A duct leakage test uses a calibrated fan to pressurize the duct system with the registers temporarily covered, then measures how much air escapes at a set test pressure. Recording that figure before sealing and again afterward turns the result into a number rather than an impression. Where access or the scope of work makes a full test impractical, we explain what was inspected visually and what was not.
Why tape alone is not enough
Standard cloth-backed duct tape tends to dry out and release over time, especially in hot attics. Lasting seals rely on mastic, a thick paste applied over joints and seams, sometimes reinforced with fiberglass mesh on larger gaps, and on foil tapes listed for duct sealing where tape is appropriate. Before any sealant goes on, the connection must be mechanically secure, since sealant is not meant to hold a loose joint together.
Combustion safety and return leaks
In homes with a furnace or water heater that draws combustion air from the room, return duct leaks near those appliances can lower the air pressure in the space and interfere with how exhaust gases vent. Sealing return leaks in a furnace closet or basement mechanical room therefore has a safety benefit as well as an efficiency benefit. We also check that combustion appliances still draft properly once the work is complete.
The ducts we cannot reach
Duct runs sealed inside finished walls, floor cavities or ceilings are often inaccessible without opening surfaces. In those areas, we seal what can be reached at the boots, registers and trunk connections, and we tell you plainly which sections remain unsealed. If hidden leakage appears to be significant, we discuss options, including whether internal sealing methods or a partial duct replacement would be worth considering.
Checking the blower afterward
Sealing leaks changes how air moves through the system. More of it reaches the rooms, and in some systems the static pressure rises slightly because air is no longer escaping through gaps. We check blower operation and static pressure after sealing, and where rooms now receive more air than needed, we adjust the balancing dampers so the gain is spread evenly.
Pairing sealing with insulation
Sealed ducts in an attic still lose heat through their walls if the insulation is thin, torn or missing. Where we find damaged insulation during sealing, we note it and can quote repairs. Addressing both at once is usually more efficient than returning to the attic twice.
How to spot likely leaks yourself
You can look for a few clues before a technician arrives. Dirty streaks around ceiling registers can point to air being pulled from the attic around the boot. Dust lines on insulation near duct joints, disconnected sections visible in a crawlspace, or a whistling sound from the return side all suggest leakage. Rooms that are dustier than others, or a furnace closet that feels drafty when the system runs, are worth mentioning as well. Avoid crawling across attic joists or disturbing old duct wrap to investigate, and leave the detailed inspection to us.
Expected results and timeline
Many homes can be sealed in a single day when ducts are reasonably accessible, while complex attics or crawlspaces may need longer. Afterward, households often notice rooms reaching temperature more evenly, less dust on surfaces and quieter operation. Energy savings depend on how much air was leaking and where, which is why measured before and after results are so useful. We share those figures with you so you can judge the improvement yourself rather than relying on estimates, and we note any unsealed sections that could be addressed later.
Signs your ducts may be leaking
Duct leakage shows up in several ways.
High energy bills
Leaks force the system to run longer to maintain temperature.
Rooms that never feel right
Rooms at the end of long runs often receive less air than intended.
Dust buildup
Return leaks pull dust and debris into the airstream.
Stuffy or humid rooms
Leaks can reduce airflow and draw humid air from unconditioned spaces.
Visible gaps or loose tape
Peeling cloth tape and separated joints are clear signs of leakage.
Ducts in attics or crawlspaces
Ducts in unconditioned areas lose the most energy when they leak.
How duct sealing is carried out
Our duct sealing visits follow these steps.
Inspection
Accessible ducts are examined and leak points are documented.
Testing
Where appropriate, a duct leakage test measures total leakage before work begins.
Repairs
Disconnected or damaged sections are reattached or replaced.
Sealing
Joints, seams, plenums and boots are sealed with mastic or listed foil tape.
Retesting
Leakage or airflow is measured again so you can see the improvement.
What affects duct sealing cost
Your quote reflects the conditions found during the assessment.
| System size | Larger duct systems have more joints and seams to seal. |
|---|---|
| Accessibility | Ducts in tight attics or behind finished surfaces take longer to reach. |
| Repairs needed | Disconnected or damaged sections add materials and labor. |
| Testing | Duct leakage testing before and after adds measurable verification. |
| Insulation | Removing and replacing duct insulation to reach seams increases scope. |
Homeowners on duct sealing
What changed after the work.
The return plenum had a gap you could fit your hand through. After sealing, the upstairs rooms cool noticeably faster.
I liked seeing the leakage test numbers before and after. It made the value of the work obvious.
Less dust on the furniture since the returns in the crawlspace were sealed.
Duct sealing questions
What Affton, MO homeowners want to know.
Is duct tape good for sealing ducts?
Ordinary cloth duct tape is not recommended because its adhesive fails over time. Mastic and listed foil tapes are preferred.
Can all ducts be sealed?
Accessible ducts can be sealed directly. Ducts hidden in walls or ceilings may be sealed at connections or evaluated for other methods.
Will duct sealing improve comfort?
Yes, in most homes with leaky ducts. More air reaches rooms, and less unconditioned air is drawn in.
Does duct sealing help with dust?
Sealing return leaks reduces the dust and debris pulled into the system from attics and crawlspaces.
How long does duct sealing take?
Many homes can be completed in a day, depending on the size and accessibility of the system.
Stop paying for air you never feel
Call to schedule duct sealing in Affton, MO and see measured improvements.
Duct sealing includes
- Leak inspection
- Repair of disconnected sections
- Mastic and listed tape sealing
- Before and after measurement