Air Duct Sealing Services

Reviewed 2026-07-30

Air duct sealing closes leaks, gaps, and disconnected joints in supply and return ductwork. Sealed ducts stop wasted heated and cooled air, even out room temperatures, and keep dust out of the system.

Symptoms air duct sealing solves

Some rooms are noticeably hotter or colder than others
Energy bills are high relative to the size of the house
Visible dust buildup around vents or a persistently dusty house
Ducts run through an unconditioned attic, crawl space, or garage
You can hear air whistling or feel drafts near duct joints or boots
The HVAC system runs long cycles without evenly conditioning the house
A home energy audit flagged high duct leakage

When to book air duct sealing

After a home energy audit identifies duct leakage above 15-20% (ENERGY STAR flags 20-30% as typical for unsealed systems)
Before finishing an attic or basement where ducts are exposed and accessible
When rooms far from the air handler are chronically uncomfortable
As part of any HVAC replacement, since sealing ducts optimizes the new equipment's performance

What happens during air duct sealing

Technician performs a duct leakage test (often a duct blaster) to quantify total leakage as a percentage of system airflow
Accessible ducts are visually inspected for disconnected sections, crushed runs, and gaps at boots and plenums
Leaks are sealed with mastic sealant or metal-backed tape (not standard cloth duct tape, which fails within a few years)
Insulation is added or repaired on ducts running through unconditioned spaces
A post-sealing duct blaster test verifies leakage reduction
Technician provides before/after leakage percentages and airflow readings at registers

Air Duct Sealing methods and approaches

Manual mastic sealing

Technicians apply duct mastic by hand to every visible seam, joint, and connection point — the most durable and widely recommended method, especially for accessible attic and basement ducts.

Aeroseal (aerosolized duct sealing)

A sealant is injected into the duct system under pressure, plugging leaks up to 5/8 inch from the inside, including runs hidden inside walls and floors that can't be manually reached.

Insulation and mechanical repair

Reconnecting disconnected duct sections, replacing crushed flex duct runs, and adding R-6 to R-8 insulation wrap on ducts in unconditioned spaces per ENERGY STAR recommendations.

What drives air duct sealing pricing

Total linear footage and accessibility of ductwork
Manual sealing versus Aeroseal (Aeroseal typically costs more but reaches hidden leaks)
Whether duct insulation replacement is included
Number of separate duct systems/zones in the house
Pre- and post-sealing diagnostic testing fees
Extent of damage requiring duct replacement rather than sealing alone

See the full cost guide →

Compare your options →

Questions to ask your hvac technician or duct specialist

Will you test leakage before and after with a duct blaster, and share both numbers?
Do you use mastic sealant or Aeroseal, and why for my situation?
What percentage of leakage reduction should I expect?
Are there any duct sections that need replacement rather than sealing?
Will sealing address my uneven room temperatures, or is more airflow balancing needed?
Is duct insulation included, or priced separately?

Air Duct Sealing safety and licensing

Don't use standard cloth-backed duct tape for sealing — it degrades and fails within a few years despite its name; only mastic or foil (UL 181) rated tape holds long term.
If ducts run through a crawl space or attic, watch footing and insulation contact carefully — technicians should protect wiring and avoid disturbing vermiculite insulation, which may contain asbestos in homes built before 1990.
Ensure combustion air supply to gas furnaces isn't restricted when sealing return ducts, per NFPA 54 guidance on appliance venting.

Air Duct Sealing questions homeowners ask

How much air leakage is normal in ductwork?

ENERGY STAR reports typical unsealed residential duct systems lose 20-30% of moved air to leakage; a well-sealed system should be under 10%.

Does duct sealing lower energy bills?

Yes — sealing ducts in unconditioned spaces like attics reduces the amount of conditioned air lost before it reaches living spaces, which is one of the most cost-effective efficiency upgrades available.

Is duct sealing the same as duct cleaning?

No. Cleaning removes dust and debris from inside ducts; sealing closes physical leaks in the duct system. They solve different problems and are often sold together but aren't interchangeable.

Problems that lead to air duct sealing

Sources for this air duct sealing guide

ENERGY STAR duct sealing and home performance guidance
U.S. Department of Energy duct efficiency resources
ASHRAE residential ventilation and duct design standards