Keep the comfort
inside the ducts.

Sealing, insulating and cleaning do different jobs

EPA does not recommend routine duct cleaning for every home. A dusty grille alone is not proof that the entire duct system needs cleaning. Start with the problem you are trying to solve.

Why a small gap can matter

Want to explore the difference? Our heating-loss scenario calculator compares insulation, sealing and both using visible, editable assumptions. It is an illustration, not a measurement or savings guarantee.

A supply leak can send heated or cooled air into an attic instead of a room. A return leak can draw unwanted air from the surrounding space into the system. Leaks can also affect pressure relationships and bring in dust or other contaminants. ENERGY STAR explains the comfort, air-quality and combustion-safety connections.

ENERGY STAR estimates that a typical home can lose 20–30% of the air moving through its ducts through leaks and poor connections. That is not a measured result for your house, and it does not mean sealing will cut your utility bill by 20–30%. Duct location, leakage and system operation all matter.

Why sealed ducts may still need insulation

An airtight metal duct can still exchange heat with a cold basement or hot attic. DOE recommends sealing and insulating ducts in unconditioned spaces: one controls air leakage; the other limits heat transfer. Whether a basement is actually inside the conditioned enclosure needs checking—not guessing from its name.

Insulation needs continuous coverage and correct contact with the duct. Its R-value, thickness and installation method should suit the system and applicable requirements. Crushing insulation or leaving gaps weakens the result. A shiny outer jacket by itself is not proof of adequate insulation.

What about sweating ducts?

Cold duct surfaces can collect condensation when surrounding air is humid. A suitable insulation system and intact vapor-resistant jacket help control that risk. Do not wrap over wet or damaged insulation: first identify the moisture source and assess what needs replacement. EPA emphasizes correcting moisture problems, not hiding them.

What you can check without opening anything

• Note rooms that stay unusually hot or cold and whether the problem changes with the season.
• From a safe standing position, photograph visible separated joints, crushed flexible ducts, torn jackets or water staining. Do not move ducts or peel insulation back.
• Keep supply and return grilles clear of furniture. Check a routinely accessible filter according to the filter-care guide.
• Record when noise, weak airflow or condensation appears. These observations help narrow the inspection; they are not a diagnosis.

A useful repair includes measurements

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Ask for an inspection of both supply and return paths, including damaged connections and restrictions. A technician can assess leakage, total external static pressure and delivered airflow as appropriate, then verify operation after repairs. Sealing does not fix undersized returns or a crushed duct. ENERGY STAR’s contractor checklist includes airflow evaluation and combustion-safety testing.

Connections need suitable duct mastic or tape approved for the duct type and application, following the manufacturer’s instructions. DOE identifies appropriate UL 181-family sealing products. Ordinary cloth-backed “duct tape” is not a durable substitute. The proposal should separate repairs, sealing, insulation and access work.

For replacement planning, review the ducts alongside the home’s load and the proposed equipment’s airflow. Do not choose a larger unit simply to compensate for a cold room. Read how home insulation and air sealing affect HVAC demand and our heat pump, gas and oil comparison.

Common questions

Should every duct be insulated?

Location and existing construction matter. Prioritize an assessment of ducts outside the conditioned enclosure; already insulated ducts may need repairs rather than another layer.

Will sealing fix every uncomfortable room?

No. Equipment faults, duct sizing, filter resistance, room heat loss and return-air paths can produce similar symptoms. Identify the cause before choosing the work.

Is duct repair included in a tune-up?

Do not assume so. Inspection, repair, sealing and insulation are different scopes. Check the service price guide; HVAC PM confirms the proposed work and price before it begins.