Ductwork distributes conditioned air. Leaks, poor layouts, and undersized returns waste energy and leave rooms uncomfortable, even when the equipment works well.
Draft. Some reference links and cost figures are still being verified.
Ductwork distributes conditioned air through the home. Leaks, poor layouts, and undersized returns waste energy and leave rooms uneven, even when the equipment works well.
| Question | Short answer |
|---|---|
| How much energy do leaky ducts waste? | A Lawrence Berkeley National Laboratory deck hosted on energy.gov estimates about 30 percent leakage on each side of the fan for basement ducts and about 15 percent for attic or crawlspace ducts. |
| What does sealing save? | The same deck estimates heating and cooling savings of about 10 percent from sealing basement ducts and 15 to 20 percent for attic or crawlspace ducts. |
| What does it cost? | 2026 guides put installed flexible duct at about $10 to $30 per linear foot, and sheet metal or replacement with removal at about $25 to $60 per linear foot. Whole-home work often runs into the thousands. |
| When do I need a pro? | Duct design, replacement, leak testing, and sealing with mastic or aerosol methods. |
Supply ducts carry conditioned air from the air handler to rooms through registers. Return ducts bring air back to the air handler. Balanced airflow depends on duct size, sealing, and return paths. Filters and grilles also affect how much air moves.
| Problem | Likely cause | Fix |
|---|---|---|
| Hot and cold rooms | Unbalanced airflow, undersized or missing returns, or leaks | Test airflow, seal leaks, and add returns where needed |
| Dust around registers | Leaks drawing in attic or crawlspace air, or unsealed joints | Seal the joints and check the filter |
| Whistling at registers | Restricted airflow or a loose grille | Clear the register and check the filter |
| High energy bills | Leaks in unconditioned spaces | Seal and insulate ducts in attics, crawlspaces, and garages |
| Ducts damaged or disconnected | Age, pests, or foot traffic | Repair or replace damaged sections |
| Symptom | Possible meaning | Next step |
|---|---|---|
| Strong dust or mold smell from vents | Contamination or moisture in ducts | Call an HVAC technician for inspection |
| Visible disconnected or crushed duct | Lost airflow and energy loss | Repair or reconnect the section |
| Duct board or flex duct soaked or moldy | Water intrusion | Replace the damaged section; find the water source |
| Task | Homeowner? | Notes |
|---|---|---|
| Replace the filter and clean grilles | Yes | Check the filter monthly and replace at least every three months (ENERGY STAR) |
| Open or close registers to rebalance | Yes | Avoid closing many registers, which can strain the system |
| Seal joints with mastic or approved tape | Limited | Use mastic or foil-backed approved tape, not cloth duct tape |
| Duct design, load calculation, or leak testing | No | Licensed HVAC contractor |
| Job | Typical range | Notes |
|---|---|---|
| Flexible duct, installed | About $10 to $30 per linear foot | Materials and labor; varies by region |
| Sheet metal or replacement with removal | About $25 to $60 per linear foot | Tear-out and disposal add cost |
| Whole-home replacement | Often in the thousands of dollars | Depends on home size and layout |
These are estimates from published 2026 guides. Get a written quote that includes a duct design or a load calculation.
| Condition | What changes | Advice |
|---|---|---|
| Hot climates with attic ducts | Hot attics raise duct losses | Seal and insulate attic ducts |
| Cold climates with unconditioned crawlspaces | Cold air and moisture can condense in ducts | Insulate and seal ducts in unconditioned spaces |
| Humid climates | Moisture management relies on return airflow | Confirm return sizing and drainage |
No. Cloth-backed duct tape does not last. Use mastic or approved foil tape, or ask a professional to seal the ducts.
Sealing helps any system, but an old system may still need replacement. Ask a technician to test the whole system first.
| Term | Meaning |
|---|---|
| Supply duct | The duct that carries conditioned air to a room |
| Return duct | The duct that brings room air back to the air handler |
| Mastic | A sealant applied to duct joints |
| Static pressure | The air pressure inside the duct system; a test of airflow restriction |
Sources reviewed November 4, 2026. Independent professional review: pending. Confirm local rules with your building department.
| Service | When you need it | Typical cost (2026 guides) | DIY or pro | Permit usually? |
|---|---|---|---|---|
| Duct leak sealing (mastic or aerosol) | Leaks, hot or cold rooms, or high bills | Manual mastic about $300 to $1,900; aerosol (Aeroseal) about $800 to $3,800 (HomeGuide, PickHVAC, Angi; estimates vary) | Licensed HVAC contractor for whole-house work | Usually not |
| Duct section repair or replacement | Damaged, crushed, or disconnected duct | Varies; about $25 to $60 per linear foot for replacement with removal | Licensed HVAC contractor | Sometimes |
| Register or grille repair | Damaged or loose grille | Low cost; homeowner task | Homeowner | No |
| Service | When you need it | Typical cost (2026 guides) | DIY or pro | Permit usually? |
|---|---|---|---|---|
| Duct cleaning | Visible dust, after renovation, or mold concern | About $300 to $700 for a typical home (Fixr, CostInsight); $375 to $500 average range | Licensed duct cleaning company | No |
| Filter replacement | Check monthly; replace at least every three months (ENERGY STAR) | Parts cost only; homeowner task | Homeowner | No |
| Return air check | Yearly, or when rooms are uneven | Included in many HVAC tune-ups | Licensed HVAC technician | No |
| Service | When you need it | Typical cost (2026 guides) | DIY or pro | Permit usually? |
|---|---|---|---|---|
| Ductwork replacement | Old, undersized, or damaged ducts | About $10 to $30 per linear foot for flex; $25 to $60 for sheet metal (2026 guides) | Licensed HVAC contractor | Usually yes |
| Duct design or load calculation | New equipment or added rooms | Get a quote; usually bundled with equipment | Licensed HVAC contractor | Usually yes |