Ductwork carries every heated or cooled BTU your equipment produces. If ducts leak, are undersized, or run through unconditioned attics and crawlspaces, you pay for conditioning air that never reaches your rooms. Common symptoms include uneven temperatures, dusty registers, high utility bills, and rooms that never feel comfortable despite new equipment.
Not every project needs all-new ducts. Professional testing—often with a duct leakage test or blower door assessment—can quantify how much air is lost. Sealing accessible leaks with mastic or approved tape, adding insulation where ducts pass through hot attics, and correcting crushed flex runs may solve problems at lower cost than full replacement. If leakage is moderate and ducts are accessible, repair is frequently the right first step.
Replacement is more justified when ducts are collapsed, riddled with inaccessible leaks, sized incorrectly for the new equipment, or contaminated beyond cleaning. A major equipment upgrade paired with old, leaky ducts often fails to deliver the comfort and efficiency the new unit is capable of. In that case, duct renovation belongs in the scope—but it should be supported by testing or clear documentation, not a blanket recommendation on every bid.
Ask contractors how ducts were evaluated, what leakage target they design to, and whether return air paths are adequate. High static pressure from poor duct design can reduce airflow and shorten equipment life. Independent review helps separate necessary duct work from generic “replace it all” language that inflates price without fixing the real bottleneck.