Ductwork Installation in Seattle, WA

Ductwork projects in Seattle typically range from $3,450 to $9,200, depending on scope. A partial replacement of a few crushed or leaking runs is at the lower end. A complete custom-fabricated duct system for a 2,000-3,000 sq ft home with all-new trunk lines, mastic sealing, and R-8 insulation is at the higher end. We provide free in-home assessments with written, itemized estimates.

Yes. The mechanical permit is issued by Seattle Department of Construction & Inspections (SDCI), and Washington State requires one for this work. We handle the whole thing — application, fee, and meeting the inspector for the final — so you never contact the permit desk yourself. In Seattle, exterior equipment may additionally need sign-off from the Seattle Landmarks Preservation Board and the neighborhood historic districts (Ballard Avenue, Columbia City, Pioneer Square, Harvard-Belmont), which we factor into placement before we quote. Every install meets or exceeds the current Washington State mechanical and energy codes.

Most ductwork projects in Seattle take 1-3 days. A targeted replacement of a few problem runs is often a one-day job. A complete duct system replacement paired with a new furnace or heat pump install runs 2-3 days, including commissioning and balancing. We schedule to minimize disruption and always leave your home clean.

Almost always, the cause is ductwork: undersized supply, missing or unbalanced damper, kinked flex duct, leaky takeoff, or no return air path. We diagnose the actual cause with manometer readings and airflow measurements — not guesses — and propose the smallest fix that actually solves the problem.

We fabricate our own galvanized sheet metal trunk lines, plenums, and transition fittings. We use rigid metal supply runs wherever possible and limit flex duct to short, properly supported connections at registers. All joints are sealed with mastic (not tape). All ducts in unconditioned space (attics, crawl spaces) are insulated to R-8 minimum. No subcontractors and no shortcut materials.

Often, yes — at minimum, you should have it inspected. A new high-efficiency furnace or variable-speed heat pump can lose 20-30% of its rated performance through leaky, undersized, or improperly sealed ductwork. If your existing ducts are 25+ years old, leaking visibly, or were sized for a smaller previous unit, it's almost always worth replacing or modifying them as part of the equipment install.

The Washington State Energy Code lists Seattle at a 24°F winter design temperature (WAC 51-11C-80100, Table C-1). That is the number a Manual J load calculation for your home is run against, and it is the difference between duct runs sized for the real load and duct runs sized for a guess. A cold-climate heat pump holds its rated capacity well below that, which is why heat pumps genuinely work here rather than being a compromise. Gas here comes from Puget Sound Energy, and for some homes a hybrid — heat pump for most of the year, gas furnace for the coldest mornings — is the right answer. We will tell you if it is.