How much does ductwork replacement cost in Kent, WA?

Figure $3,000 to $8,000 installed for a typical Kent home. Kent, Auburn and Federal Way all price in Varsity's standard market tier, so a single-level rambler with an open crawlspace lands near the bottom of that range and a two-story home with attic runs, a tight crawl and a new return trunk lands near the top. Targeted repairs or modifications cost less than a full replacement.

Do I need all new ducts when I install a heat pump?

Usually not. Most 1960s-1990s South King County homes have sheet metal trunk lines that are still structurally sound, and the fix is sealing joints, replacing failed flex branches, and correcting undersized returns. A heat pump moves more air at a lower temperature than a furnace, so return capacity gets checked carefully, but full replacement is the exception rather than the rule.

How long does a ductwork job take?

A full replacement typically takes two to four days. Simple modifications, added runs, or a return upgrade usually take one to two days and are often bundled into a heat pump or furnace installation so there is one crew, one permit and one inspection.

Is a permit required for duct replacement in Washington?

Yes, mechanical work including duct replacement generally requires a permit, and Kent, Auburn and Federal Way each issue their own. Varsity pulls the permit and schedules the inspection as part of the job, no exceptions.

Ductwork Cost in Kent, Auburn & Federal Way Homes (2026)

Q: Do utility rebates cover ductwork?

Local utility rebates are generally tied to qualifying heat pump equipment, not duct-only work, and the amount depends on what is being replaced and the equipment installed. Programs change and pay only through their own contractor networks, so Varsity confirms what your utility actually pays before quoting and files the paperwork.

Three cities, one housing story. Kent, Auburn and Federal Way were largely built out between the 1960s and the 1990s — ramblers, split-levels, and two-story tract homes sitting over vented crawlspaces. The furnaces in those homes have been replaced once or twice. The ducts, in a lot of cases, have never been touched.

That is why we get so many calls that start as "my heat pump isn't keeping up" and end as a duct conversation. Here is what ductwork actually costs in these three cities in 2026, what drives the number up, and how to tell whether you have a duct problem or an equipment problem before you spend anything.

What ductwork costs in Kent, Auburn and Federal Way

All three cities price in the standard market tier. No affluent-market premium, no luxury premium. That means:

Scope	Installed cost
ScopeFull duct replacement, typical home	Installed cost$3,000 – $8,000
ScopeDuct modification or partial replacement	Installed costLess than a full replacement, scoped per job
ScopeDuct work bundled with a new system install	Installed costPriced as one combined scope

Where you land inside that range comes down to four things:

Access. An open, tall crawlspace with a vapor barrier is cheap to work in. A 24-inch crawl with standing-water history, old insulation hanging down, and a maze of plumbing is slow, and slow is expensive.
How much is actually failing. Replacing crushed and disconnected flex branches off a sound sheet metal trunk is a fraction of the cost of rebuilding the whole distribution system.
Return air. Undersized or single-point returns are the most common defect we find in homes of this vintage, and adding return capacity is real sheet metal work.
Attic runs. Two-story homes with upstairs supplies routed through the attic add labor and material compared with a single-level crawlspace layout.

If a quote gives you one lump number for "new ductwork" without naming which trunks, branches and returns are being replaced, ask for the scope in writing. That is the number you are actually comparing between bids.

Why ducts fail faster here than the equipment does

Puget Sound is hard on ductwork in ways that drier parts of the country are not.

Damp crawlspaces

South King County soil holds water. A vented crawlspace with a compromised vapor barrier runs humid most of the year, and that humidity does three things: it rusts sheet metal at the seams, it saturates duct insulation so it stops insulating, and it makes the crawl a comfortable place for rodents. Compressed, wet insulation on a supply trunk is a quiet, year-round energy leak.

Rodent and critter damage

It is unglamorous and extremely common. Flex duct is a soft target. One torn branch under a bedroom can make that room eight degrees colder than the rest of the house and the homeowner will blame the furnace for years.

Flex duct that aged out

Much of the 1980s and 1990s flex in these neighborhoods is past its service life. The inner liner tears, the outer jacket splits, and long unsupported runs sag into a series of air-killing dips between joists. Flex is fine when it is short, straight and strapped properly. Thirty-year-old flex that was hung loose on day one is not.

Original designs that were never great

Plenty of these houses were built with the minimum: one central return, undersized branches to the far bedrooms, and a trunk that was sized for a furnace that no longer exists. That is a design problem, not a wear problem, and no amount of sealing fixes it.

How to tell it's the ducts and not the furnace

Before you price a replacement system, check for these:

One or two rooms are always too hot or too cold while the thermostat room is perfect.
Dust comes back within days of cleaning, and registers have grey streaking around them.
The system runs long cycles but the far end of the house never catches up.
You can see crushed flex, disconnected boots, torn jacket or rusted seams in the crawlspace.
The ducts are more than 20 to 25 years old and have never been inspected.
Rooms over the garage or at the end of a long run are the worst performers.

If two or more of those are true, the ducts are a live suspect. A technician can pull the crawlspace hatch and tell you in half an hour — and that costs you nothing as part of a free estimate visit.

City by city, what we actually find

Kent

Kent is the most mixed of the three. East Hill and West Hill split-levels and ramblers almost always have ducted systems already, with a crawlspace trunk and attic branches upstairs. Valley-floor properties and older manufactured homes are a different animal — belly ducts in a manufactured home are frequently the real problem, and replacing them is a specialized scope. State energy code lists a 21°F winter design temperature for the Kent area, so the distribution system has to deliver on the coldest mornings, not just the average ones.

Auburn

Auburn has the mildest winter design temperature in our entire service area at 25°F, which is good news for equipment sizing and takes some pressure off marginal duct runs. What it does not take pressure off is summer. Undersized returns show up most painfully in cooling, when the system has to move more air to move the same comfort. A lot of Auburn duct calls are really return-air calls.

Federal Way

We are headquartered on S 344th St, so this is home turf. Federal Way housing skews heavily to 1970s-1990s ramblers and split-levels with existing ductwork in reasonable condition — which is why most installs here stay simple and finish in one day. The exceptions are Dash Point and Redondo, where damp, salt-influenced air near the water accelerates corrosion on metal everywhere, ducts included. Design temperature is 24°F.

Repair, seal, or replace

The honest answer is that most homes do not need a full replacement.

Seal and repair when the trunk is sound, the problems are localized leaks and a few failed branches, and the room-by-room airflow is close. This is the cheapest meaningful upgrade in HVAC and it frequently fixes the complaint.

Modify when the layout is the problem — a bedroom with no return path, a bonus room on the end of a 40-foot run, a trunk that needs a proper takeoff. Targeted sheet metal work beats replacing everything.

Replace when the system is 25-plus years old, the insulation is soaked, the flex is failing in multiple places, or you are converting to a ducted heat pump and the existing ducts cannot move the airflow a heat pump needs. Heat pumps deliver a larger volume of cooler air than a gas furnace, which is exactly the condition that exposes undersized returns.

Bundle it with the equipment and save a trip

If you are already replacing a furnace or installing a heat pump, do the duct work at the same time. Same crew, same permit, same inspection, one disruption to your house. Equipment installs are typically a one-day job; adding a modification pushes it to one to two days, and a full duct replacement runs two to four days.

On rebates: local utility rebates attach to qualifying heat pump equipment, not to duct-only projects. The amount depends on what is being replaced and the equipment installed. Programs change, and utility programs pay only through their own contractor networks — so we read the utility off your bill, confirm what it currently pays, and file the paperwork. We do not quote a rebate figure we have not verified for your address.

What's included, and what the permit is for

Every Varsity duct job includes commercial-grade, custom-fabricated sheet metal where sheet metal belongs, properly supported and sealed connections, correct insulation values for crawlspace and attic runs, a permit pulled with your city, and the inspection scheduled. Kent, Auburn and Federal Way each issue their own mechanical permits. Skipping that step can complicate an insurance claim or a future sale — Washington's seller disclosure form asks directly about unpermitted work.

Installations carry a 10-year parts and labor warranty. License VARSIHC766RJ, $2M general liability, owner-operated out of Federal Way.

Get a real number for your house

Ductwork is the one part of an HVAC quote that genuinely cannot be priced from a phone call — somebody has to get in the crawlspace. Want a ballpark on equipment first? The instant estimate tool gives you Good, Better and Best starting prices in about 60 seconds. When you are ready for the real scope, book a free in-home estimate or call (253) 785-4622, Monday through Friday, 8 to 6. If you are local to us, the Federal Way ductwork page has the city-specific details.

We will tell you if sealing and a couple of branch replacements will fix it. That is usually the answer, and it is usually the cheap one.