Why is ductless the go-to for Seattle's older homes?
Seattle's pre-war housing stock — Craftsmans, Tudors, foursquares across neighborhoods from Ballard to Burien — was built with radiators, gravity furnaces, or nothing at all, and retrofitting ducts through plaster walls and balloon framing is invasive and expensive. Ductless heads need a three-inch wall opening each, which is why they've become the standard comfort retrofit for this stock: heating and cooling without tearing the plaster, trim, and floor plan that make these houses worth owning.
The quick answer
- Pre-war homes rarely have usable ducts — and cutting ducts into plaster is a renovation, not an install
- Ductless preserves the plaster, trim, and floor plan that make these houses worth owning
- Watch the electrical panel: 60–100 amp services are common pre-war and may need an upgrade
- Oil-heated pre-war homes stack the Clean Heat rebate ($2,000–$6,000) on top of the retrofit
The pre-war heating situation
These homes heat by whatever era they last got attention in: original radiators, converted gravity 'octopus' furnaces, oil burners (Seattle still has an estimated 8,000–10,000 oil-heated homes), electric baseboards from a 1970s remodel, or wall heaters. Common thread: no ductwork, or ducts so old and leaky they're better abandoned.
And none of them cool. As heat events became regular Puget Sound features, the question for pre-war owners shifted from 'how do we heat better' to 'how do we do both without wrecking the house' — which is precisely the ductless proposition.
Oil-heated pre-war homes add another layer: Seattle still has an estimated 8,000–10,000 oil-heated houses, and the Clean Heat program ($2,000–$6,000 for qualifying conversions) stacks on top of the comfort upgrade. Ductless is often the distribution answer when there's no ductwork to reuse and no appetite for opening walls.
How a typical pre-war conversion goes
Design starts room by room: the load calculation maps where heat is actually needed, then head placement balances coverage against the house's bones — a head in the main living space, one per upstairs bedroom or a hallway compromise, floor consoles under windows where wall space is precious. The outdoor unit sits on a pad or wall brackets, sized for the total.
Line sets route along exterior walls in paintable channel, each penetration a sealed three-inch opening. Most installs run one to three days. The plaster never gets opened; the crown molding never moves. Old radiators can stay as backup or come out for space.
The two pre-work questions: panel and placement
Electrical first: pre-war homes commonly carry 60–100 amp service, and a multi-zone system needs a dedicated circuit with real capacity. Sometimes there's room; sometimes a panel upgrade joins the project — better discovered in the estimate than at install. (Full electrification often ultimately wants 150–200 amp service.)
Placement second: these houses have opinions. Historic trim, stucco, brick veneer — an installer who's worked this stock (we've been in these houses since 1938, with our own sheet metal shop when custom transitions are needed) routes line sets so the house still looks like itself.
Where old-home retrofits go sideways
Underestimating the envelope: original single-pane windows and uninsulated walls raise the load — honest sizing accounts for the house as it is, not as a spec sheet wishes. Sometimes the right first dollar is attic insulation, which shrinks the system the house needs.
Skipping the panel conversation until change-order day. And the aesthetic miss: line sets run carelessly across the front facade. All three are estimate-stage problems — which is why the estimate visit for a pre-war home should take real time, not ten minutes.
We've worked these houses since 1938, and the recurring theme is that the house tells you where heads can live — transoms, hallways, floor consoles under tall windows. Fighting the architecture with a generic head-in-every-room layout is how period interiors end up feeling like a hotel.
Questions Seattle homeowners ask
Will heads ruin the look of a period interior?
Handled carefully, no — placement above sightlines, floor consoles under windows, or slim ceiling cassettes in remodeled spaces all keep period rooms intact. It's a design conversation during the estimate, not an afterthought on install day. In Seattle Craftsmans especially, a single well-placed head in the main living space plus upstairs bedroom heads often covers the house without cluttering every wall.
Can ductless handle a drafty 1920s house in January?
Sized for the house as it actually is — yes. Cold-climate equipment holds full output far below Seattle temperatures; the engineering risk is under-sizing for a leaky envelope, which is what the load calculation prevents. Insulation upgrades shrink the required system and are worth pricing alongside. We've heated drafty West Seattle Tudors through January cold snaps — the math has to be honest, not optimistic.
What does a pre-war conversion cost?
Single-zone installs typically run $3,500–$6,000 in the Seattle market and multi-zone $6,000–$15,000 depending on zones and runs (published market ranges, not a quote). Panel work, if needed, is additional — and oil-to-heat-pump conversions can take $2,000–$6,000 off via Seattle Clean Heat.
Should the old radiators or furnace stay?
Oil equipment: decommission — the Clean Heat rebate requires it and the tank is a liability. Working radiators: owner's choice; some keep them as backup or for the aesthetic. Gravity furnaces: they're museum pieces occupying a basement — most owners reclaim the space.
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How we know this
Housing-stock patterns from Glendale's Seattle service history since 1938; panel and duct-retrofit context per regional electrification guidance (Seattle HVAC Authority, regional installers); rebate terms verified July 2026 (seattle.gov).
Reviewed by the Glendale Heating & Air Conditioning team · Last updated 2026-07-15
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