The quick answer
Quick answer
If your home already has a boiler and radiators, keeping and modernizing the hydronic system is usually the right call — radiant heat is the most comfortable heat there is, and a conversion means building a duct system your house was never designed for. Converting to forced air earns its price mainly when you want central air conditioning and whole-home air filtration riding on the same new ducts.
- Radiator heat is prized for a reason: steady, silent, dust-free warmth with no blowing air. Homes with hydronic heat rarely regret keeping it.
- The real product of a conversion isn't the furnace — it's the ductwork. Retrofitting supply and return ducts through a 1920s–1950s home is carpentry, chases, and lost closet space.
- Cooling is the honest reason conversions happen: ducts enable central AC and filtration. But ductless mini-splits now deliver cooling without sacrificing the boiler — read that comparison before deciding.
- We install, repair, and maintain boilers (no new-construction work) — so we make money either way and have no thumb on this scale.
- Boiler replacement is quoted per home; no published range yet. Furnace replacement runs $6,200–$10,600 — before any ductwork, which is the conversion's big variable.
The decision factors
What you'd give up
Hydronic heat doesn't blow air, doesn't stir dust, doesn't dry the house as aggressively, and holds temperature with flywheel steadiness. People who grew up with radiators describe forced air as 'gusty' for a reason. Comfort loss is the conversion's quiet cost.
Whether cooling is the actual goal
Most conversion conversations are secretly AC conversations. If summer comfort is what you want, price a ductless mini-split system alongside the conversion — it usually delivers the cooling for less disruption and leaves the radiators doing what they do best.
The duct retrofit reality
Ducts need cross-sections and routes. Older Waukesha and Milwaukee-area homes with plaster walls, balloon framing, and finished basements make every run a small construction project. Any conversion quote that doesn't walk the house room by room is guessing.
The boiler's actual condition
A tired boiler doesn't mandate conversion — modern condensing boilers are dramatically more efficient than the old cast-iron classics, and swapping boiler-for-boiler is a one-day job against a multi-day conversion.
Keep the boiler (hydronic) vs Convert to forced-air furnace
| What matters | Keep the boiler | Convert to forced air |
|---|---|---|
| Heat quality | Radiant, silent, steady — the comfort benchmark | Faster response, but blowing air, more temperature swing |
| Air conditioning path | Separate system (ductless mini-splits, typically) | Central AC rides the new ducts |
| Air filtration / IAQ gear | Limited to portable or ductless-level filtration | Whole-home filter, humidifier, UV all become options |
| Disruption to the house | One mechanical-room swap | Duct construction through walls, ceilings, closets |
| Humidity behavior | Doesn't dry the air as hard in winter | Forced air + Wisconsin winter usually means adding a humidifier |
| Freeze robustness | Water in pipes — needs heat on or glycol care in extreme scenarios | No hydronic piping to protect |
Old Wisconsin housing stock, honest advice
Southeastern Wisconsin has a deep bench of pre-1960 homes — Waukesha's older neighborhoods, Wauwatosa, West Allis, Milwaukee's first ring — where hydronic heat was the original equipment and the house was framed with zero thought for ductwork. In those homes, the radiators are usually the best heating system the house will ever have. Our default advice is to modernize the boiler when its time comes and solve summer with ductless heads in the rooms that matter.
The conversion still has its place: gut renovations where walls are open anyway, homes where a previous owner already added partial ducting, and owners who genuinely want the whole-home filtration and humidification that only a ducted system carries. In that case, insist on a room-by-room duct design — not 'we'll figure out the returns as we go.' Undersized returns are the number-one sin of retrofit forced air, and you'll hear it whistling for the next twenty years.
The honest numbers
One side of this comparison has a published planning range; the other is honest custom work.
| Option | Planning range | What that covers |
|---|---|---|
| Furnace replacement (equipment portion of a conversion) | $6,200–$10,600 | The furnace itself. A conversion adds full duct design and construction on top — quoted per home after a room-by-room walkthrough. |
| Boiler replacement / repair | Quoted per home | Boiler work is too configuration-dependent for an honest published range (cast iron vs condensing, zones, venting, indirect tanks). Written itemized quote after an on-site look. We install, repair, and maintain boilers — no new-construction projects. |
We don't publish dollar ranges we haven't verified for our own market. For these jobs you get a written, itemized quote after an on-site look — and you're welcome to put it up against anyone else's number with our free second opinion.
Which one should you choose?
Keep the boiler
Keep the boiler when
The radiators still heat evenly, the house was built around them, and your summer problem is solvable with ductless heads. Modernizing to a high-efficiency boiler preserves the best comfort in the business and skips a construction project. This is our default recommendation in hydronic homes, and we're the ones who'd profit from the bigger job.
Convert to forced air
Convert to forced air when
You're opening walls in a major renovation anyway, you want central AC plus whole-home filtration and humidification as a package, or the hydronic system has deep problems (failing buried piping, chronically uneven zones) that would cost boiler-replacement money to fix without fixing them. Then the conversion is honest value — priced room by room, in writing.
Also consider: boiler + ductless mini-splits
The hybrid most old-house owners actually want: keep radiant heat, add ductless heads for summer. Cooling without ductwork, no comfort downgrade in winter, and the mini-splits back up the heat in shoulder seasons. See the ductless vs central air comparison for how that half works.
Ready when you are
Get the answer for your house.
Both options priced in writing, sized to your home, explained without a pitch — 24/7, owner-operated, licensed (WI #1482483). Already have someone else's quote? We'll review it for free.
Keep exploring
Next steps
Honest answers, before you decide
Are boilers less efficient than furnaces?
Not inherently. Old cast-iron boilers running at 60–70% efficiency created that impression, but modern condensing boilers reach efficiency comparable to condensing furnaces. If your bills are high on an old boiler, the fix is usually a modern boiler — not a change of heating medium.
Can you even get parts for old boilers?
For most of the common cast-iron families, yes — circulators, zone valves, aquastats, and expansion tanks are standard trade parts. Truly obsolete sections or cracked castings are when replacement becomes the only sensible line item. We service what's serviceable and say so when it isn't.
Does converting to forced air help resale?
It cuts both ways, honestly. Some buyers want central air and see ducts as a plus; plenty of old-house buyers specifically prize radiator heat and read a conversion as a comfort downgrade. Central AC is the part buyers reliably reward — and ductless delivers that without touching the boiler. We wouldn't convert for resale alone.
Reviewed by Shane Herro, Owner & Lead Tech · Last updated 2026-07-14