A lot of the housing through the older parts of Missoula was built without ductwork. The Slant Streets, the University District, the Northside: plenty of those homes were heated with radiators, gravity furnaces or wall units, and forced air was never part of the plan.
If you own one, at some point you will face this question. Add ductwork so you can run a conventional furnace and central air, or go ductless.
There is a real answer, and it depends on your house.
What retrofitting ductwork actually involves
Duct is bulky. A main trunk needs real space, and branch runs need a path to every room you want to condition. In a house that was framed without any of that in mind, those paths have to be created.
In practice that means some combination of soffits dropped in ceilings, a closet or two given up to a chase, walls opened and closed again, and drywall and paint work afterwards. In a two-storey house the second floor is the hard part, because the path from the mechanical room up is rarely obvious.
None of this is exotic and none of it is impossible. It is just expensive, and a meaningful share of the cost is carpentry and finish work rather than HVAC.
There is also a permanent cost people underestimate: the space. A dropped soffit in a 1920s house with nine-foot ceilings is one thing. The same soffit in a house with eight-foot ceilings changes how the room feels, and you do not get that back.
What ductless involves instead
A mini-split needs one penetration through an exterior wall, roughly three inches across, for the line set between the outdoor unit and each indoor head. That is the whole intervention.
The trade is that you see the indoor head. A wall unit sits high on the wall and it is visible. Some people mind that a great deal and some do not notice it after a week, and it is worth being honest with yourself about which you are before you commit.
If you do mind, there are options. Floor-mounted units sit low against the wall like a radiator and read as furniture. Ceiling cassettes recess into the ceiling so only the grille shows. Short-run ducted heads hide an air handler in a soffit or closet and feed two or three rooms through a very short duct run, which gets you the ductless efficiency with nothing visible but a grille.
That last option is the one people do not know exists, and it is often the answer for a bedroom wing where appearance matters.
How to tell which way your house goes
Ductless is usually right when: the house has no usable ductwork at all, the finishes are good and you do not want them disturbed, you only really need to condition part of the house, you have a specific problem room, or the house is a candidate for zoning because different parts of it get used at very different times.
Ducted is usually right when: you already have ductwork in reasonable condition, you are gutting the house anyway for other reasons, you are building an addition where the runs can be designed in from the start, or the house is a straightforward single-storey with an accessible basement or crawlspace where the runs are easy.
It is genuinely a toss-up when: you have partial ductwork covering some of the house. That case comes down to the specifics, and it is worth having somebody look at what is actually there before deciding.
The one that is almost never worth it
Building a full duct system into a finished two-storey house purely so you can add air conditioning.
The cost of the ductwork usually dwarfs the cost of the equipment, and you spend it on infrastructure rather than on comfort. A multi-zone ductless system gets you cooling and heating for less, without the demolition.
The middle path nobody mentions
You do not have to pick one for the whole house.
Plenty of Missoula homes end up with a gas furnace serving the main floor through the ductwork that already exists, plus one or two ductless heads handling the finished attic, the addition, or the room over the garage that the furnace was never going to reach properly.
That is not a compromise. It is frequently the least expensive correct answer, and it is what we end up recommending more often than either extreme.
Get someone to look at it
None of this can be settled from a photo or a phone call. It depends on the framing, the mechanical space, where the existing runs go, and what you actually want out of the house.
We do free estimates and we will tell you plainly which way we think your house should go, including when that means less work for us.