SD&G has more pre-1900 stone and brick homes per capita than just about any region in Ontario outside of historic Kingston. Williamsburg, Morrisburg, Iroquois, and parts of Cornwall and Alexandria are full of Loyalist-era stone houses with foot-thick walls, original window openings, and HVAC that's been bolted onto buildings that were never designed for it.
We work on these homes all the time. The conventional answer — drop in a forced-air furnace and central AC — is often the wrong answer. Ductless mini-splits are frequently the right one. Here's why, and when.
Why forced-air is a mismatch for these homes
A typical century stone home was built around one of two heating strategies:
- Wood stoves in multiple rooms with passive ventilation
- Radiator-based hydronic heating added in the early 1900s
In both cases, the home was designed so that each room had its own heat source and could be independently warm or cool. The thick stone walls have thermal mass that buffers temperature swings — once a room is warm, it stays warm. Once a room is cool, it stays cool.
When you bolt a forced-air system into one of these homes, three problems show up:
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Ductwork has nowhere to go. Stone walls can't be opened easily; floor joists may already be cut for other systems; ceiling drops eat headroom that 8-foot rooms can't spare. The duct runs that do get installed tend to be undersized, long, and inefficient.
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The thermal-mass mismatch. Forced-air responds quickly to thermostat changes; stone walls don't. You end up with hot-cold cycles where the air temperature swings 4-5°C in each cycle while the wall mass stays stuck at one temperature, creating perpetual drafts as air convects across temperature differences.
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One-zone control across very different rooms. Stone homes have rooms with totally different solar exposure, mass, and use patterns. The south-facing front parlour overheats in afternoon sun; the north-facing back kitchen is always cold. A single forced-air zone can't solve this without major ductwork investment.
Why mini-splits map well
A ductless mini-split system is one outdoor compressor unit serving 2-8 indoor "head" units mounted on walls or ceilings inside the home. Each indoor head is its own zone with its own thermostat.
For a stone home, the advantages stack up:
- No ductwork required. The only thing penetrating the wall is a 3-inch hole for a refrigerant line set and a drain line.
- Per-room zoning by default. The south-facing parlour and the north-facing kitchen each get their own head, set independently.
- High-efficiency heat pump heating. Modern mini-splits are cold-climate rated and provide useful heat down to -25°C, perfect for replacing or supplementing the existing heating system.
- Free AC built in. The same unit provides cooling in summer — often the first central AC the house has ever had.
- Minimal aesthetic impact. Indoor heads are unobtrusive compared to ductwork drops or window units, and modern designs are much less visually intrusive than the early 2000s models.
When mini-splits aren't the right answer
To be honest about it, mini-splits don't fit every situation:
- If you want fully invisible HVAC, ducted high-velocity systems (Unico, SpacePak) hide better but cost dramatically more.
- If the home is very large (5,000+ sq ft) and you want full whole-home conditioning, the head count gets unwieldy and a hybrid system may be better.
- If you want a single thermostat for the whole house, mini-splits give you the opposite of that — every room is its own zone with its own remote. Most stone-home owners come to prefer this once they have it, but it's a real difference.
A real example
Take a typical Williamsburg stone home — say 1,800 sq ft on two floors, built around 1860, currently heated by a propane boiler feeding cast-iron radiators upstairs and a wood stove insert in the main fireplace. No AC.
The conventional quote: rip out the radiators, install ductwork in dropped ceilings, central forced-air furnace and AC. Cost: $20,000-$30,000 plus extensive interior renovation. Result: the home heats and cools but loses character, gains hot-cold cycling, and the duct chases reduce ceiling heights in two rooms.
The mini-split alternative: keep the existing boiler as backup, install a 5-zone mini-split system (one head per major room). Cost: $14,000-$18,000. Result: per-room comfort, AC where there was none, no interior renovation, the radiators stay in place as a redundant heat source.
For most stone homes, the mini-split version wins on cost, on aesthetics, and on comfort.
What we look at on the assessment visit
When we come out to quote a stone-home mini-split:
- Heat-loss calculation per room — sizes the system correctly so each head matches the room's load
- Outdoor unit placement — where can the compressor go without being eyesore or noise problem
- Line set routing — the path from outdoor unit to each indoor head, minimizing wall penetrations and visual impact
- Electrical capacity — most stone homes have older panels that may need upgrades
- Backup heating strategy — what happens if the heat pump system needs service mid-winter? Often the existing boiler or wood stove serves as redundancy, which is reassuring.
Cost ballparks
For SD&G stone homes specifically:
- Single-zone (one room or one small open area): $4,000-$6,500
- 2-3 zone: $7,000-$12,000
- 4-5 zone: $12,000-$18,000
- 6+ zone whole-home: $18,000-$28,000
Federal Greener Homes Grant and IESO rebates often reduce these by $4,000-$7,000 for cold-climate certified units, putting the net cost in a similar range to a conventional furnace + AC install but with much better comfort outcomes.
What about the existing boiler/radiators?
We almost always recommend keeping them in place as a backup heating system. Removing the boiler infrastructure is expensive (it's bolted into the basement floor, the chimney needs decommissioning, the pipes need to be cut and capped) and the residual value as backup heat is real. If your mini-split system ever has an issue mid-January, you fire up the boiler and you're warm.
Next step
If you have a stone or brick home in Williamsburg, Morrisburg, Iroquois, Alexandria, or anywhere else in our service area, give us a call or request an assessment. We'll come look at the specific house, talk through what would work, and give you honest options — including telling you when a mini-split isn't the right call.
See also: our ductless mini-split and heat pump service pages.