The furnace picks its moment. It’s the first properly cold morning in Courtenay, the house won’t come up to temperature, and you’re in the crawlspace with a flashlight trying to work out whether you’re looking at a small fix or a big cheque.
That question has a real answer, and you can get most of the way to it before anyone opens a toolbox. A single failed component and a furnace at the end of its working life leave different fingerprints — and knowing which one you’re looking at keeps the decision yours.
The short answer — when a repair still makes sense
Repair is usually the right call when the furnace is heating properly the rest of the time and the fault is a single component. Gas furnaces tend to fail at a component rather than all at once. Most fixes are a thermocouple, thermopile, igniter, or gas valve — parts that are replaceable, available, and don’t require touching the rest of the system.
If your furnace has been steady for years, has had no other faults, and has failed once in a way that traces back to one component, repairing it is the sensible move. There is no reason to replace a working heat exchanger because an igniter gave out.
Replacement earns its place when the failures start stacking up — when you’re calling about the same appliance more than once a season, when the fault is in the heat exchanger itself, or when the unit is old enough that parts are getting hard to source. At that point you’re not choosing between a repair and a replacement. You’re choosing between a replacement now and a replacement in January.
The signs that you’re in that second group show up long before the furnace quits.
Five signs your furnace is telling you something
None of these on their own means “replace it.” Together, they build a picture.
1. It’s running much longer to hit the same temperature. A furnace that used to cycle now runs almost continuously in shoulder season. That’s usually efficiency dropping off, and it shows up on the gas bill before it shows up as a breakdown.
2. Some rooms never get warm. Uneven heat can be a duct problem rather than a furnace problem — but if it’s new, and nothing about the house has changed, the furnace is worth looking at.
3. The noises are new. A furnace that bangs on startup or rattles at the burner is telling you something specific. When your unit won’t fire, loses pressure, bangs, or shuts down on safety, that’s a diagnostic call, not a wait-and-see.
4. You’re calling about it more than once a season. One repair is a repair. Three repairs is a payment plan on an appliance you’re going to replace anyway.
5. Parts are getting hard to find. This is the quiet one. When a gas fitter tells you a part is on backorder or has to be substituted, the appliance has aged out of easy support — and the next failure will take longer to fix.
The same question comes up with the other big gas appliance in the house — our guide to water heater maintenance and replacement works through the same call for a hot water tank.
What a furnace repair actually involves
A repair visit starts with diagnosis, not parts. The gas-side components get checked in order — burner, ignition, gas valve, venting, safety controls — and the fault gets traced before anything is swapped. A pilot and burner clean, thermocouple and igniter check, gas valve test, and venting inspection covers most of what goes wrong on a residential gas furnace.
That matters because a misdiagnosed furnace gets a new part and fails again on the same fault. Diagnosis first is slower on the day and cheaper over the winter.
What actually drives the cost of a new gas furnace
If the diagnosis points at replacement, the next question is always cost — and there’s no honest single number, because a furnace replacement isn’t one line item. Five things move the price, and they move it a lot:
Efficiency tier. A condensing furnace costs more up front and less to run. It also vents differently, which affects the install.
Sizing. This is the one homeowners skip and it’s the one that matters most — more on it below.
Venting. High-efficiency units produce condensate and vent differently from older mid-efficiency furnaces. If you’re moving from one to the other, the venting and the condensate drain both change, and that’s real work.
Gas supply. The existing gas line may or may not be sized for the new unit. Gas supply gets checked as part of any furnace installation, and if it needs upgrading, that’s part of the job.
Permit and inspection. Gas work in BC is permitted work. That’s not optional and it’s not a line item worth shopping around on.
The only way to get a real number is to have someone look at the actual appliance, the actual venting, and the actual gas supply in your actual house. That’s what a free estimate is for. You get clear pricing before the job starts — no surprises on the invoice.
What the efficiency numbers mean in a BC home
Furnace efficiency is measured as AFUE — the percentage of the fuel that ends up as heat in your house rather than out the vent.
Older power-vented furnaces sit in the 78–84 AFUE range. Condensing furnaces run 90–98 AFUE — and under Canada’s Energy Efficiency Regulations, a standard residential gas furnace manufactured on or after July 3, 2019 has to hit a minimum of 95% AFUE. So if you’re replacing a mid-efficiency unit, you are moving up a tier whether you planned to or not — and the floor is higher than a lot of the advice online still says it is.
Above that minimum, ENERGY STAR certification is the next step: an ENERGY STAR certified forced-air furnace fuelled by gas uses 6% less energy, on average, than a standard model. On the coast, where the heating season is long but rarely brutal, that difference compounds over a lot of mild months rather than a few extreme ones.
Sizing matters more than brand
Efficiency is the number on the sticker. Sizing is the number that decides whether you like living with the furnace — and it’s the one that gets rushed.
An oversized furnace short-cycles: it blasts, hits the thermostat, shuts off, and the house swings between too warm and not warm enough. That swing is the thing homeowners actually notice day to day, and it traces back to the sizing rather than to the brand on the front.
The correct method is a heat loss calculation on the actual house, done to the CSA F280 standard. Natural Resources Canada is blunt about the alternative: “A calculation based only on the floor area of the home or on replacing the furnace with one of ‘equivalent’ size is not adequate in most cases.”
In practice that means the fact your old furnace was a certain size is not, by itself, a reason for the new one to be. Houses get insulated. Windows get replaced. Additions get built. The number should be recalculated.
Who is allowed to do gas work in BC
Gas work is regulated in British Columbia, and furnace installation is gas work.
Per Technical Safety BC, gas installation permits are required for licensed contractors installing regulated gas equipment or gas systems. That means the person doing the work holds a gas licence, the job gets permitted, and the installation is done to code rather than to whatever was there before.
Siegfried Plumbing & Gas works to that standard. Red Seal certified journeyman plumber and gas fitter. Fully insured and WorkSafeBC covered. All work completed to BC Plumbing Code. Sized to your home, gas supply checked, venting installed to spec, condensate drain set, and the unit started up and calibrated — that’s what a proper installation looks like, and it’s why the permit exists.
A Comox Valley note on timing
If your furnace made it through last winter but you didn’t love how it behaved, now is the window.
Shoulder season is when this work goes smoothly: the house doesn’t need heat while the swap happens, the schedule has room, and nobody is deciding on a furnace in a cold living room in January. And if the answer turns out to be “this one’s got plenty of life left in it,” a free estimate is what it cost you to find that out.
Same-day service is available, 7 days a week, 8am to 6pm, across Courtenay, Comox, Cumberland, Royston, Union Bay, Fanny Bay, Merville, Black Creek, and Campbell River.
Don’t see your area listed above? Call and ask — chances are we’ll still cover you.
Furnace FAQ
How do I know whether to repair or replace my furnace?
If the furnace is otherwise heating well and the fault traces to one component — an igniter, a thermocouple, a gas valve — repair it. Repeat calls on the same appliance, a fault in the heat exchanger, or parts becoming hard to source usually point to replacement instead. A diagnostic visit tells you which one you’re in.
Do I need a permit to replace a gas furnace in BC?
Yes. Gas installation permits are required for licensed contractors installing regulated gas equipment or gas systems in British Columbia. The permit is pulled as part of the job.
What efficiency should I be looking at?
Canada’s Energy Efficiency Regulations set the minimum at 95% AFUE for a standard residential gas furnace manufactured on or after July 3, 2019 — so every new unit sits in the condensing range. ENERGY STAR certified models go further: a gas forced-air furnace with that certification uses 6% less energy on average than a standard model.
Can you just put in the same size furnace I had before?
That’s the shortcut, and it’s usually the wrong answer. The size should come from a heat loss calculation on your house as it is now — insulation, windows, and additions all change the number.
Do you charge for an estimate?
No. Estimates are free, and you get clear pricing before the job starts — no surprises on the invoice.
A furnace that’s acting up doesn’t have to be a crisis, and it doesn’t have to be a guess. Book a diagnostic and you’ll get a straight answer on whether you’re looking at a part or an appliance — and a free estimate either way.
Licensed, insured, and WorkSafeBC covered. All work completed to BC Plumbing Code. Same-day service, 7 days a week, 8am to 6pm.