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Indoor Air Quality · HumidifiersFurnace Humidifier Installation
Furnace humidifier installation puts the humidifier on the furnace itself, so the whole house holds a comfortable winter humidity with nobody carrying a jug of water upstairs. A bypass unit installs for $500–$900, a powered unit for $700–$1,200, and a steam humidifier for $1,500–$3,000.
A furnace does not dry your house out. The cold air leaking in around it does. Outdoor air at −10°C holding every bit of moisture it can carry arrives in a 20°C living room at well under 15 per cent relative humidity, and the furnace simply warms it. That is where the static shocks, the gaps opening along hardwood seams, the cracked trim and the 4 a.m. dry throat come from, and no amount of turning the thermostat up fixes any of it. The target for an Ontario winter is roughly 30 to 40 per cent, backed off as it gets colder outside — ideal indoor humidity in winter has the sliding scale.
Which of the three types fits depends mostly on your mechanical room. A bypass humidifier is the cheapest and needs a duct loop between the supply and return plenums plus room to swing it, which the low basements in Burlington's 1950s–60s bungalows and the furnace cupboards in townhouses often do not have. A powered, fan-driven unit mounts straight onto the supply plenum with no bypass duct and puts out noticeably more, which is why it is the usual answer in a tight install or a larger two-storey. A steam humidifier boils its own water and does not depend on the furnace running at all — that makes it the only real option on a house heated by a heat pump or a hybrid dual-fuel system, where the burners may not light for weeks. Bypass vs fan-powered vs steam compares them properly.
The water feed is where a cheap installation shows itself. A saddle valve punched into a copper line is quick, and it weeps eventually — we tee into the cold line with a proper quarter-turn shutoff and run a dedicated feed. Halton and Hamilton water is hard, so the evaporator pad or the steam canister scales up faster here than the manuals assume, which is a maintenance item to plan for rather than a fault. Steam units are also electrical appliances: they draw real current and need their own circuit, and on a panel that is already full that is a cost worth knowing about before you choose one.
Control is the last piece and the one that decides whether you like the result. An automatic humidistat with an outdoor sensor — or the humidity control built into a smart thermostat — lowers the setpoint as the temperature drops, which is exactly what keeps the inside of your windows dry. Set to a fixed number all winter, any humidifier will eventually fog and drip on the coldest glass in the house; why windows condense in winter explains the limit. We install humidifiers as a standalone job or during a furnace replacement while the plenum is already open — book a visit and we will size it to the house.
Add a humidifier when
- Static shocks off doorknobs, carpet and the car every time the heating has been running
- Gaps opening at hardwood seams, cracked trim and mitres, or instruments that will not hold tune
- Waking with a dry throat, nosebleeds or split lips through January and February
- The house feels cold at 21°C, so the thermostat keeps creeping up and the gas bill with it
- A portable unit that needs refilling twice a day and scrubbing weekly to stay clean
How it works
Plenum space, return-duct access, clearance for a bypass loop, a place to tee the water and, for steam, whether the panel has a spare breaker.
Unit mounted and sealed to the plenum, drain run to a floor drain or pump, water teed with its own shutoff, humidistat and outdoor sensor wired.
We set the winter setpoint, show you the damper flip for spring and autumn, and show you how the pad comes out so the annual change is a two-minute job.
Brands: We fit bypass, powered and steam humidifiers to every furnace brand we service — Lennox, Carrier, Trane, Goodman, Rheem, York, Amana, KeepRite, Daikin and Napoleon — including builder-installed units.
Common questions
What humidity should I run in winter?
Around 30 to 40 per cent in mild weather, dropping toward the bottom of that band or below during a deep cold snap. The right number is the highest one that leaves your windows dry, and older single-pane or aluminum-framed windows force it lower than modern triple glazing does.
Will a humidifier cause mould or window condensation?
Only if it is left at a fixed setting through a cold snap. An automatic humidistat with an outdoor sensor drops the setpoint as the temperature falls outside, which is the whole point of putting the humidifier on the furnace rather than running a portable. Treat fog on the coldest window in the house as the signal to back the setpoint down a few points, not as a reason to give up on the humidifier.
How much maintenance does it need?
A bypass or powered unit needs a fresh evaporator pad each autumn, at $20–$40, and the bypass damper flipped between the winter and summer positions. Steam units need their canister or cleaning cycle attended to more often on hard water. We do the pad during the fall furnace tune-up if you are on a plan.
My existing humidifier does not seem to do anything.
The usual culprits are a solenoid valve that has stopped opening, a saddle valve seized shut, a pad cemented solid with scale, or the bypass damper left in the summer position since last spring. Why a furnace humidifier stops working runs through them in order, and any of the four is a small repair rather than a replacement.
Can I add one to a heat pump or an electric furnace?
Only a steam unit, reliably. Bypass and powered humidifiers evaporate water into warm supply air, and a heat pump's supply air is not warm enough to do much with, so a steam humidifier that makes its own vapour is the one that works. How much a whole-home humidifier costs covers the price difference.