Humidifier seasonal care

Why Colorado homes need humidification

Cold outdoor air holds very little moisture. Heat it to room temperature and the relative humidity collapses. In a Colorado Springs winter, that routinely puts indoor relative humidity below 20% — drier than most deserts.

What that does inside a house is specific and recognizable: static shocks on every doorknob, hardwood floors and trim that shrink and crack, gaps opening at baseboards, furniture joints loosening, musical instruments drifting out of tune, dry sinuses and skin, and nosebleeds in winter.

It also makes the house feel colder than the thermostat reads, because dry air pulls moisture off your skin. People compensate by turning the heat up, which dries the air further. Humidifying properly often lets you hold a lower thermostat setting and feel the same.

Types, briefly

Whole-home humidifiers mount on the ductwork and come in a few common forms. Bypass units route some warm supply air across a wet evaporator pad and back into the return. Fan-powered units add their own blower, so they do not need the bypass duct and can add more moisture. Steam units boil water and inject vapor directly, which gives the most control and the most capacity but uses more energy and has its own maintenance.

The maintenance pattern is similar across all of them: a water-contacting part that scales up and gets replaced, a water supply that gets shut off for summer, and a control that needs setting correctly. Which type suits a house depends on its size, ductwork and how dry it actually runs.

Fall startup

Do this before the heating season, at the same time as the furnace filter.

• Shut off power to the furnace at the switch before opening anything.
• Replace the evaporator pad or canister. Pull the old one and look at it — on hard Front Range water it will be stiff with white scale. Pads are inexpensive and this is the step that makes the whole system work.
• Clean the housing. Wipe out mineral scale and any sediment in the base and distribution tray.
• Open the water supply valve you closed in spring, and check the saddle valve and supply line for drips.
• Open the bypass damper to its winter position. The damper is marked, and leaving it on the summer setting is the most common reason a humidifier "does not work."
• Confirm the drain line is clear and running to the floor drain or condensate pump.
• Restore power and run a cycle. Call for humidity at the humidistat and confirm water flows across the pad and down the drain.

Setting the humidistat

Start around 35% relative humidity. That is comfortable for most people and gentle on wood without overloading the building envelope.

Then let the house tell you. In very cold weather, the same indoor humidity that was fine at 30 degrees outside will condense on windows at zero. Some humidistats have an outdoor temperature compensation dial for exactly this; automatic models adjust on their own. Without one, you dial it down manually during cold snaps.

Keep a cheap hygrometer in a living area rather than trusting the humidistat's own reading, which sits in the ductwork and reads the duct, not the room.

Window condensation is the signal

This is the most useful feedback the house gives you. If moisture is forming on the inside of your windows, the humidity is too high for the current outdoor temperature. Turn it down.

What makes that important is not the windows themselves. Windows are the coldest surface in the room, so they condense first — which means they are an early warning for what is happening inside exterior wall cavities and attics, where you cannot see it. Moisture accumulating there causes rot and mold long before anyone notices. Glass fogging is cheap information. Act on it.

Summer shutdown

When the heating season ends, shut the system down rather than letting it sit. Close the water supply valve, set the humidistat to off, and move the bypass damper to its summer position so conditioned air is not short-circuiting through the bypass duct all summer.

Remove the pad or canister and discard it — it is at the end of its season. Wipe out the housing. A humidifier left wet and idle through a warm summer grows biofilm on the pad and in the tray, and that is exactly what you do not want upstream of your supply air. If indoor air quality is a concern in your house, this one is worth not skipping.

Troubleshooting the common complaints

• No humidity at all — bypass damper still on summer, water valve closed, or a scaled solenoid valve.
• Running constantly, humidity still low — pad badly scaled, leaky house envelope, or the unit is undersized.
• Water running continuously to the drain — a stuck solenoid valve.
• White dust on furniture — mineral content, most common with steam units on hard water.
• Musty smell when the heat runs — biofilm on a pad that was left in over summer.

What a licensed technician does that you can't

Pad swaps and valve positions are homeowner work. Sizing, wiring and water connections are not.

A licensed technician sizes humidification to the house's actual volume and tightness, which is the difference between a unit that keeps up in January and one that runs nonstop and never gets there. They wire the humidistat into the furnace control board correctly, so the humidifier runs only when the blower does. They install the saddle or tee connection on the water supply to code and test it for leaks.

They also assess whether high humidity is actually a ventilation problem rather than a humidifier setting, measure static pressure to confirm a bypass duct is not hurting system airflow, and inspect for moisture damage where humidity has been run too high. On hard Front Range water they can advise whether a treatment system would extend pad life across the whole house. And anything involving the furnace's gas or electrical side stays with a licensed trade.

Frequently asked questions