WINTER COMFORT · HUMIDITY
What should indoor humidity be in winter?
The heating is on. The room feels dry. But the windows are wet. Before turning up a humidifier, look at both the air reading and the coldest surfaces.
Published · HOMENVIRO · For cold-weather homes
READING + OBSERVATION
What do your reading and window show?
Repeatedly below 30%; surfaces dry
Check the meter and another location. If the low pattern holds, try a low humidifier setting and check the windows the next morning.
30–50%; surfaces dry
Keep the current routine. There is no need to chase 50% just because a device can reach it.
Window or wall is wet at any reading
Turn down added moisture, wipe the surface and check ventilation and moisture sources. If it keeps returning, investigate the cold surface or a leak.
Repeatedly above 50%; no humidifier
Look for moisture from showers, cooking or laundry. Use suitable extraction, compare the next few days and seek a building assessment if dampness persists.
No meter yet? Start by checking whether surfaces are wet morning and evening, then measure before buying a humidifier.
Why the number falls when the heating comes on
Relative humidity describes water vapor relative to the saturation level at the current temperature. When cold outdoor air enters and warms up without added water, its relative humidity falls. Heating has not necessarily extracted water like a dehumidifier. Natural Resources Canada explains this winter drying effect; it also notes that tighter homes can retain more of the moisture produced indoors.
Why dry-feeling air and wet glass can coexist
A hygrometer in the middle of a warm room does not measure conditions at a cold window edge. The surface may be cold enough for water to condense even when the room’s average reading looks unremarkable. Curtains, glazing and local airflow can change the pattern. A wet window is a reason to look closer, not proof that the entire room has the same humidity.
A THREE-DAY CHECK
Measure, change one thing, compare
- Day 1: note morning and evening readings, wet surfaces and moisture-producing activities.
- Day 2: use the matching action above. Change one setting or routine, then observe the same locations.
- Day 3: compare readings and window edges. Keep a helpful change; if condensation or damp patches persist, inspect ventilation, cold surfaces and possible leaks.
These are starting points for investigation, not a guarantee against mold. Local climate and the building’s condition matter.
Measure before buying a humidifier
Try a simple three-day log: note the temperature and humidity after waking, in the afternoon and before bed. Put the meter in a representative occupied area, away from direct mist, a heater or an open window. Follow its placement instructions. Record showering, laundry and humidifier use alongside the reading. The pattern is more useful than one number taken just after airing.
If you add moisture, make it adjustable
Use a low setting first and recheck the room and window edges. EPA advises against humidifying above 50% and recommends reducing output if nearby surfaces become damp. Empty, dry and refill portable units daily; clean them according to manufacturer guidance and EPA recommendations. Low-mineral water helps limit mineral dispersal from ultrasonic units. A clean-looking tank is not a reason to skip maintenance.
If the room is too damp, start with the source
Health Canada recommends ventilation to remove indoor moisture and identifies winter window condensation as a warning sign. Use appropriate extraction during moisture-producing activities and keep the home’s ventilation system maintained. A persistent wet patch may need leak investigation or a building repair. Simply buying a dehumidifier does not establish why the moisture is there.
Does every bedroom need a humidifier in November?
No. November is a planning cue for colder regions, not a universal instruction to add water. Compare the room’s measurements with what is happening at its surfaces. A home in a damp climate and a heated home in a dry continental climate may need different actions in the same month.
Your first useful step tonight
Write down the room reading, check the window edges and photograph any recurring wet area. Make one small adjustment and compare the next morning. If the readings and visible conditions keep disagreeing, check the meter and investigate the room rather than repeatedly increasing or decreasing the setting.
SOURCES & SCOPE
Researched household guidance, not a product test or an individual medical recommendation. Sources checked 20 October 2026: U.S. EPA: Care for Your Air; U.S. EPA: use and care of humidifiers; Natural Resources Canada: how your house works; Health Canada: ventilation and the indoor environment. The observation log and decision prompts are HOMENVIRO’s practical synthesis.