Winter in Ontario almost always makes indoor air feel drier. You might notice dry skin, a scratchy throat, or static shocks. But if you add too much humidity, you can end up with foggy windows, water on sills, and even mould risk around cold corners.
So what’s the best humidity level for a home in winter? For most homes in Toronto and across Ontario, a realistic target is 30% to 40% relative humidity (RH), then adjust based on window condensation and outdoor temperature. Learn more about building comfort into the plan from day one: https://xavieras.ca/
Quick answer: What should humidity be in a house in winter?
- Start at ~35% RH
- If you see window condensation, drop humidity by 3–5% and re-check for a few days
- During very cold stretches, many homes do best around 25%–35% RH to keep windows dry
If you’re budgeting upgrades like new windows, insulation, or HVAC, this guide can help: Custom home building costs
Why indoor humidity drops in winter
Cold outdoor air holds less moisture. When that air leaks in (or comes in through ventilation) and gets heated, the relative humidity falls, even if the amount of water vapour didn’t change much. That’s why your home can feel dry the moment heating season starts. If you’re improving airtightness, be sure ventilation is planned properly too
The “best” winter humidity range in Ontario
A practical winter range for comfort without creating moisture problems is:
- 30%–40% RH for typical winter days
- 25%–35% RH during cold snaps (especially if you’re seeing window fog or ice)
Many articles say “35%–50% all winter,” but in real Toronto winters, 50% is often too high for a lot of homes—especially homes with older windows or colder exterior walls. If you’re considering renovations that affect the building envelope, plan it the right way
A simple humidity guide based on outdoor temperature (rule of thumb)
Every home is different, but this works well as a starting point:
- 0°C to -5°C: ~35%–40% RH
- -5°C to -15°C: ~30%–35% RH
- Below -15°C: ~25%–30% RH (to reduce condensation risk)
If your windows stay clear, you can usually stay near the higher end of the range for comfort. If your windows fog up, the right move is almost always to lower humidity and improve ventilation/airflow. If you’re planning a major project, permits may apply depending on scope: Understanding Building Permits in Toronto
Why windows get condensation (even when humidity “seems normal”)
Condensation isn’t caused by humidity alone—it happens when warm indoor air hits a surface that’s cold enough for moisture to turn into water droplets. In winter, windows are usually the coldest surfaces, so they show the problem first.
This is why one home can handle 40% RH with no issues, while another home gets wet windows at 35% RH. Window quality, airflow near the glass, and insulation details all matter. If you’re designing a new build, window selection should be part of the performance plan—not an afterthought
Signs your humidity is too low
If your RH is often under ~30% in winter, you may notice:
- dry skin, lips, irritated eyes
- sore throat in the morning
- nosebleeds
- static shocks
- wood floors or trim looking more “gapped” than usual
If you’re already experiencing comfort issues, it’s worth reviewing your home’s ventilation and airflow strategy too
Signs your humidity is too high (winter edition)
If your RH is too high for your home’s current windows/envelope, you may see:
- foggy windows in the morning
- water droplets on glass or window frames
- ice at the bottom corners of windows
- musty smell near exterior walls/closets
- recurring mildew around window trim
How to measure humidity properly
Before changing anything, use a simple digital hygrometer. Guessing based on “how it feels” often leads to over-humidifying (and window problems).
Place it:
- in a main living area
- around chest height
- away from vents, direct sunlight, kitchens, and bathrooms
How to lower humidity and stop window condensation
If windows are wet, start here:
- run bathroom fans longer (during and 20–30 minutes after showers)
- use the range hood while cooking
- make sure your HRV/ERV is running and set correctly (if you have one)
- improve airflow at windows (open blinds a bit, keep furniture away from exterior walls)
- monitor basement humidity (it can drive moisture upward)
Final takeaway
For most Toronto and Ontario winters, the best humidity level to aim for is 30%–40% RH, starting around 35%, then adjusting based on window condensation and outdoor temperature. Measure with a hygrometer, change settings gradually, and use ventilation to manage moisture at the source.
People Also Ask questions
Is 40% humidity too high in winter?
Not always. In many Ontario homes it’s fine—unless you’re seeing window condensation. If windows fog up, lower RH in small steps until it stops.
Is 50% humidity too high in winter?
Often, yes—especially during colder weather or with older windows. It commonly leads to condensation risk in many homes.
What’s the healthiest humidity level for a home?
A common general indoor target is around 30%–50% RH, but winter performance is limited by condensation risk—so the “best” winter number is usually the highest RH your home can handle without wet windows.
