Too Dry or Too Wet? Health Canada’s Winter Humidity Range

Dry windows and comfortable air pull in opposite directions in a Canadian winter. Drop the humidity enough to stop the dripping and someone in the house starts complaining about dry skin and static. Health Canada’s guidance shows where the balance sits.

The numbers

• General range: Health Canada’s current indoor air quality pages and Healthy Home Guide say to keep relative humidity between 30% and 50%.
• Winter: Health Canada’s Relative Humidity Indoors factsheet recommends 30–35% in winter and below 50% in summer.
• Dust mites: Health Canada’s dust-mite page recommends 35–50%.

Why not lower, or higher?

Below 30%, the factsheet warns, dry air may aggravate skin allergies and cause eye irritation and respiratory infections. It can crack skin, increase static, help some viruses survive, and make wood floors and furniture shrink.

Above 55%, the building and its contents can stay damp for long periods, which promotes mould, bacteria, and dust mites. Health Canada’s mould guide recommends running a dehumidifier when RH is above 50% or moisture is condensing on cold surfaces like window panes.

Putting it together for windows

1. Measure first. A hygrometer tells you whether you’re actually dry or just feeling it.
2. Aim for 30–35% on cold winter days. That’s Health Canada’s winter range, and it’s usually low enough to keep decent windows dry. On the coldest nights or with older windows, the glass may still sweat. CMHC notes 30% or lower may be needed in very cold weather.
3. If it’s below 30% and uncomfortable, Health Canada says a humidifier can bring it back to about 30–35%. Maintain it per the manufacturer, and turn it down if you see excessive condensation on cold surfaces.
4. If windows are wet, Health Canada’s mould guide says to use exhaust fans and the range hood, keep window coverings open so warm air reaches the glass, dry frames and sills daily, and unplug humidifiers.

Older NRCan material cites an earlier Health Canada winter range of 30–55%. The current Health Canada pages use 30–50% overall and 30–35% for winter, so this site follows those.

Sources: Health Canada, Relative Humidity Indoors factsheet; Health Canada, Guide to addressing moisture and mould indoors; Health Canada, Improve indoor air quality in your home; Health Canada, Dust and dust mites; CMHC, Moisture and Air.

Originally published at https://dry-glass-notes.surge.sh/articles/health-canada-winter-humidity-range.html (AI-assisted, sources cited). If this helped, zaps go to hollisvarrow3753@coinos.io.