What Is the Ideal Humidity Level for a Home?
The right humidity level helps protect both the comfort of your home’s occupants and its building materials. In Quebec, the general target is 30% to 50% relative humidity, but it may need to be lowered during extreme cold if condensation appears on the windows.
How to Measure Humidity
Place a hygrometer in the main rooms, away from heating vents, windows and sources of steam. Check the readings at different times of day over several days rather than relying on a single measurement.
Signs That Humidity Is Too High
Humidity refers to the amount of water vapour in the air. When humidity levels are too high or too low, several problems can arise:
- Too high: mould growth, increased dust mite populations, musty odours and damage to building materials.
- Persistent condensation on windows;
- A musty smell or stains on walls and ceilings;
- Blistering paint, swollen wood or a damp basement;
- Humidity that consistently remains above 50%.
Start by using bathroom exhaust fans and the kitchen range hood, keeping air vents clear, operating mechanical ventilation and addressing any water infiltration. A dehumidifier can help, but it does not replace fixing the underlying cause.
- Too low: irritated airways, dry skin and an increased risk of cracking in furniture or interior finishes.
- Nosebleeds;
- Itchy skin.
Below 30%, the air may become uncomfortable and some materials may dry out. Before adding a humidifier, however, check that condensation is not already forming on cold surfaces. Regularly clean any appliance that contains water.
Photo credit: Centris
Photo credit: Centris
How Can You Measure and Adjust Your Home’s Humidity?
To measure relative humidity in each room, use a hygrometer, an inexpensive and widely available tool. As a general guideline, maintain humidity between 30% and 50%. However, as outdoor temperatures fall, your home’s building envelope may require a lower level to prevent condensation. If water forms on the windows, gradually reduce humidity and improve ventilation. Persistent condensation, water infiltration or extensive mould growth should be assessed by a qualified building professional.
- In winter: aim for around 30%, adjusting downward during extreme cold if necessary to prevent condensation.
- In summer: keep humidity at or below 50%.
Solutions for Adjusting Humidity
To reduce humidity:
- Use a dehumidifier. Learn more here
- Check insulation and window seals for problems that could contribute to condensation or water infiltration.
- Regularly clean or replace ventilation and air-conditioning filters according to the manufacturer’s instructions.
- Excessive humidity can also indicate an underlying problem, such as a foundation drainage system, commonly called a French drain, that has reached the end of its useful life.
To increase humidity:
- Install a humidifier. Explore the options here
- Boiling water or hanging wet laundry indoors can increase humidity, but monitor the readings to avoid excess moisture and condensation.
- Houseplants can also contribute moisture to the air, although their effect varies.
The Benefits of Maintaining an Appropriate Humidity Level
Maintaining an appropriate humidity level offers several benefits:
- Greater comfort: helps limit the skin and airway irritation associated with excessively dry air.
- Protection of belongings: helps prevent humidity-related cracking or damage to furniture and artwork.
- Better control of indoor conditions: supports a more comfortable balance between heating, cooling and moisture management.
Monitor your home’s humidity regularly and make adjustments as needed to maintain a healthy, comfortable indoor environment.
Useful Resources
- Health Canada — Guide to addressing moisture and mould indoors
- Natural Resources Canada — Choosing the right dehumidifier
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