What Should Humidity Be in a House in Canada? Winter & Summer Guide

Quick answer: 30% to 50% is the range, not a magic setting

Health Canada’s current mould-prevention guidance recommends maintaining indoor relative humidity (RH) between 30% and 50%. That is the best simple starting point for a Canadian home.

But it is not a promise that 40% or 50% will work in every house on every January night.

Health Canada’s newer guidance for indoor-air professionals says to keep humidity below 50% in summer and around 30% in colder weather, depending on what the building envelope can tolerate without condensation. Natural Resources Canada (NRCan) makes the reason visible: the colder it gets outside, the less indoor moisture many windows can tolerate before the room-side glass begins to condense.

So the practical ReadyHome rule is:

Use 30% to 50% as the general range, then let the season, your hygrometer and what the house is actually doing refine the decision.

The federal references behind those distinctions are Health Canada’s guide to moisture and mould, its guidance for indoor-air-quality professionals, and NRCan’s Keeping The Heat In: Operating your house.

Home humidity checker

What does your humidity reading actually mean?

Give the checker your measured RH if you have it, then add the season and what the house is showing you. It uses Health Canada's general range plus conservative moisture-routing rules - not a fake universal "perfect humidity" score.

Indoor relative humidity (%)Leave this blank if you do not have a hygrometer reading yet.What conditions are you in?Choose oneHeating season / cold weatherMild shoulder seasonWarm or humid weatherWhat moisture pattern are you seeing?Choose the strongest signal, even if the RH number itself looks normal.Choose oneNo persistent condensation or dampnessMostly one window or one small cold areaMany windows are condensing or frostingBasement feels damp/musty or reads wetter than upstairsWater appears with rain, snowmelt, seepage, or an active leakIs visible mould already present?Choose oneNo visible mouldYes, visible mould is presentAre you intentionally adding humidity?Choose oneA portable or whole-house humidifier is runningNo humidifier is runningNot sureReset answers

Start with the reading and the pattern

Answer the observation questions to get a conservative next step.

No hygrometer yet? Leave RH blank. The checker will tell you to measure before it pretends your skin or static shocks are a precision instrument.

This is homeowner decision support, not a building-envelope inspection, HVAC commissioning report, mould assessment, or health diagnosis. Health Canada's 30% to 50% guidance is a general range; actual condensation risk depends on surface temperatures and building conditions.

What does relative humidity actually tell you?

Relative humidity is not simply “how much water is in the air.” It describes how close the air is to saturation at its current temperature.

That temperature part is why Canadian winter humidity gets confusing. Warm indoor air can contain the same amount of water vapour and show a much lower RH than that air would after it cools near a window, exterior corner or other cold surface.

Condensation begins when the air immediately beside a surface is cooled enough to reach its dew point. The centre of the room can therefore have a perfectly ordinary hygrometer reading while one unusually cold surface gets wet.

That gives you two different questions:

1. Is the room’s RH generally high, low or within the usual range? A hygrometer can answer that.
2. Are particular surfaces cold enough to condense at that moisture level? Your hygrometer cannot answer that by itself.

The window-condensation guide and checker goes deeper on dew point, room-side versus outside moisture, between-pane fog and local airflow around the glass.

What should indoor humidity be in winter in Canada?

A good winter starting point is still Health Canada’s general 30% to 50% RH range, but colder weather pushes the practical upper end downward in many homes.

Health Canada’s current professional guidance explicitly says around 30% in colder weather may be appropriate depending on the maximum tolerances of the building envelope. It is deliberately conditional. A Vancouver home at +5°C, a Winnipeg home during a -30°C cold snap, an older double-glazed window and a modern high-performance triple-glazed window do not have the same surface temperatures.

NRCan’s winter window-humidity table

NRCan publishes a useful illustration of that relationship. Its current table gives the maximum indoor RH at 21°C before condensation is expected on the listed window types.

Source: Natural Resources Canada, Keeping The Heat In - Section 9.

The most useful sentence on the NRCan page comes immediately after the table: occasional condensation is not necessarily a problem, while excessive condensation or frosting is an indication to reduce moisture production or increase ventilation.

That is why a hygrometer number and the physical pattern belong together.

Is 40% humidity good in winter?

Often, yes - 40% is inside Health Canada’s general range.

But if it is very cold outside and many room-side windows are wet or frosted, 40% may be more moisture than those surfaces can tolerate at that moment. Do not keep a whole-house humidifier pinned to 40% just because somebody else’s humidistat chart said so.

Should I set my furnace humidifier by outdoor temperature?

Treat generic temperature-to-dial charts as clues, not universal rules.

NRCan demonstrates that outdoor temperature changes condensation risk, but it also demonstrates something equally important: window performance changes the limit dramatically. The useful control loop is your actual RH plus your actual house response.

If widespread cold-weather condensation appears while the humidifier is running, reduce or pause added humidification and reassess. If condensation persists despite reasonable RH, investigate ventilation, local surface temperature and window performance rather than forcing the rest of the house drier without a diagnosis.

What should indoor humidity be in summer?

Health Canada recommends keeping indoor humidity below 50% in summer. Its broader mould guidance still uses the 30% to 50% band for indoor spaces.

Summer has the opposite problem from a deep Canadian winter: outdoor air can carry a lot of moisture. Health Canada’s ventilation guidance notes that increasing ventilation in a non-air-conditioned house during humid summer conditions can actually increase indoor humidity, while air conditioning and dehumidification can lower it.

That means “open the windows to dry the house” is not universally useful advice.

If the basement is cool and damp while the main floor feels fine, measure both areas before deciding the entire home needs the same treatment. Below-grade rooms often behave differently enough that the basement dehumidifier guide and sizing planner is the better decision system.

How to measure humidity in your house

You do not need a laboratory instrument to make the first household decision. A basic home hygrometer that reports relative humidity is enough to establish whether the reading is broadly low, within the general range or high.

An older but still practical CMHC consumer guide, Measuring Humidity in Your Home, makes three useful points:

• one hygrometer per house is usually sufficient for ordinary monitoring;
• put it where the humidity symptoms are most obvious, where you are most concerned, or where the household spends significant time;
• do not place it beside a radiator, heat register, chimney or another direct heat source.

CMHC also notes that a moved hygrometer can take up to two hours to settle at a new location. That matters when you carry one from a warm living room into a cool basement and immediately decide the reading must be wrong.

Do you need several hygrometers?

Not necessarily.

For ordinary monitoring, moving one instrument between the rooms you care about can be enough. Multiple sensors become useful when you are trying to compare spaces at the same time - for example, a basement against the main floor, or a bedroom with condensation against a room that stays dry.

The point is comparison, not collecting little LCD screens like Pokemon.

How can you check whether a hygrometer is reasonably accurate?

CMHC’s older guide includes a simple household calibration check:

1. Mix 125 mL (about 1/2 cup) of table salt with 50 mL (about 1/4 cup) of tap water in a cup.
2. Seal the cup and hygrometer together inside a roughly 5 L airtight bag or other well-sealed enclosure without letting the salty water touch the instrument.
3. Keep the setup away from drafts and direct sunlight at a stable room temperature.
4. After 8 to 12 hours, the hygrometer should read about 75% RH.
5. If the instrument cannot be adjusted, record the difference and remember the offset when interpreting later readings.

This is a basic accuracy check from an older CMHC publication, not a substitute for calibrated professional instrumentation. For the 30% versus 50% household decision, however, knowing that your cheap sensor is not wildly wrong can be quite useful.

My house humidity is above 50%. What should I check first?

Do not start with “which dehumidifier should I buy?” Start with where the moisture is coming from.

NRCan’s current moisture guidance tells homeowners to reduce water vapour at the source and specifically points to indoor clothes drying, clothes dryers that do not vent outdoors, humidifiers, basement water, standing water, household moisture-generating activities and kitchen/bathroom exhaust.

A useful first pass is:

1. Pause unnecessary added humidity. If a portable or whole-house humidifier is running while RH is already high, that is an obvious first variable.
2. Use exhaust where moisture is made. Kitchen and bathroom fans need to exhaust outdoors to remove that moisture from the house.
3. Confirm the dryer actually vents outdoors. A dryer dumping moisture indoors is not a dehumidifier-sizing problem.
4. Look downstairs. A damp basement, exposed wet materials, seepage or standing water can keep feeding indoor moisture.
5. Look for leaks. Plumbing, roof and foundation water should be fixed as water-source problems.
6. Check the ventilation system you actually have. In a tight home, an HRV or ERV that is off, dirty or being operated incorrectly can change moisture behaviour.
7. Use air conditioning or a dehumidifier when appropriate. They remove airborne moisture; they do not repair the source of liquid water.

If visible mould is already present, use the mould-in-the-home guide for the cleanup and escalation decision. Health Canada emphasizes that mould will return unless the underlying moisture cause is addressed.

My house humidity is below 30%. What should I check first?

A reading below 30% is below Health Canada’s general range, but the first move is still confirm, then diagnose.

1. Confirm the hygrometer reading

Let it stabilize. Move it to another representative room. If readings are unexpectedly extreme, check its accuracy before changing whole-house equipment.

2. Consider the outdoor conditions

Very cold outside air contains little moisture. When that air enters the house and is heated, its relative humidity becomes very low unless indoor activities or humidification add moisture back.

That is why a house can feel dramatically drier during a cold snap without the furnace somehow “burning up” water vapour.

3. Check ventilation and actual drafts

Health Canada’s residential ventilation factsheet lists very dry air in winter as one possible sign that a home’s ventilation rate is too high. Air leakage can also introduce more cold, dry outdoor air.

That does not mean every 25% reading proves the HRV is over-ventilating or the house is leaky. It means those are reasonable things to investigate.

If you can feel moving air at doors or windows, use the weather-stripping and draft guide to distinguish real air leakage from the normal cold-air movement that can happen near glazing.

4. Add humidity cautiously if you need it

If you use a portable humidifier, Health Canada says to follow the manufacturer instructions, empty leftover water after use, and clean/disinfect the reservoir regularly. Its current cool-mist guidance also says tap water is generally acceptable when the unit is maintained, while distilled water can reduce mineral particles released by some cool-mist models.

Most importantly, keep measuring. If added humidity starts producing widespread window condensation or frost, the current moisture level is too high for those cold surfaces even if you would prefer a higher number.

Humidifier vs dehumidifier vs HRV/ERV

These devices solve different problems.

Health Canada’s detailed Ventilation and the indoor environment explains the important HRV/ERV distinction: an HRV can dry a humid house in winter by diluting indoor moisture with dry outdoor air, but can also over-dry a house that is already dry. An ERV transfers some moisture as well as heat, so it tends not to dry the home as aggressively in winter.

If you do not understand the controls, balance or maintenance state of an installed ventilation system, follow the equipment manual or have a qualified HVAC/ventilation professional assess it rather than randomly changing dampers and fan speeds.

Why can windows condense at a “normal” humidity level?

Because room RH is not the same thing as surface RH.

A room might read 38% RH while one window edge, exterior corner or other thermal bridge is much colder than the air around your hygrometer. The thin layer of air next to that surface cools; its relative humidity rises; and if the surface reaches the dew point, condensation can form.

That is why lowering the whole house from 38% to 25% is not automatically the right response to one wet window.

Instead, ask:

• Is the moisture on the room side, outside, or between panes?
• Is it one window or many?
• Does it happen only during deep cold?
• Are heavy blinds or furniture restricting warm room airflow around the glass?
• Is the water actually tied to rain or snowmelt?

Those questions belong in the window-condensation checker, which is intentionally more specific than this whole-house humidity guide.

Humidity and mould: why there is no magic “mould starts at X%” number

Health Canada recommends keeping RH between 30% and 50% as part of controlling moisture and mould, but it does not turn 50% into a magic force field.

Mould growth depends on whether materials remain damp enough to support growth. A cold surface can have a much wetter local microclimate than the centre of the room. A leak can also wet drywall, wood or insulation even when the central hygrometer looks completely ordinary.

So use RH as one useful measurement, not as proof that a visible or musty area is safe.

If mould is visible, keeps returning, may be hidden, or follows flooding/leaking, switch to the ReadyHome mould guide. If the moisture appears with rain or snowmelt in the basement, use the basement waterproofing guide rather than asking a dehumidifier to fix exterior drainage.

A seasonal humidity routine that does not require obsession

You do not need to stare at RH every hour.

Fall / start of heating season

• Put the hygrometer somewhere representative and confirm it gives a believable reading.
• If you use a whole-house humidifier, inspect/maintain it according to the manufacturer before relying on it.
• Confirm bathroom and kitchen exhaust work and actually vent outdoors.
• Notice whether condensation begins as outdoor temperatures fall.

During a cold snap

• Check the RH and the windows together.
• If widespread room-side condensation/frost appears, reduce avoidable moisture and added humidification.
• Keep vulnerable sills/finishes dry while you correct the underlying balance.
• Treat one isolated wet window as a clue requiring a local diagnosis, not automatic permission to dry the whole house severely.

Spring and summer

• Stop adding humidity when it is no longer needed.
• Keep indoor RH below Health Canada’s summer guidance.
• Measure damp basements separately from warmer upper floors.
• Use air conditioning/dehumidification where appropriate, but investigate liquid-water entry instead of masking it.

For the larger cold-weather checklist, fold this into How to winterize your home in Canada.

Frequently asked questions

What is the ideal humidity in a house in Canada?

Health Canada’s general indoor recommendation is 30% to 50% RH. “Ideal” is not one exact number because season, outdoor temperature, surface temperatures, window performance and moisture problems change what the house can tolerate.

What should humidity be in a house in winter?

Use 30% to 50% as the general range, but expect the practical upper limit to fall during colder weather. Health Canada’s professional guidance says around 30% in colder weather may be appropriate depending on the building envelope. Persistent window condensation or frost is a sign to reduce moisture or improve appropriate ventilation rather than forcing one fixed percentage all winter.

What should humidity be in a house in summer?

Health Canada advises keeping indoor RH below 50% in summer. If the house or basement stays above that level, investigate moisture sources and ventilation and use air conditioning or dehumidification when appropriate.

Is 60% humidity too high in a house?

It is above Health Canada’s general 30% to 50% recommended range. A persistent 60% reading is a reason to check moisture sources, basement conditions, ventilation and whether dehumidification is appropriate.

Is 20% humidity too low in a house?

It is below Health Canada’s general range. Confirm the reading first. During very cold weather some homes may develop condensation even at relatively low RH, so do not blindly humidify toward 50% without watching the windows and other cold surfaces.

What is the ideal bedroom humidity?

ReadyHome does not use a separate unsupported “sleep humidity” target. Start with the same 30% to 50% general home guidance, then investigate why a bedroom differs if it repeatedly reads much wetter/drier or has localized condensation.

What should basement humidity be?

Start with the same general 30% to 50% indoor guidance, but measure the basement itself because its temperature and moisture load can differ substantially from upstairs. If it is persistently damp or above the general range, use the basement dehumidifier guide to separate airborne humidity from actual water entry and choose equipment appropriately.

Where should I place a hygrometer?

CMHC’s consumer guidance says to place it where symptoms are most obvious, in the room you are concerned about, or where the household spends significant time, and to keep it away from direct heat. You can move one hygrometer around the house; give it time to stabilize in each new location.

What should I set my humidifier to in winter?

There is no universal dial setting for every Canadian home. Measure indoor RH, use Health Canada’s general range as context, and reduce added humidity if widespread condensation or frost appears during colder weather. The correct operating control also depends on the humidifier and ventilation equipment you actually own.

How do I lower humidity in my house?

Start by reducing moisture at the source: use working kitchen/bathroom exhaust, vent the dryer outdoors, reduce unnecessary humidification, correct damp/leak sources and make sure the home’s ventilation system operates properly. Air conditioning or a dehumidifier can remove airborne moisture when needed, but neither fixes a leak.

Methodology

How this page was built: ReadyHome uses Health Canada’s 30% to 50% general home range as the baseline, then preserves the colder-weather building-envelope caveat from current federal professional guidance instead of inventing one national humidistat setting. NRCan’s current Table 9-1 is presented specifically as a window-condensation reference at 21°C, not a health target or code requirement. The hygrometer placement and salt-calibration procedure come from an older CMHC consumer publication and are labelled accordingly. Ventilation guidance comes from Health Canada’s residential ventilation publication. The checker uses deterministic routing from those ranges and observable moisture patterns; it does not calculate a fake risk score or infer window-surface temperature.