Humidity at Home: What You Need to Know this Winter

Understanding Relative Humidity in the Home

Relative humidity comfort ranges on a scale of 0 to 100.

Humidity simply refers to the amount of moisture in the air. Breaking down the math, relative humidity is the percentage of water vapor that’s in the air at a certain temperature. When the relative humidity is at 30 percent, for example, the air is holding 30 percent of the moisture it’s capable of containing.

During colder months, the air’s ability to hold water decreases, and during warmer months, it increases. The ideal relative humidity level for the inside of your home is between 30 and 50 percent. This is important because the level of humidity in your home can impact your overall health and comfort and potentially affect the cost of heating or cooling your home.

Infographic showing the risks of humidity levels that are too high and risks of humidity levels that are too low.

If humidity levels are too high you run the risk of:

  • Growing mold and bacteria
  • Stuffy conditions
  • Overall discomfort

If humidity levels are too low you run the risk of:

  • Catching a cold or infection
  • Dry and itchy skin
  • Damaging the wood, paint or siding of your house

Oh, the weather outside is frightful…

Let’s say it’s a cold day in December. The temperature outside is 10° F with 70 percent humidity. Meanwhile, indoors, your thermostat is set to 72° F. When the cold air creeps into your home, your furnace heats it to 72° F, and the air expands. While the moisture in the air remains the same, the relative humidity is significantly reduced. This means that the cold air from outside with 70 percent humidity has an indoor relative humidity of only 6 percent.

The dry air inside your home will steal moisture from wherever it can find it, including your body. As moisture evaporates off your skin, you feel cooler. When you feel cooler, you tend to turn up your thermostat, which can become an expensive habit given the high cost of heating.

Protecting yourself and your wallet

To combat the negative effects of dry air, it’s important to keep your home’s indoor relative humidity level somewhere between 30 and 50 percent. This minimizes the air’s need to replenish moisture and little or no evaporation from your body takes place. As a result, you can actually turn down your thermostat about three degrees and maintain comfort and warmth while saving on energy costs.

There are many different ways to humidify the air in your home. You can use a single room humidifier or install a home humidifier connected directly to your HVAC system. These humidifiers work automatically to ensure the air in your home is at an ideal relative humidity level. It is also recommended to use a more accurate digital thermostat with humidity control to automate the process and keep your system at peak efficiency.

Ask your contractor about humidity in your region and the best way to protect your health and comfort while saving money.


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33 thoughts on “Humidity at Home: What You Need to Know this Winter

  1. You are using a less accurate way to measure “air comfort.” Relative Humidity is not the Measurement to use, when evaluating human comfort levels.

    Dew Point is the point that water vapor is extracted from the air and turns to liquid form. When the Dew Point is High, a human body’s ability to cool is limited because is doesn’t evaporate as quickly, (and so efficiently.)

    The Dew Point is the value we should look at if we want to know how comfortable it is. It is also the measurement to use when trying to determine the Potential Heat Risk to Humans.

    • I’m about 70 years old and have always used an RH gauge to perfect my comfort at 38% to 42%. What kind of dew point meter do you use and how expensive is it? There would never be a dew point inside your home to be concerned with anyway unless you like your RH @ nearly 110%. Dah!

  2. I am in a 7th floor one-bedroom condo (top floor) in Boston, and when it gets cold in winter, the relative humidity gets very low ( shows as constant 15%RH). I use a 1.5 gallon humidifier in my bedroom, and although 1-2 gallons of water is used up per day, the RH stays as 15% RH. I know the hygrometer works because today it is 55 and raining and it is reading 48%RH. Should I give up on using a humdifier?

  3. In this case your window seals are no longer functioning properly so it kind of goes like this when it’s cold outside and it’s warm inside and you’ve brought the humidity levels down lower than 50%. It’s creating such an extreme environmental change from the inside to the outside that the inner lining of the window is sweating just like a cold bottle is put on a counter and slowly cools it starts to sweat same idea I would recommend that it’s time for some new windows

  4. the house is either under insulated or over insulated both of these could cause excess levels of humidity and moisture and also in some cases can cause excess dryness and lack of moisture in a home

  5. I have high humidity problem in my house. I was told to run the main exhaust fan to drop the RH in house.
    The RH outside is 70% at -10 degrees while inside house is 50% RH at 21dedrees indoor temperature. I have have been running the exhaust fan for days but wasn’t able to reach my target of 35% RH. Any suggestions? Also still not sure about the connection between outdoor and indoor RH.

    • You can purchase dehumidification systems in India from your local HVAC distributor. They would need to evaluate the building to determine if you require a stand alone or how building system.

  6. I was in Ottawa relative humidity 23 in house no dry skin. In Regina relative humidity 30 in house dry skin. Have HVR system and humidifier in Regina. Out side temperature -5c both places. Why would i have dry skin in Regina

  7. It has been a particularly humid summer (in the high 70s to mid 80s °F with over 80% humidity), and everything in the inside of my house feels damp. My clothes, my carpet, even my bedding. We bought a fairly large dehumidifier, but we are emptying out at least two gallons of water in the thing per DAY. I have never lived in a house that was this humid, and I am wondering if I need to have my landlord call someone to see if there is another problem. He insists that it’s just the outside humidity that is making it so moist in here, but I wanted an expert opinion. I don’t need to be breathing mold! Thanks in advance for your advice 🙂

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