What is a healthy indoor humidity range?
Relative humidity is the amount of moisture in the air compared with the most it could hold at that temperature. Most guidance for homes lands on roughly 30 to 50 percent as a comfortable, reasonable range. Below that, the air feels dry. Above it, the air feels heavy and moisture starts to collect where you do not want it.
Winter changes the target. Cold glass, cold wall corners and cold frames are the first places moist indoor air will condense. When the temperature outside drops hard, the same indoor humidity that felt fine in October can start fogging windows in January. That is why the advice is to run at the lower end of the range in very cold weather.
Why is winter air so dry in the first place?
Cold air holds very little moisture. When that outdoor air leaks in and gets heated to room temperature, its relative humidity drops sharply. The Salt Lake Valley is already a dry climate, and a forced air furnace running through a long cold season pulls the indoor number down even more.
Tighter houses hold on to what moisture they have better, and leakier houses exchange more air with the dry outdoors. Either way, a heated home in a dry cold climate commonly ends up on the dry side without any help.
What are the signs the air is too dry?
Your body and your house both tell you. People notice it first.
- Dry or itchy skin, chapped lips and a scratchy throat.
- Nosebleeds or a dry, irritated nose, especially at night.
- More static shocks when you touch doorknobs or walk across carpet.
- Wood floors that show gaps between boards, or cracks in wood furniture and trim.
- Houseplants that dry out fast and droop.
- Sleep that feels worse than it should, with a dry mouth on waking.
What are the signs the air is too humid?
In winter, too much moisture is less common than too little, but it happens, especially in tight homes with lots of cooking, showers and drying laundry indoors. The giveaway is condensation.
- Fogged windows, or water running down the glass and pooling on the sill.
- Frost forming on the inside of windows.
- Musty smells, or dark spots in corners, around windows and in closets.
- Peeling paint or a damp feel to walls on the north side of the house.
- A stuffy, heavy feel even though the temperature is comfortable.
How do you measure humidity at home?
A hygrometer is a small, inexpensive meter that shows the relative humidity in the room. Many also display temperature. Place one in the main living area and another in the bedroom, away from the kitchen, bathroom, heating vents and direct sunlight, which can skew the reading.
Check it at different times of day. Humidity moves as you cook, shower and sleep, and as the weather outside changes. Over a week or two you will see what your house does on its own. Handheld meters differ in accuracy, so compare two if the reading seems off, and treat the number as a guide instead of a precise measurement.
What are your options for adding humidity?
If the readings stay low and you are living with the symptoms, there are a few ways to add moisture.
- Portable humidifiers cover one room. They need frequent cleaning and refilling, and they are only as good as the attention you give them.
- Whole-home humidifiers connect to the heating system and water supply, and add moisture to the air as it circulates through the house, controlled by a humidistat.
- Steam humidifiers produce moisture by heating water and suit larger homes or higher demand.
- Simple habits, like not venting every shower fan to the point of dryness, make a small difference but rarely solve a truly dry house.
Is a whole-home humidifier worth considering?
If you are refilling portable units every day and still fighting dry air, a system that is built into the furnace and runs on its own is worth a look. Rocket installs whole-home and steam humidifiers, and a technician can tell you which type suits the house and the heating system you have.
Whatever you choose, set it by the outdoor temperature. Running a humidifier at a high setting during a deep freeze is how people end up with wet windows and damp framing. Keep an eye on the hygrometer and lower the setting when it gets very cold.
Frequently asked questions
Is 30 percent humidity too low in winter?
It is at the low end of the commonly cited comfortable range, and often fine in very cold weather. If you feel dry skin or get static shocks, a modest increase may help, but watch the windows.
Why do my windows fog up in winter?
Warm, moist indoor air is condensing on cold glass. It usually means indoor humidity is high for the outdoor temperature. Lowering the humidifier setting or improving ventilation often clears it.
Can a furnace make the air drier?
A furnace does not remove moisture, but heating cold outdoor air lowers its relative humidity. Long cold seasons with a lot of heating leave many homes dry.
Where should I put a hygrometer?
Put it in a main living space or bedroom, away from vents, sunlight, the kitchen and the bathroom. Check it at different times of day to see the pattern.
Do I need a whole-home humidifier?
Only if the air stays dry and portable options are not keeping up. Measure first. If readings sit in the comfortable range, you may not need one.
