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The Proper Humidity Level in the Home and How to Control It

by Daniel Estevao on January 13, 2017

Proper Healthy Humidity Level in the HomeThis winter, we’ve been hearing one word a lot from our customers: humidity. Homeowners want to know how to keep their home comfortable, at the healthiest level of humidity, in order to prevent the build-up of mold and moisture problems on one end and static electricity, dryness, and damage on the other.

You may think the Pacific Northwest is always wet, with relatively high humidity levels. The important distinction, however, comes from the difference between relative humidity and dew point. Don’t be fooled by when you google your area’s humidity and it tells you 75%. A much more accurate measurement of atmospheric moisture comes from looking at the dew point and temperature.

Relative Humidity vs. Dew Point

These two often get confused, but there are clear differences between the two. Relative humidity is basically the amount of moisture in the air versus how much moisture it can hold, however, it gets complicated. Air can hold a lot more moisture when it is hot outside than when it is cold outside, for example.

The simpler and easier way to determine the humidity in the are is by referring to the dew point rather than relative humidity:

  • <55°F — Dry
  • 55-60°F — Comfortable
  • 60-64°F — Rather Humid
  • 65-69°F — Humid
  • 70-75°F — Very Humid
  • >75°F — Oppressive

Although the Puget Sound region gets a lot of precipitation, the winters can get pretty dry. Relative humidity will be high, but dew points can get very low.

In the winter, the air is cold. Cold air doesn’t hold much water vapor, meaning that the colder the air gets, the drier it gets. Cold air is dry air. That’s why you go through so much lotion and lip balm in winter.

Without proper insulation, this dry winter air comes into your home and mixes with your heated indoor air. If you have a vented furnace, then the air it consumes must be replenished with outdoor air, which is cold and dry. This makes your indoor air even drier! As a result of winter air and running your heating system, you’ll experience the low indoor humidity level homeowners are worried about.

There is a delicate balance at play here. Too much humidity and you’ll get moisture that will build up on your windows and unforeseen within your walls, and this moisture can eventually cause mold, rotting and poor health. Too little humidity and your home’s air will be so dry that you’ll be facing electrical shocks from a variety of surfaces and potentially even bloody noses!

What is the ideal humidity for my home?

Ideally, the relative humidity (RH) in your home should stay between 30%-50% to retain comfort and health. In the winter, condensation on the windows may occur if the RH is not below 40%. By maintaining this level of humidity in the winter you will create the most pleasant environment for your home.

The goal is to avoid both damaging dryness and excessive moisture. How can you do this?

How to Combat Dry, Winter Air

A whole-home or stand-alone humidifier is the first solution sought by homeowners to combat high or low humidity levels. Talk to Pacific Air Systems for more information on the best humidifiers for your home.

Some homes have windows that are less prone to condensation, and other homes are less insulated and more prone to dry air. You will need to adjust your humidifier accordingly so that you don’t over-humidify, causing its own set of moisture-related problems. If you have a whole-home humidifier, just set it and forget it.

Effects of low humidity:

  • Static electricity
  • Dry skin
  • Irritation of nasal passages
  • Throat irritation
  • Itchy eyes
  • Moisturizing expenses

How to Measure Indoor Humidity

Anytime that moisture is evident in the home—foggy windows, presence of mold—the humidity is too high! If you’re experiencing build-up of static electricity and respiratory irritation, the humidity is too low!

DIY test for humidity — get a glass and put 3 ice cubes in it, fill with water and stir; wait three minutes. Is there condensation on the outside of the glass? If not, your air is too dry. This isn’t an exact science, but it’s a visual affirmation that you need a humidifier.

You can even go the route of purchasing a hygrometer, aka relative humidity (RH) indicators, to measure the amount of condensation and evaporation in the home. Battery-operated, they give you the indoor RH, an indication of whether or not the level is “OK” or not, and the indoor temperature.

Humidity & Temperature

As a general rule, here’s how it should be: the lower the outdoor temperature, the lower the indoor humidity.

The Star Tribune breaks down how indoor humidity levels correspond to outdoor temperature:

  • If outside temperature is 20 to 40 degrees, humidity indoors should not be more than 40 percent.
  • If outside temperature is 10 to 20 degrees, humidity indoors should not be more than 35 percent.
  • If outside temperature is 0 to 10 degrees, humidity indoors should not be more than 30 percent.
  • If outside temperature is 10-below to 0, humidity indoors should not be more than 25 percent.
  • If outside temperature is 20-below to 10-below, humidity indoors should not be more than 20 percent.
  • If outdoor temperature is lower than 20-below, inside humidity should not be more than 15 percent.

For a happy and healthy winter, avoid low humidity in the home with a whole-home humidifier installation or a proper portable humidifier.

If you have any questions, don’t hesitate to contact one of our Comfort Advisors at 253.292.3995.

Additional Resources: 


Pacific Air Systems offers year-round HVAC and humidifier services.

Contact Pacific Air Systems Heating & Cooling at 253.292.3995 for 24/7 service (holidays included)!

Since 1984, we’ve been proudly serving our communities in Federal Way, Graham, Spanaway, University Place, Steilacoom, Sumner, Lakewood, Puyallup, Tacoma and Gig Harbor.

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