Is My Indoor Relative Humidity OK?

Question from Jim Brockway

"At 68 degrees in home, my humidity is 25.  Is that OK?"

Excellent question, Jim.  The answer is…it depends.  The critical temperature is not the temperature inside your home, but the temperature outside your home.  Have I confused you yet?  Let me explain.

The proper level of indoor relative humidity (RH) is a moving target based mainly on the outdoor temperature.  The lower the outdoor temperature, the lower your indoor RH% should be.  This is to prevent condensation from forming on your windows and in your walls.  An example would be a glass of your favorite beverage with and without ice in it.  Without ice, the beverage is warmer and the outside of your glass stays dry.  When you add ice to chill it, the outside surface of the glass is cold and begins to sweat.  Unless you have a coaster, you get water all over the surface it’s sitting on, which can ruin it. 

Proper indoor RH is no different.  An Aprilaire whole-house humidifier with premium digital control utilizes an outdoor temperature sensor to continually adjust your indoor RH, providing maximum comfort and protection 24/7. 

Now, to answer your question, 25% indoor RH is about perfect when your outdoor temperature is at 0 degrees Fahrenheit.  That’s pretty cold.  At 20 degrees Fahrenheit, you should be around 35%, and at 40 degrees or higher, you should be at 45% indoor RH.  I’m going to guess that your outdoor temperature is not zero and that you are in dire need of humidification.  Please contact your local Aprilaire dealer and schedule the installation of your Aprilaire humidifier with premium digital control today.

Thanks for the question, Jim. 

One thought on “Is My Indoor Relative Humidity OK?

  1. Perry

    I have a question. I have an old Aprilaire humidifier attached to my home’s furnace. There is a dial on it that says either dry (20 or lower) or moist, 40 or higher. So what does this mean? the label says relative humidity, but does that mean the relative humidity outside or inside my house? I live in chicago, and its 0 degrees today and my basement windows have so much moisture on them, that they have iced over! I had the RH dial set to DRY, or 25-30. Help!


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