Home Humidity Needs Balance

Overdoing it - Too Much Humidity Creates Problems

I have a humidifier attached to my forced air heating system. It is a neat device. Many people have them. Every time the furnace turns on, a little electronic switch opens a small water valve. Water flows over a pad through which air flows. The water evaporates from this pad into the air. BINGO! The humidity starts to rise inside your home.

Well, sometimes - and this has happened to me - you can get too much humidity. I have gone to bed with everything just fine. The furnace was humming and the humidifier working just fine. I wake up and it looks like someone turned on a lawn sprinkler inside my house near every window. Water is running down the windows and pooling on the floor! I usually run around cleaning up saying, "We've had a major malfunction. All engineering personnel report to the quarter deck immediately!"

The cause of the problem is easy to identify. Two things possibly occurred at the same time: the inside relative humidity was climbing and/or the outdoor temperature level dropped. Usually it is the outside temperature drop that causes the problem. The inside temperature of the window glass drops as the outside temperature drops. The water vapor in the air begins to condense as the temperature of the glass drops.

Hidden Problems

If you have had water condense on your windows like me, you may have had more serious problems. There is a good chance that water condensed on hidden, cold wall or attic spaces. Remember earlier we talked about air leaking into and out of your house? Well, those places where it is leaking out may be saturated with water. Recently I had a caller to my radio show tell me about basement fiberglass insulation that was saturated with water. The insulation was up against the band board (rim joist) just above the foundation. This framing lumber has a direct connection to the cold siding outside.

It transmits this cold into the basement. Just like a cold can of soda or beer begins to sweat in the summer humidity, so will this rim joist inside. But, what happens if this is going on inside the walls of your house where you can't see? How about your attic? These are all possibilities. Wood rot, mildew, etc. can become a real threat.

Maintaining a Balance

If you have a humidifier, or plan to purchase one, you need to pay attention to outdoor weather. If the temperature is forecast to drop over a period of hours, you may wish to turn down or limit the amount of humidity you are introducing into your air.

Many manufacturers recommend that you adjust your humidifier to a setting just before any fog would appear at the edges of a window. Remember, this fog will appear at different outdoor temperatures and different indoor relative humidities. It is not easy to do! There is no one setting that will work for all outdoor temperatures. Plus, if you have a programmable indoor furnace thermostat the problem gets worse! At night, you probably have the thermostat set itself back 5 to 7 degrees. Well guess what? This will cause the indoor relative humidity to rise in and of itself with no adjustment at all to your humidifier. Maintaining proper indoor humidity is not easy.

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