Ask the Builder
Indoor Humidity, How Much?
By Tim Carter
©1993-2009 Tim Carter
Summary: Cool air intake can lower humidity causing static electricity. Water vapor exhausts causing condensation. Check your humidifier and seal areas cold air enters.
DEAR TIM: My house seems to require more humidity in the winter than my neighbor's house. Both houses are the same age, size, style, and use identical heating and humidification equipment. I constantly get zotted by static electricity at my house but not at my neighbor's house. Our humidistats and thermostats are set identically. Both have been calibrated and are functioning properly, but my heating bills are higher. The weatherperson on TV reports relative humidity readings in excess of 70 percent daily. What is going on? I. S.
DEAR I. S.: So, those finger tips are a little tender? Well, I may be able to help you and save you some money at the same time. There are several things that may be happening in your situation. More than one thing could be wrong. Let's start with the easy things.
Let's check your humidifier first. Make sure that the water supply to the humidifier is turned on and that water actually flows into your humidifier. Some humidifiers have a small plastic flow restrictor at the end of the water tube as it enters the humidifier. This restrictor has a very tiny hole through which the water flows. If obstructed, this could be the source of your problem. I have had trouble in the past with this restrictor on my own humidifier.
The water transfer pads or media inside the humidifier may be clogged with mineral deposits. If this is the case, cleaning or replacing them should solve the problem. Often these pads can be reused by allowing them to soak in warm vinegar. The acidic vinegar dissolves the mineral deposits. You may need to let it soak overnight and repeat the process to remove heavy mineral buildup.
If your humidifier is working properly and you still have lower indoor relative humidity than your neighbor, it is a sign of a more serious problem. Your higher heating bills may be the clue. I feel that your humid air is leaking out of your house and being replaced by drier, outside air.
Don't be fooled by the weather reports. As the temperature of air drops, it can hold much less moisture. The relative humidity of cold outside air may well be 70 - 80 percent. Bring this air inside, heat it to 72 degrees, and the relative humidity of that same air drops to 2 percent!
Houses often have hidden air leaks. Seal any and all areas where you feel cold air entering your house. If you feel cold air entering, it is a sure sign that humid, warm air is escaping. If you can inspect your attic, look for places where pipes and wires penetrate the attic from below. Quite possibly these penetrations are not sealed. Look for these same penetrations in your basement ceiling. Often, electricians and plumbers create open chimneys within exterior and interior walls when they install their wires and pipes.
Once you locate the leaks, adjust your humidifier to a minimal setting. Most normal household activities (bathing, breathing, cooking, etc.) produce adequate indoor humidity. Don't overdo it!
