Humidifying ones’ home in the winter should be such an easy task, yet it is quite difficult to maintain a comfort level due to the constantly changing conditions in the home. Humidity conditions in the home should be in the range of 40 to 50% for optimum comfort. You can actually feel comfortable at a lower temperature if the humidity level is correct. To give the 40 to 50% Humidity level a point of reference, the Sahara desert averages about 20% humidity. I have deliberately left out a word at this point that pertains to humidity and that is the word “relative”. Relative Humidity or “RH” in future references is simply described as the amount of moisture that a volume of air can hold in vapor form at a certain temperature. Warm air can hold more moisture than cold air. Air that cannot hold one more drop of moisture is called “Saturated”. If more moisture is added to a saturated condition or if the temperature of saturated air drops, the moisture will condense and effectively fall out of the air. I have just explained why rain occurs, why the mirror in your bathroom fogs up during a shower and why moisture forms on the outside of your pop or beer bottle on a hot summer day. This same principle is how air conditioning works.
It is necessary to add humidity to your home during the spring, fall and winter months. If humidity is not added you will have dry scratchy throats, frizzy hair and likely get static electric shocks every time you shuffle across the carpet and touch someone or a door handle. Dry air can also cause your nasal mucus glands to kick into high gear and give you nasal drip. Too much humidity in a home creates a worse problem than too little. Mold can destroy a home and create health problems for the occupants and is a result of excess humidity. There are many things in your home that can reduce or lower your humidity, resulting in the need to add moisture. Appliances such as exhaust fans, clothes dryers, water heaters, fire places and some furnaces expel moist heated air to the outdoors forcing colder, dryer air to enter the home. This brings us back to the term relative humidity. If the outside air is saturated at 34 degrees F. or 2 degrees C., when that air enters the home and is heated the RH will drop to possibly 20% causing your humidifier to work overtime. Things that add humidity to your home are showers and baths, cooking, plant watering, fountains and aquariums. There are many types of humidifiers available for the residential market. Water left in a bathtub overnight will even add humidity to the home. There are portable humidifiers that can be moved from room to room, evaporative humidifiers that can be added to your furnace and even steam humidifiers that can be coupled with your furnace or inject steam direct into the air. The old style of humidifier that used a rotating sponge pad in a tray of water is quickly becoming a dinosaur because of the maintenance and stagnant water issues. Flow through humidifiers are the popular trend, but can use or waste a ton of water. Steam humidifiers are great at making steam and accurate humidity conditions, but they eat hydro for breakfast and are costly to maintain.
One of the biggest problems to controlling the level of humidity in your home is the use of programmable set back thermostats. Lowering the temperature while you sleep will produce a rise in the RH and you will sleep comfortably. Some humidity may be lost over night due to condensation on windows, but the problem is when the furnace comes out of setback in the morning before you rise and the temperature increase results in a rapid decrease in the RH. The humidifier cannot raise the humidity fast enough for you to avoid the discomfort until you take your morning shower. I have had customers call me saying they get nose bleeds due to the dryness. The solution is to NOT setback your heating temperature at night. This will maintain the RH and temperature at a constant. If there is a true problem with residential humidification it is the fact that the humidifier cannot keep pace with the heating system or rapid changes in the house temperature.
All residential humidifiers are controlled by a humidistat that works in similar ways to a thermostat. There will be a water line and automatic water feed device as well a drain on all permanent humidifiers. The switch action of the humidistat is operated by the shrinking or expansion of a strip of cellophane or horse hair. Steam humidifiers can also use this type of humidistathowever, the deluxe models would sense humidity in the air electronically. The location of the humidistat is best located sensing the air in the return air duct closest to the furnace where the condition is the true average for the house. Locating a humidistat next to the thermostat is acceptable, but can be affected by conditions in that local vicinity. The fan in your furnace must be on for the humidity to circulate through the system, yet during the spring and fall when you need the humidity the most, your furnace is not operating for as long a cycle as it does during the cold of winter. The solution to this problem is to switch the fan “Auto / On” button of your thermostat to the “ON” position for constant fan. This allows your humidifier to operate and you are also filtering the air with the fan operating.
You can check out the complete line of evaporative humidifiers by a Google search of “April-aire humidifiers” or steam humidifiers by Nortec or General Aire.