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Heat from your furnace warms the air in your house, and dries it out, too. Forced hot-air systems in particular can lower indoor humidity to the point at which people feel uncomfortable. To add moisture to dry winter air and create an indoor environment that's comfortable for you and good for your house as well, you can use a variety of portable or central humidifier systems. The most economical systems connect to the furnace. These have a moisture control, called a humidistat, and feed moisture directly into the warm airflow.
Portable, or console, humidifiers are concealed in small cabinets. They are helpful if one room is particularly dry or if you have a heating system without an air-distribution system, such as electric baseboards, that isn't suited to a central humidifier system. The drawback is that you have to add water to console storage tanks periodically. Also, they require maintenance much more often than central systems.
Central humidifiers are attached to the home heating system, normally at the plenum, where heated air is distributed to the ducts (see instructions below). The advantage is that the appliance is part of the house; you don't have to plug it in or add water. But an automatically replenished water supply can become a breeding ground for pollutants that are spread through the ducts and into living areas. Treating the water and doing seasonal maintenance can reduce this problem.
If you are shopping for a humidifier, bear in mind that two of the four basic types, just by their design, are more likely to disperse microorganisms. Ultrasonic humidifiers, which use high-frequency sound waves to generate a cool mist, and impeller humidifiers, which make a mist with a high-speed rotating disk, produce the greatest dispersions of microorganisms and minerals. Breathing misted air containing microscopic dust mites, mold, bacteria, and other pollutants can cause respiratory problems and allergic reactions. The other two types of humidifiers generally disperse fewer pollutants. Evaporative units pick up water from a holding tank with a belt, sponge pad, or wick that is exposed to the airflow from the furnace. Warm-mist or similar steam-vaporizer humidifiers can completely eliminate pollution problems. A heating element boils the standing water before it is dispersed as mist into the airflow, which distills the minerals and kills bacteria and mold.
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1.
Mark the Placement of the Humidifier
In a typical installation, you tape a paper template for the humidifier on the main return plenum above the furnace. Use a level to make sure the lines of the template are level. Also mark the position of the humidifier duct on the main supply plenum. Then, using metal shears, cut through the template and sheet metal along the lines on the template. To protect yourself, wear work gloves and safety goggles. (Fig. 1)
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2.
Install the Humidifier
Position the humidifer in the main return plenum, making sure it is level. It's important to level the humidifier for even water distribution; this unit has a small bubble level built into the water tray. Then fasten the humidifier in place, following the manufacturer's instructions. (Fig. 2)
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3.
Cut Hole for Duct
Using metal shears, cut through the main supply plenum to make a hole for the humidifier supply duct. This kit comes with a mounting collar. (Fig. 3)
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4.
Connect Duct
Using flexible duct or a length of standard metal duct and an elbow fitting, connect the humidifier to the supply plenum. (Fig. 4)
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5.
Install Solenoid Valve
A typical humidifier has a solenoid valve to control water flow. This small pipe runs from the valve to the distribution tray. (Fig. 5)
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6.
Provide Water Supply
To bring water from your supply piping to the unit, most humidifiers use either flexible copper pipe or hard plastic tubing. (Fig. 6)
Install a saddle valve (if permitted by code) on the supply pipe. Clamp it to the line, and turn the handle to pierce the pipe. (Fig. 7)
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7.
Provide for Recirculation or Overflow
Central-system humidifiers typically have a catch basin that recirculates water, or an overflow drainpipe like this one. (Fig. 8)
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8.
Install the Humidistat
Following the instructions that accompany the humidifier, install the humidistat on the plenum or near the existing thermostat (Fig. 9). A humidistat allows you to regulate the indoor humidity.
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