It’s winter, and for many people, that means dry skin, cracked lips and nosebleeds, so I’m often asked about whole-house humidifiers – humidification systems that connect to your central heating system to distribute moisture throughout the house.

As noted in another post, I’m not a big fan of these units. Any time you concentrate humidity, you run the risk of growing mold. A little leak in your duct system and you could be squirting moisture into walls, ceiling cavities or other areas where you might not know there’s a problem until the entire thing rots out.

It is vastly preferable to use standalone units that use cold water, a small fan and a pad to soak the water. These units are very energy efficient. But beware, there are energy hogs among the small units too. some of them have electric heating elements to evaporate the water and use ten times the electricity as the simpler models! 

In spite of my personal aversion to these units, I recently worked with a friend to track down the source of her high electric bills. She’s an engineer too, so she was reading manuals and trying to uncover the problem. 

As it turned out, she told me “Ted – I have a whole house humidifier, could that be an issue? It runs on hot water.” I’ve heard of this before. Units that squirt hot water into the air stream of the heating system. The trouble is, her unit worked very inefficiently, running the hot water the entire time the heating system is on!

Let’s look at this. This system was basically leaving the faucet on for 8-16 hours per day, using 50-100 gallons of hot water just to put a few gallons of moisture into the air. What a horrible waste!

When you run the numbers, you find that, at the low end, this was costing her $30/month to run. However, with high electric rates in the northeast U.S. and cold winter days, this number is about $100/month! 

Fortunately, there are other ways to solve the problem. If you must have a whole-house humidifier, look for one that doesn’t use hot water and doesn’t run the water the entire time your heating system is on. You’ll have to do your homework, and maybe argue with your heating contractor who will just want to install whatever unit they have sitting on their truck. But it’s your utility bill, so don’t settle.

Guidelines for choosing a whole house humidifier:

• It should run on cold water, not hot water
• It should only run if the humidity is below the set point
• It should not run water continuously when the heating system operates

In addition, whole house humidifiers can be breeding grounds for mold, depending upon the design, so make sure you service it regularly. That means draining the unit and opening it up to clean it out as per the manufacturer’s instructions. Off-season (typically Spring, Summer and Fall), they should be disabled, otherwise they work against your air-conditioning system causing it to work extra hard.

So if you have high utility bills this winter, check to see if you’ve got a whole house humidifier. It could be pouring your utility $$$ down the drain!

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