humidifier on furnace new constructionHumidifiers are very common in homes in the northern, colder climates. Here in Michigan, you would be hard pressed to find a house that doesn’t have a humidifier running during the heating season. The common line you’ll hear from everyone is that a typical gas furnace is a “dry heat” and that it drys the house out, therefore, you need a humidifier to put the humidity back in. The error in that thinking is that the furnace is NOT drying the house out. What’s drying the house out is all the air leaks that are letting the warm humid air leak out and get replaced by dry cold air from the outdoors. The cold air then causes the thermostat to tell the furnace to come on and heat the house back up.

The truth of the matter is that a high-performance home does not need a humidifier.

The humidifier is a band-aid that is covering up for the air leakage. The truth of the matter is that a high-performance home does not need a humidifier, and if your home does need one, you need to look further into WHY it needs a humidifier and fix THOSE problems. It may mean that a humidifier is your best option for problems that can’t be easily fixed, but you must realize that the problem is the air leakage, duct leakage, or another performance problem. If it’s a new home, and you expect it to be energy efficient, you might start asking questions of your builder.

In fact, if the house is air-tight and energy efficient, humidity is going to be a problem to get rid of, not something you want to add more of back into the house.  ENERGY STAR Certified homes, as well as most homes built to modern codes, are required to have spot ventilation in the kitchen and bathrooms that performs to certain airflow requirements to exhaust excess humidity. ENERGY STAR requires 50CFM in the bathroom and 100CFM in the kitchen, and that’s tested actual airflow, not just what the sticker on the fan says.  In addition, ENERGY STAR also requires automatic mechanical ventilation to bring new fresh air into the house.

So here’s your action plan:

  1. Get a blower door test to measure and find air leaks
  2. Seal the leakage (Hint: more than 50% of your leaks will be huge leaks, so start with the big holes first and deal with mini-leaks later; don’t underestimate the little ones though, they sure add up fast.)
  3. Make sure your ducts are not leaking air to the outside and seal any leaks you find
  4. Monitor your humidity with a hygrometer to measure the relative humidity in the house. 35% to 45% is the comfort zone. More than that and you’ll have condensation on the windows and a clammy feeling. Lower than that and you’ll have static electricity, itchy skin, and maybe nosebleeds.