Ideal Indoor Humidity Levels & How to Control Them at Home

Ideal Indoor Humidity Levels & How to Control Them at Home

(Image credit: Brittany Purlee)

We all know that keeping humidity in your home during the winter is important for your skin, throat and overall health, but did you also know that it's vital to the health of your home? If humidity levels dip too low your furniture and house will deteriorate and certain germs will thrive. Let's talk about what humidity levels you should keep in your home year round, and different techniques to do so.

Ideal in-home humidity levels should hover around 45%. Anything under 30% is too dry, over 50% is too high.

If Humidity Levels Are Too Low

During the winter humidity levels drop because cold air holds less moisture than warm air. Homes that utilize forced air heating have an exacerbated problem because furnaces use combustion to create hot air, thus burning out most of the water vapor that existed in the first place. To make matters worse, when humidity levels dip the ambient air feels cooler than more humid environments, and we turn up the heat to compensate.

Low humidity causes static electricity, dry skin and hair, increased susceptibility to colds and respiratory illness, and can allow viruses and germs to thrive. Wood floors, furniture and millwork will split and crack, paint will chip, and electronics can be damaged because of low humidity levels.

Adding a humidifier to your home will remedy these problems; there are three standard types from which to choose:

Adding moisture to the air is as simple as placing a vessel of water on top of, or next to, a radiator (or other air heating system). Leaving wet towels and clothes out to dry are other ways to introduce moisture into the air. This is a very low-tech and low power method, however the strength and humidity controls are limited, and available moisture is dependent on the size of the vessel used, and must be frequently refilled.

The most common type of humidifier is a portable one. There are two types: cool mist and warm mist, both of which use a a reservoir to hold water. The cool mist uses a wick to absorb the water and a fan blows air through a moistened filter as the air passes through the filter, it evaporates some of the water into the room. Warm mist humidifiers use a heating element that heats the water before dispersing it into the air. The pros of portable systems are that they are easy to use, a variety of styles and prices are available, and they can be moved as needed. However, similar to the evaporative method above, control and measure of relative humidity is limited, and the reservoir must be refilled about every 24 hours.

Whole House
This is the best and most controllable humidity system. A whole house humidifier is added to a furnace and vapor is distributed directly into the heated air and circulated throughout the house via the furnace duct system. The system is the most expensive, can be installed by owner or a professional, and requires a cold water connection and room for the humidifier unit. Humidity levels are controlled via a humidistat and the method has the greatest humidification capacity and is most consistent.

If Humidity Levels Are Too High

It is possible for homes to have too much humidity, which will create its own set of problems, particularly the issue of condensation. This does not typically occur in older homes, but new, tightly constructed buildings will retain more heat and moisture, which is when mechanical ventilation is important. During the winter you will first notice this at windows: when warm, moist air comes in contact with a cold window, air temperature drops and it can no longer hold the water vapor and condensation results. If a home does not have the proper mechanical and natural ventilation, excess water vapor can travel through walls and ceilings, causing wet insulation, peeling paint, and mold on walls and rot in woodwork. Try these steps to lower humidity in your home:

  • Turn down or off humidifier, and use a dehumidifier when necessary – particularly in basements and during the summer.
  • Use exhaust fans while cooking and bathing or open a window to exchange fresh, drier air.
  • Reduce the amount of water introduced into the home by cooking with covered pots; taking cooler, shorter showers; venting clothes dryers directly to the outside; and reduce the number of plants in the home.
  • In tightly constructed homes, use an energy recovery ventilator.

How to Gauge Indoor Humidity Levels:

  • Fogging and condensation accumulating on windows, moisture and mold occurring on walls and ceilings is an indication of too much humidity.
  • Increased instances of static electricity, dried and cracking millwork and paint indicate low humidity levels.
  • Use a digital or analog hygrometer to measure humidity levels.
  • If you use a whole house humidification system, use a humidistat to control and monitor humidity levels.
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