Condensation is one of the biggest problems in a modern, well insulated home.  Additionally, it is the one which is most misunderstood.  Left untreated, condensation can lead to mold growth which can be potentially harmful and lead to serious health issues and breathing difficulties which is why it is important to reduce humidity levels in a home.

When condensation appears on the interior of your windows, everyone assumes it must be the windows.  Your home is insulated to protect against extremes of outdoor temperatures. With this insulation, a vapor barrier is installed to prevent moisture from getting into wall, ceiling and floor cavities where it can cause damage. Since moisture cannot escape through the structure the excess must pass through the any opening built into your home.

In daily living you add moisture to the air by breathing, cooking, washing clothes, bathing and even by heating your home with gas. As a homeowner you must control condensation so that it doesn’t cause damage to the surfaces and the structure of your home.

Based on keeping an indoor temperature of 70 degrees, humidity will vary with the outdoor temperature.  Use the following maximum recommended humidity levels to keep condensation under control:

Outside Air Temperature                 Maximum Recommended Indoor Humidity Level

-20 F or Colder                                   Up to15% Maximum

-20 F to -10 F                                      Up to 20% Maximum

-10 F                                                    Up to 25% Maximum

0 F                                                      Up to 30% Maximum

10 F                                                     Up to 35% Maximum

20 F to 40 F                                       Up to 40% Maximum

Humidity levels above these are not recommended unless special provisions are taken during construction.

 Here are a few tips that can help you control humidity:

  • When cooking on the range, turn on the exhaust fan in the hood above it, which will carry moisture from cooking outdoors.
  • When taking a shower or bath, keep the bathroom door shut to confine the moisture in the bathroom alone. Turn on the bathroom vent fan or open the window slightly for 30 minutes to let excess moisture escape.
  • When doing laundry, avoid hanging wet clothes in your home. Use a dryer if you have one; it exhausts moisture directly into outside air.
  • Avoid storing firewood indoors.

The humidity level that should be maintained in your home varies with outside temperature.  The colder it is outside, the lower the humidity level must be inside your home.  Keep in mind not to take your humidity too extreme, or you’ll experience shrinking and drying of walls, wood floors and cabinetry.  All major manufactures of humidifiers list the recommended humidity settings based on outside temperatures. 

When in doubt, consult a Home Maintenance Expert to review your home to control Condensation before damage is done.