Ventilation is key when fighting condensation around your home


By CCHRC Staff

The “Ask a Builder” series is dedicated to answering some of the many questions Fairbanks residents have about building, energy and the many other parts of home life.

Q: How can I keep condensation off my windows in the winter?

Condensation is a product of the relationship between humidity and temperature.

The warmer the indoor air is, the more water vapor it can hold. When the air moves next to a window it can no longer hold the same amount of water vapor because the temperature is colder close to the window. This is when you start seeing condensation forming. As an example, if your indoor temperature is 70 degrees and outdoor temperature is 0, then moisture will begin to condense on a single-pane window when there is roughly 15 percent relative humidity in the house. A double-pane will be subject to condensation at around 25 percent to 40 percent humidity, and a triple-pane will fall into a range of around 30 percent to 50 percent. These number ranges are based on average window insulation values.

A really good triple-pane window may be able to withstand significantly higher humidity levels before condensation occurs. The target humidity levels for occupant comfort in a home range from about 30 percent to 50 percent, however the lower end of this spectrum is considered safer in cold climates such as ours, due to concerns with condensation within walls and ceilings. When the humidity is really low, some people become prone to respiratory infections. Of course high humidity can cause similar problems with bacteria and mold growth in the building. As the winter air in Fairbanks is so cold and dry, it is usually difficult to attain anything close to 50 percent humidity in a properly ventilated house.

To keep condensation off windows, make sure your home is properly ventilated.

The presence of excess moisture around windows is a good indicator of the effectiveness of ventilation in your home. Shoot for the low end of the target humidity range, to keep both you and your home healthy.

Q: Can I face repercussions if my home is violating building code or it is out of date?

In Fairbanks, building inspectors primary focus is on new construction and remodels. When you are remodeling a home that is not built to code, inspectors only require that any new work meets current code.

Older parts of a building that are not involved in the remodel are not subject to same requirements, unless the inspector sees a situation that could jeopardize the life and safety of the occupants.

When it comes to code compliance, it is important to be aware that building codes are updated and revised on a regular basis. If your home is not up to date, do not panic.

Inspectors are not police that travel around town making sure residents bring their houses up to code. But remember, building codes exist to ensure the health and safety of the occupants, so a compliant house is a safe house. Furthermore, if you plan on selling your home, a buyer or lender may want an inspection before the sale is final. Any code violations will likely have to be corrected at that time. It would be better to deal with those issues before selling your home.

Alaska HomeWise articles promote home awareness for the Cold Climate Housing Research Center (CCHRC). If you have a question, e-mail us at You can also call the CCHRC at (907) 457-3454.