It's hard to believe, but a family of four can generate up to 18 gallons of water in the form of humidity inside a home in a week? Cooking, showering, washing and drying clothes, and even breathing, creates a lot of water and it has to go somewhere. Your windows are usually the first place you will see evidence of moisture resulting from high humidity in a home. Here in the Rochester MN area, the colder it is outside during the winter, the more evident high humidity will be. This does not mean there's a problem with your windows. The majority of window condensation simply indicates that your home needs increased ventilation to lower the amount of moisture in the air or you need to reduce the sources of the humidity. I did a home inspection on a home recently where there was a concern with the sky lights and moisture. Turns out that the humidifier has malfunctioned and the humidity was near 60%. The humidifier was disabled, and within a day or so, the windows dried up.
Older homes tend to have more cracks in their construction, allowing "natural" air infiltration into the home and help reduce moisture. Newer homes, however, are much tighter and therefore tend to trap moisture in. this is helpful from an energy efficiency standpoint, but contributes to condensation and creates the potential for condensation on surfaces that are cooler than the dew point.
Humidity is generated by cooking food, running the dishwasher, filling the sink with hot water, showers, hot tubs, washers and indoor-vented dryers, basements and crawl spaces that channel dampness from the ground into the home, breathing and perspiration.
Other than these perpetual sources of moisture, wood, plaster and other building materials in a new home will absorb moisture during humid summers and gradually release it after the first few weeks of heating your home in the fall.
Can this damage my windows?
The occasional moisture condensation on the glass after a hot shower, or when steaming food on the stove usually aren't a problem. However, if your windows are "sweating" without cause or for long periods of time, your windows could become damaged. Wood frames and sash can warp and become difficult to operate. Paint or other finishes may peel or become discolored. Other areas of the home could also be damaged, such as insulation, exterior siding and drywall.
What Can I Do?
Decrease the amount of moisture in the air that can condensate on windows is the first step. You may have to add ventilation, eliminate sources of humidity or remove humidity from the air after it's been generated. To lower the humidity in your home, you need to increase ventilation and decrease the sources of moisture.
Run exhaust fans in the bathroom during a shower, or in the kitchen while cooking.
Take shorter showers and install water-restricting faucets - you'll lower your humidity and your water bill.
Use the microwave, slow cooker, or outdoor grill more frequently.
Check and reroute drainage away from your home to minimize the moisture in and around the basement and foundation.
Run a dehumidifier in basements and other damp areas.
Turn off your furnace humidifier or other home humidifier.
Open drapes and blinds to allow warm house air to circulate across the windows.
Are All Windows Affected by Condensation?
Condensation will appear on any type of window, if a home has high humidity. Vinyl, wood or aluminum windows, regardless of manufacturer, will have some condensation if the air is humid.
One component in standard dual-pane glass, or insulated glass, can help minimize condensation. The adhesive spacer that bonds together the two panes can help reduce condensation if it is comprised of a non-metal material. Traditionally these spacers have been made of stainless steel or aluminum, both of which conduct heat and cold readily. A non-metal spacer minimizes conductivity and, in turn, reduces condensation. "The non-metal, spacer system also improves the energy efficiency of windows while reducing condensation. The less metal a window has, the less it will conduct heat and cold, the less condensation will appear on the glass, and the more energy efficient it will be