PVC Windows and Icing Problems

How Condensation Forms

• Condensation forms when invisible droplets of water that are suspended in the air contact a much colder, solid object. While PVC windows tend to be less conductive, the glass portion of the window can still experience significant temperature fluctuation. No matter how cold a window is, though, condensation cannot form without humidity. Often a modern home is so tightly sealed that humidity can build quickly, especially when appliances come into the mix. When a humid air mass inside a home meets a window that has been significantly chilled by low outdoor temperatures, condensation and frost or ice formation will result.

Contributors to Interior Condensation

• Many modern appliances and household items can contribute to the humidity level of a house. Improperly vented ranges, ovens and dryers will add moisture to the air too. Less obvious sources of moisture include houseplants, frequent showers, vent-free fireplaces and aquariums. The foundations of many older homes are not sealed -- those materials can wick water from the soil into the house as well. Installing a dehumidifier can help you better control indoor moisture if your PVC windows are icing.

Choosing PVC Windows

• PVC windows vary greatly in their ability to resist condensation. Low-grade PVC windows look great and function perfectly well, but they are not energy efficient enough to prevent condensation when the weather turns bad. Some window manufacturers voluntarily certify their windows for energy efficiency; in turn, these more energy-efficient windows allow less transfer of outdoor temperatures and keep condensation in check. If you are looking to add vinyl windows to your building project, select ones certified by the American Architectural Manufacturers Association (AAMA), Energy Star or the National Fenestration Rating Council (NFRC).

Installation Woes

• Improper installation may be the culprit if your windows ice very easily. When vinyl windows are installed, they should be surrounded on all sides with insulation and sealed from the outside against air leaks. Incorrectly installed aluminum capping makes creating an effective caulk bead difficult. Another common installation problem occurs with brick homes. Capping can be improperly installed in such a way that it diverts water into the window rather than away from it, leading to rusting and allowing additional air to penetrate into the window or home.