Condensation forms on glass whenever the temperature of its surface becomes less than its dew point temperature. The dew point temperature of a window changes based upon the amount of humidity in a room. So, in rooms with high humidity, like your bathroom or kitchen, you’ll often find a thin layer of moisture coating the insides of your windows.

Though this phenomenon is commonplace, excess moisture accumulation can pose a threat to the structural integrity of your windows and home. Surplus moisture can seep into your windows’ frames and their surrounding walls, producing mold and causing structural problems.

Fortunately, certain windows are designed to more efficiently resist condensation formation. In order to best maintain the structural integrity of your windows and home, you should take condensation resistance into consideration when choosing windows.\

Structural Risks of Excess Condensation

 Windows are easy points of entry for cold air and moisture. When these intruders come into contact with high humidity, condensation forms. The accumulation of too much condensation upon your windows can lead to far graver issues than obscured views.

Excess condensation can infiltrate window frames, ruining finishes, causing discoloration, and weakening their wood. If moisture finds its way into your walls or surrounding woodwork, it can get trapped there and cause water damage. Worse yet, under certain conditions, this moisture can freeze and create buildups of ice, which can drain into your walls and diminish your home’s structural integrity.

Moisture intrusion can also create a breeding ground for bacteria. The accumulation of mold and mildew can deteriorate the structure of your walls in addition to posing health threats.

CR Rating

To help you find windows that resist condensation well, the National Fenestration Rating Council (NFRC) sometimes includes CR ratings on their window labels. These ratings, however, are optional, so not every window you come across will have one.

Expressed as a number between 1 and 100, CR measures the potential for condensation formation on the inside of a window. The higher the number, the better the window is at resisting condensation. The rating is derived from a series of tests examining the minimum performance of different components of the window assembly, including its center-of-glass, edge-of-glass, and frame, across various temperatures and humidity levels.

Choosing Windows with Good CR

Windows with good CR experience less structural deterioration than those that accumulate a lot of condensation. The easiest way to find windows with good CR is to look for NFRC window labels that include CR ratings and choose a window appropriate to your household’s needs. As a rule of thumb, you’ll generally want to opt for a window with a CR rating greater than 50.

If CR ratings aren’t provided, choose windows that are thermally efficient to reduce the potential for excess condensation formation. The heat inside your home travels through the parts of your window that are least energy efficient, causing those surfaces to lose heat and allowing condensation to form.

By purchasing windows with low-e coatings, thermally-improved frames, or multiple-glazing or insulated glass units, you can keep your home energy efficient and defend it against the structural dangers of excess condensation formation.