The Truth About Window Condensation—and What You Can Do to Prevent It

When homeowners notice moisture collecting on their windows, it’s natural to worry. Is it a sign of poor product quality? Could it indicate a leak or damage? In reality, window condensation is a common issue that often signals something completely different—namely, high indoor humidity levels and a well-sealed home.

At NBP Windows & Doors, we believe in educating our customers so they can make confident decisions. Here’s the truth about window condensation, what causes it, when to worry, and—most importantly—how to reduce or prevent it.

What Is Window Condensation?

Window condensation is the appearance of water droplets, fog, or frost on the glass surface. This typically occurs when humid air comes into contact with a cooler surface, such as window glass. Condensation may form on the interior or exterior of a window, or in rare cases, between the panes of insulated glass.

Why Window Condensation Occurs?

Interior Condensation – This is the most common type of window condensation and occurs when warm, moist indoor air hits the cooler surface of the window glass. It’s often a seasonal issue—especially during the fall and winter months when indoor heating and tightly sealed homes reduce ventilation.

Exterior Condensation – This usually happens on the outside surface of your windows during the spring and fall, when outdoor humidity is high and temperatures are just right. This type of condensation is harmless and typically resolves itself as the day warms up.

Condensation Between the Panes – If you see moisture trapped between the panes of glass in a double- or triple-pane window, this may indicate a seal failure. In this case, the insulating gas (such as argon or krypton) may have escaped, and the window’s energy efficiency could be compromised. This type of condensation is covered under the NBP Limited Warranty in specific conditions and should be inspected by a professional.

When Is Condensation a Problem?

Not all condensation is cause for concern. Exterior condensation is purely cosmetic, while interior condensation is usually a sign of high indoor humidity—not faulty windows. However, if condensation persists or you notice mold growth, peeling paint, or moisture damage around the windows, it’s time to take action.

How to Reduce or Prevent Interior Window Condensation

While you can’t control the weather, you can take several steps to reduce humidity and limit condensation inside your home:

Use Exhaust Fans – Run exhaust fans in bathrooms, kitchens, and laundry rooms to remove excess moisture during daily activities.

Increase Ventilation – Open windows on mild days to allow fresh air to circulate. Consider installing trickle vents or mechanical ventilation systems to improve air exchange.

Use a Dehumidifier – In rooms with high humidity, especially basements or newer airtight homes, a dehumidifier can significantly reduce moisture levels.

Adjust Your Thermostat – Maintain a consistent indoor temperature and avoid overheating your home, especially during cold weather when condensation is more likely.

Limit Indoor Moisture Sources – Cover pots while cooking, reduce the number of indoor plants, and avoid drying clothes indoors.

Keep Drapes Open – During the day, open blinds or curtains to promote air circulation around windows.

How NBP Windows & Doors Can Help

All NBP windows are manufactured with high-quality insulated glass units (IGUs) designed to minimize heat transfer and improve energy efficiency. Our products include warm-edge spacer technology to help reduce the likelihood of condensation forming on the glass surface.

If you suspect a seal failure or want help identifying the cause of your condensation, we recommend contacting your remodeler or dealer for an inspection. If a covered warranty condition is found, they can assist in filing a service request with NBP Windows & Doors.

The Bottom Line On Window Condensation

Window condensation is not only common—it’s often a sign that your home is energy-efficient and well-insulated. But understanding the causes and how to manage humidity is key to protecting your home and comfort. By taking simple steps to control moisture, you can enjoy clear views and greater peace of mind.

For more tips on window care and to learn about NBP’s warranty coverage, visit nbpwindowsanddoors.com/warranty-information.