Taylors Windows® Greenville SC

Understanding Window Condensation: Causes, Effects, and Solutions

Windows are an essential component of any home, providing light, ventilation, and views of the outdoors. However, they can also be a source of frustration when condensation forms on them. In this blog, we will delve into the causes, effects, and solutions to window condensation, and dispel the misconception that windows cause condensation.

Defining the Problem:

Window condensation is the accumulation of water droplets on window surfaces. It can manifest in various forms, including interior condensation, exterior condensation, and condensation between window panes. While often viewed as a problem with the windows themselves, condensation is actually an indicator of excess moisture in the air.

Identifying Signs of Condensation:

So what are the signs you should be looking for in your windows? Here are a few things to keep an eye out for:

Interior Condensation:

  • Water droplets on the interior surface of windows.
  • Fogging or misting on glass.
  • Dampness or water pooling on window sills.

Exterior Condensation:

  • Water droplets forming on the exterior surface of windows
  • Typically occurs in cold weather when the glass surface is colder than the surrounding air

Condensation Between Panes:

  • Foggy or hazy appearance of windows
  • Water droplets trapped between the glass panes
  • Condensation that can’t be wiped off

Causes of Window Condensation:

Window condensation could be harmful if it isn’t addressed. Most of the time, people don’t know what causes the condensation in their windows and other aspects of their home. Let’s take a look at some of the most common culprits in causing condensation:

Indoor Humidity Levels:

  • Excess moisture from everyday activities such as cooking, bathing, and breathing can elevate indoor humidity levels.
  • According to the Environmental Protection Agency (EPA), the ideal indoor humidity level is between 30% and 50%.
  • On average, indoor humidity levels in American homes range from 20% to 60%.

Temperature Differences:

  • When warm, moisture-laden indoor air comes into contact with cooler window surfaces, condensation occurs.

Poor Ventilation:

  • Inadequate ventilation traps moisture indoors, leading to condensation.
  • Common ventilation issues include a lack of exhaust fans in kitchens and bathrooms.
  • Proper ventilation is essential for maintaining indoor air quality and controlling humidity.

Window Quality and Seals:

  • Drafty or poorly sealed windows allow warm, moist air to escape, reducing the likelihood of condensation.
  • New energy-efficient windows, while reducing energy loss, can also lead to condensation as they prevent air leakage.
  • Damaged or deteriorating window seals can also contribute to condensation by allowing moisture infiltration.

Effects of Window Condensation:

Damage to Window Frames and Surrounding Areas:

  • Prolonged exposure to moisture can lead to rot, decay, and mold growth in window frames and surrounding walls.
  • Over time, moisture damage can compromise the structural integrity of the home.

Mold and Mildew Growth:

  • Condensation provides an ideal environment for mold and mildew to thrive, posing health risks and causing unpleasant odors.
  • Mold and mildew can exacerbate respiratory issues and allergies, particularly in individuals with sensitivities.

Impact on Indoor Air Quality:

  • Excess moisture in the air can worsen indoor air quality, leading to respiratory problems and other health issues.
  • Condensation on windows is often a visible sign of poor indoor air quality and high humidity levels.

Decreased Energy Efficiency:

  • Condensation on windows could impact your energy usage and monthly bills. If your windows aren’t properly insulating your home or allowing air to pass through, it could mean your air conditioning or heat is having to run more thereby increasing energy costs and consumption. 
  • Energy-efficient windows can help reduce condensation by minimizing temperature differences and preventing air leakage.

Understanding New Energy-Efficient Windows:

Many homeowners are surprised to find condensation on their new energy-efficient windows. This is because the old windows were drafty or allowed for energy transference, which concealed the moisture problem. The new windows, with their improved insulation and sealing, prevent air leakage and energy loss, thus revealing the existing moisture issue.

Solutions to Fix Window Condensation:

Controlling Indoor Humidity:

  • Use a dehumidifier to maintain optimal indoor humidity levels between 30% and 50%.
  • Ventilate high-moisture areas, such as kitchens and bathrooms, with exhaust fans.
  • Avoid overwatering houseplants and using uncovered aquariums, as these can increase indoor humidity levels.

Improving Ventilation:

  • Ensure proper ventilation throughout the home by opening windows and using exhaust fans.
  • Consider installing trickle vents or mechanical ventilation systems to improve airflow.
  • Regularly clean and maintain ventilation systems to prevent blockages and ensure optimal performance.

Upgrading Windows:

  • Replace old, single-pane windows with energy-efficient double or triple-pane windows.
  • Choose windows with low-E coatings to reduce heat transfer and condensation.
  • Consider installing awning or casement windows, which provide better ventilation and airflow control.

Repairing Window Seals:

  • Inspect window seals for damage or deterioration and repair or replace them as needed.
  • Ensure that windows are properly installed and sealed to prevent air and moisture infiltration.
  • Consider applying weatherstripping or caulking around windows to improve insulation and reduce condensation.


Window condensation is a common problem faced by homeowners, but it is often a sign of an underlying moisture issue rather than a problem with the windows themselves. By understanding the causes of condensation and taking proactive measures to control indoor humidity and improve ventilation, homeowners can prevent damage to their windows and maintain a healthy indoor environment.

Additional Resources: