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energy efficient windows condensation: Causes and Solutions

Energy efficient windows are a practical and cost-effective way to reduce energy loss, enhance comfort, and improve indoor air quality. They are designed to keep the outdoor temperature from affecting the indoor temperature by minimizing heat transfer through the glass, frame, and seal. However, some homeowners may notice condensation on their energy-efficient windows, which can be a cause for concern. This article discusses the causes of window condensation, how it affects energy efficiency, and how to prevent or reduce it.

Condensation Occurrence

Condensation is the process by which water vapor changes from a gas to a liquid state. When the indoor air has high humidity, and the temperature of the glass surface drops below the dew point, condensation occurs. This happens when the temperature of the interior side of the glass is lower than the dew point of the air. The dew point is the temperature at which water vapor in the air becomes saturated and forms dew or fog.

Causes of Window Condensation

Several factors can increase the likelihood of condensation on energy-efficient windows. These include:

1. High humidity levels: If the indoor air contains excess moisture, it can create condensation on the windows. Cooking, bathing, laundry, and indoor plants are some of the sources of moisture in a house.

2. Poor ventilation: Inadequate ventilation in a home can trap humid air and cause condensation to form on windows.

3. Cold outdoor temperatures: When outdoor temperatures drop to low levels, they can create a larger temperature difference between the glass surface and the indoor air, causing condensation to occur.

4. Poor window insulation: If the window seal is defective or the frame is poorly insulated, cold air from the outside can infiltrate the indoor space, causing the glass surface to become colder and allowing moisture to condense.

Energy Efficiency Impact

Window condensation can affect the energy efficiency of a home in various ways. Firstly, it can cause damage to window blinds, frames, and sills. Secondly, the accumulated moisture can create a breeding ground for mold and bacteria, which can harm the indoor air quality and lead to health issues. Thirdly, window condensation can reduce the thermal efficiency of the window, leading to higher energy consumption and increased energy costs.

Solutions and Prevention

There are various ways to prevent or reduce window condensation in a home. These include:

1. Reducing indoor humidity: Maintaining indoor humidity levels below 50% can help prevent window condensation. Using exhaust fans, proper ventilation, and dehumidifiers can help reduce excess moisture indoors.

2. Improving ventilation: Proper airflow is essential to prevent excess humidity buildup. Homeowners can open windows and doors, use exhaust fans in bathrooms and kitchens, and ensure that the HVAC system is working correctly.

3. Installing storm windows: Storm windows can create an additional layer of insulation, which can help reduce the temperature difference between the glass surface and the indoor air.

4. Upgrading window insulation: Poorly insulated windows can allow cold air to infiltrate the interior space. Homeowners can improve the insulation by adding window film, weather-stripping, or replacing the window completely with a higher efficiency model.


Energy-efficient windows offer numerous benefits, including cost savings, improved comfort, and environmental friendliness. However, window condensation can occur and affect the energy efficiency of a home. By understanding the causes of window condensation and implementing proper prevention and solution measures, homeowners can maintain the energy efficiency of their homes, prevent damage to their windows, and enhance their indoor air quality.