Care & maintenance
About Condensation
The insulating properties of the glass used in energy efficient windows can cause condensation to collect on the glass under certain environmental conditions. Learn more about what causes condensation below.
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Interior Condensation
Condensation on interior surfaces of windows and doors occurs because of high humidity and low air exchange inside the home. This exchange of air, in many cases, was sufficient to prevent condensation from forming. The high-performing energy efficient windows and patio doors of today are designed to be air tight to reduce heat loss, which can result in reduced air flow. You can combat interior condensation by reducing moisture sources (humidifiers, aquariums, etc.), increasing ventilation (open windows for a few minutes each day), and leaving closed interior shades up a couple inches above the window sill to allow for air movement between the shades and the window.
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Exterior Condensation
Exterior condensation results from the same environmental conditions that cause condensation or frost to appear on a car that is parked outside overnight. It forms when moist air comes into contact with cool surfaces such as glass. This can happen when a cool night follows a warmer day, typically during the spring and fall seasons. Condensation generally does not occur with less energy efficient windows, because heat from the warm interior of the home escapes through the window keeping the exterior temperature of the glass high enough to prevent condensation.
Energy efficient windows significantly reduce the interior heat conducted through the glass, which lowers the temperature of the outside glass. Exterior condensation is actually an indication that the insulating glass in your windows is performing as it should, reducing heat loss and lowering utility costs. It is a result of the normal functioning of energy efficient windows.
Other Factors
Weather Changes: Condensation can be a seasonal or a night-time event. When outside temperatures are warm, the glass temperature will usually be above the dew-point. The same is true during cold, winter months.
Moisture Between Panes: Moisture that builds up between the panes of glass may be due to a failed insulating unit, and if so it should be repaired.
Window Size: Larger windows may have a higher tendency to show condensation.
Window Location: Minor differences in conditions can cause condensation to form on one window and not another, even when they are side-by-side. Windows protected from the wind will have a higher tendency to show condensation.
Air Circulation: Good air circulation, such as exposure to wind, reduces the occurrence of condensation. Building projections, foliage and other wind-breaks may contribute to condensation.
Screens: Windows protected by exterior screens may have different condensation than the same windows without screens under the same conditions.