Why is there water on the windows inside my house? Condensation is the answer. Condensation is the process of moisture collecting on surfaces that are cooler than the surrounding air. During winter months you may notice moisture at your windows on especially cold days. HVAC systems only dehumidify the air when they are operating in cooling mode. When they are in heating mode, no dehumidification takes place. Because of this, the relative humidity in your home will be slightly higher at times during the winter. We can help you with some information about preventing condensation in your home.
When warm, moist air meets cool windowpanes, droplets form on the surface. In Tennessee, during hot and humid weather, you will find condensation accumulating on the exterior of windows. Often you will hear the weatherman refer to “dew point.” Dew point is the temperature when the air mass is fully saturated; relative humidity is 100% causing the water vapor to become a liquid. So, at 72° with relative humidity at 50% inside your home the dew point is 52.4°. Say that is the situation in your home and someone takes a shower and doesn’t use the exhaust ventilation and the home is now 72° with 55% humidity. Now your dew point is 55° and if your window surface temperature is 55° or below, you will have condensation. If you have a home temperature of 70° with 40% relative humidity your dew point is 44°. That means if your window surface temperature is 44° or less, your windows will sweat.