Condensation
		What is condensation, and what can I do about it? Condensation occurs when humid air comes in contact with a surface that is cooler than the air itself. In winter, when your high-quality vinyl windows are efficiently keeping cold air out and warm moist air in, condensation may appear as fog or moisture on the glass. Condensation does not indicate a problem with your windows; quite the contrary. It means you're holding in warm air like never before. But you're holding in humidity, too. That's the problem. You create humidity every time you cook, shower, clean, or merely breathe inside your home. Other contributors to household humidity are humidifiers, water pans on radiators or wood stoves, kerosene heaters, drying laundry, and house plants. The basic rules of thumb says that at 20 to 40 degrees outside and 70 degrees inside, the humidity in your home must be below 40% to avoid condensation. At 10 to 20 outside, your humidity must be below 35%. Here's what you can do to reduce the humidity that causes condensation: When using your bathrooms, kitchen or laundry room, turn on any built in fans. It is also a good idea to install an exhaust fan in your attic. Use a dehumidifier to remove excess moisture from the air. Every day, open a door or window briefly to air out your home. Opening fireplace dampers and basement or attic louvers will also work. In cold weather, move your house plants to a seldom-used room. Waterproof your basement floors and walls with moisture-sealing paint. Why is there condensation on my windows? Condensation on interior surfaces of windows and doors occurs because of high humidity and insufficient air exchange inside the home. In many older homes there were gaps in the windows where drafts could be felt and air would flow. This exchange of air, in many cases, was sufficient enough to prevent condensation from forming. The high-performance windows of today are designed to be air tight to reduce heat loss. This reduces air flow windows. Again, this is not a window defect. Condensation on exterior surfaces of windows and doors occurs because of the increased efficiencies in today's windows. On clear nights with still, humid air, condensation occurs when moisture-laden air comes in contact with a glass surface that is below the dew-point temperature. Dew-point is the temperature at which the air will no longer hold its' moisture vapor. Cold air holds less moisture vapor than warm air. In high-performance windows with Low-E and argon gas, the outside glass surface will actually be colder than a similar, "regular" window without these features. This is because the high-performance window is reducing heat flow to the outside and preventing the warming of the exterior surface above dew-point. This is not a window defect; like dew forming on grass and car-hoods, it is a natural phenomena. Other factors that influence condensation: Window Size: Larger windows may have a higher tendency to show condensation. Window Location: Windows protected from the wind will have a higher tendency to show condensation. Screens: Windows protected by exterior screens may have different condensation than the same windows without screens under the same conditions. 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. Interior Shades: Opening interior shades or blinds may reduce condensation by allowing more heat to transfer to the outside. Minor differences in conditions can cause condensation to form on one window and not on another, even when they are side-by-side. Finally, condensation on windows can be a seasonal or a night-time event. When outside temperatures are warm, the glass temperature will usually be above dew-point. The same is true during cold, winter weather. Condensation will most often occur during transition months.