Excess Inventory

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Condensation FAQ

Q: Do windows cause condensation?
A: A window does not cause condensation.  It provides a ready medium on which vapor can condense.  The primary cause of condensation is excessive moisture in the air.  Windows are simply indicators of the moisture.

Q: Why do I see condensation on my windows and patio door first?
A: Condensation is generally seen first on windows and patio doors because they tend to have the lowest temperatures of any of the visible surfaces in the home.

Q: Are windows the only place where condensation forms?
A: Possibly no.  There's a point between exterior and interior walls that's just as cold as the inside window surface.  Chances are, if you see condensation on your windows, it's also forming between the walls.  Room-side surface of exterior walls are possibly warmer, but occasionally condensation occurs on cold spots such as nail heads and in the corners of outside walls and closets.  That's because insulation is weaker and circulation is restricted in those areas.

Q: What causes condensation on windows and patio doors?
A: Remember cool air can't hold as much moisture as warm air can.  So when the warm, moist air of the room comes into contact with the cold glass surface, some water vapor which the cooled air can no longer hold is deposited on the glass.  Condensation can also occur when the flow of warm room air over window surfaces is restricted.

Q: Does the amount of condensation depend on window type?
A:  Sometimes.  Angle, bay and bow windows, for example, usually experience more condensation than other window styles.  This is because inside air circulation around those types is usually more restricted.  Since they hang away from the insulated house wall, bays and bows could be a few degrees cooler in temperature.  To diminish excessive condensation, it's smart to insulate between the window head and platform, as well as between the seat and platform.  In extremely cold climates, additional insulation above and below the window platform may also be necessary.  As a secondary measure, placing a common electric fan near the window to promote air circulation may also be helpful.

Q: Do drapes and window shades cause window condensation?
A:  Drapes and other window coverings don't cause window condensation, but they can contribute to the problem by restricting the flow of warm room air over the glass surface.  Therefore, condensation is more apt to occur when drapes are closed and shades are pulled down.  Today's heavily insulated drapes and tighter shades can contribute to the problem even more.

Q: Why do I have condensation on my windows and my neighbor doesn't?
A:  The typical family of four produces 12 lbs. of moisture per day just breathing.  Washing dishes for 3 meals per day produces a pound of moisture.  One shower can add ¼ lb.  It is not unusual for a family of four to contribute 15 to 20 lbs. or 1 1/2 to 2 gallons of moisture per day to their indoor environment depending on their habits.  Indoor temperature, ventilation, air exchange and floor plan are also factors.

Q: What damage can excess window condensation do to windows?
A:  It can cause the paint to peel from the sash or stain the inside.  Water can run down into and cause dampness around the window frame.  It can sometimes cause paint to peel on the outside of the window.  As part of regular home maintenance, these areas should be cleaned regularly.

Q: Are there any cases where window condensation is only temporary?
A:  Yes, there are primarily three: new construction or remolding, the beginning of each heating season and quick changes in temperature.

• Wood, plaster, cement and other building material used in new construction and remolding produce a great deal of moisture.  When the heating season starts, this moisture will gradually flow out into the air in the home.  It will usually disappear during the first heating season and not cause any further trouble.
• At the beginning of the heating season, there may be a certain amount of temporary condensation.  During the humid summer, your house will have absorbed some moisture. After the first few weeks of heating, it will dry out, and you'll have fewer condensation troubles.
• Sharp, quick drops in temperature can also create temporary condensation problems during heating season.