Why Are My Windows Sweating?

In the dead of winter, you pull back the curtains to find the glass dripping wet. This is Interior Condensation. It happens when warm, moist air from your home hits the cold surface of the glass.

Is it a Defect?

No. Interior condensation actually means your windows are doing a good job of sealing the house. The moisture is trapped inside with you. Note: If condensation is BETWEEN the two panes of glass, that IS a seal failure. You need new glass.

The Causes

1. The "Tight House" Effect: Modern homes are sealed so well that moisture from cooking, showering, and breathing has nowhere to go.
2. Nighttime Drop: Blinds and curtains trap cold air against the glass, lowering the surface temperature below the "Dew Point."

The Fixes (Ranked by Cost)

1. The Hygrometer (Cost: $10)

Buy a cheap humidity monitor. In winter, your indoor humidity should be 30% - 40%. Anything over 50% guarantees wet windows.

2. Air Movement (Cost: Free)

• Run the bathroom fan for 20 minutes after showering.
• Run the kitchen hood while cooking pasta.
• Leave curtains open a crack at night to let warm air circulate against the glass.

3. The Dehumidifier (Cost: $200)

If you have a damp basement or cook a lot, a dehumidifier is the nuclear option. It will dry out the air and stop the sweating overnight.

4. Upgrade the Glass (Cost: $$$)

Double or Triple-pane windows have "Warm Edge Spacers" and Argon gas that keep the interior glass warmer. Warmer glass = No condensation.