Condensation on Vinyl Replacement Windows

What It Is – and What You Can Do About It

Replacing drafty windows with Vytex’s high-performance vinyl windows will reduce airflow in your home and make it ‘tighter.’ And while tighter homes retain warmth, they also retain humidity, causing fog or dew to appear on vinyl replacement — and all — windows, usually in the colder months. This condensation usually appears near the bottom of the window sash, because the glass near the sash is the coolest surface. Condensation is not indicative of a problem with your new windows’ installation or construction—rather, it’s a testament to their superior efficiency.

A little condensation is normal and will not damage your new windows or home. It simply means that the humidity in your home is too high, and you need to reduce it until the condensation disappears.

Here are steps you can take to reduce condensation by controlling humidity and increasing air movement in your home:

  • Use exhaust fans in your kitchen, laundry room, and bathrooms. Consider installing an exhaust fan in your attic to draw out moist air.
  • Use a dehumidifier and discontinue using furnace humidifiers and other humidifying devices.
  • Air out your house for a few minutes each day by opening a window or exterior door.
  • Vent gas burners, clothes dryers, etc. to the outdoors.
  • Be sure that the ventilating louvers in your attic, basement, or crawl spaces are open and amply sized.
  • Open fireplace dampers to allow moisture-laden air to escape.
  • Move houseplants to a sunroom or other infrequently used room.
  • Waterproof your basement floors and walls with moisture-sealing paint and moisture barriers.

If condensation covers the entire window and drips down the walls, ruining the paint, plaster, or wallpaper, you may have a problem that requires the attention of a professional who can determine how to improve your home’s ventilation. Contact an architect or HVAC contractor for additional solutions.

Condensation Occurrences

Outside Air Temperature Inside Humidity at which Condensation Occurs
20° Over 35%
Over 25%
-20° Over 15%

The values in this chart are based on winter conditions of 70° indoor temperature with 15 mph outdoor winds and double-glazed, vinyl replacement windows.

Learn more about window condensation by downloading this brochure.

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