What Window Condensation Means and How to Prevent It

June 5, 2015

If home window condensation happens once, it usually happens again and again. It’s more often an ongoing issue with your indoor environment rather than something wrong with your windows. Here’s the science behind it.

How Home Window Condensation Occurs

Wherever warm, moist air meets a cool, solid surface, condensation can occur. In the average home, what’s the coolest surface in the house? Surprisingly, it’s usually the glass window panes. Glass is an effective heat conductor. Maybe you’ve noticed how window glass almost always feels cool to the touch. When overly humid household air contacts cool, slick glass, condensation appears as fog, water drops or streaks.

Effects of Window Condensation

The downsides of perpetually wet windows are numerous:

  • A room without a view – Instead of a crystal clear panorama, you’ve got a murky, streaked perspective on the outside world.
  • Windows don’t stay clean – Wet windows attract dirt and dust and always appear grimy. Regular cleaning can’t keep up with condensation spots and streaks.
  • Sill and sash deterioration – Condensation dripping from window panes keeps wooden components like the window frames, sill and sash continuously damp. Paint peels and exposed, saturated wood slowly rots. Windows may stick and be difficult to open.
  • A home for mold and mildew – Dormant mold spores are all around your house, just waiting for a dependable source of moisture to activate and start dispersing reproductive spores into your indoor environment. Toxic mold growth on wet windows commonly manifests as a black residue around the perimeter.

Why Is Indoor Humidity High?

The drafty homes of the past have been replaced by airtight, energy-conserving structures that let very little fresh air in, not to mention prevent  accumulating humidity from getting out. Within this enclosed indoor environment, water vapor often concentrates to levels that cause home window condensation. Here are some of the common sources:

  • Outdoor humidity intrudes each time an exterior door or window is opened, particularly in Florida’s climate.
  • Daily activities such as cooking and bathing also add to cumulative household moisture. Humidity originates in the kitchen from boiling water, as well as from the stove itself. Water vapor is a by-product of natural gas combustion. Bathrooms are another source. One hot shower can contribute 1/4 pound of moisture to the air.
  • The attic above and the crawl space below can act as permanent sources of infiltrating moisture.
  • Housekeeping contributes to indoor humidity. Wet clothes hung out to dry, mopped floors and other cleaning chores produce water vapor.
  • The number of occupants is a good predictor of the household humidity level, too, as every exhaled breath contains water vapor. A family of four adds four pounds of moisture to the indoor environment every day just by breathing.
  • Experts in the field also consider the number of house plants, as well as pet water bowls as additional contributing factors in indoor humidity.

How to Bring Indoor Humidity Down

When indoor relativity humidity is reduced, home window condensation diminishes. This requires a multi-faceted approach to deal with the multiple water vapor contributors listed above. Here are some ideas to dry out your indoor air:

  • Move humid indoor air outdoors. Utilize spot exhaust fans in the kitchen and bathroom. These fans must be vented all the way to the exterior of the house, not simply into the attic or wall voids.
  • Circulate air as much as possible with fans. Moving air lowers its water vapor content.
  • If the humidity level outdoors is low and weather otherwise permits, open windows to allow fresh air into the house.
  • Maintain your clothes dryer properly and make sure the vent is functional and not obstructed with lint.
  • Humidity naturally tends to migrate from a damp zone into a drier zone. Identify and seal structural cracks and gaps that allow water vapor from the attic or the crawl space to permeate the conditioned envelope of the home.
  • Verify that attic vents are unobstructed to maximize passive ventilation and reduce humidity. Install a vapor barrier over the crawl space floor to reduce infiltration of moisture from the soil.
  • Humidity reduction is an important part of the air conditioning process. Make sure your air conditioner is properly maintained with regular annual tune-ups.
  • Your HVAC contractor can discuss options like a whole-house dehumidifier for definitive control over indoor humidity levels. Installed in your ductwork, this unit treats the total content of air in the home as it circulates constantly through the duct and allows precision humidity adjustments with a digital humidistat.

Learn more about how to handle home window condensation, as well as indoor air quality solutions available from Ocean State Air Conditioning & Heating, or contact us today at (904) 574-5619.

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