Windows Sweating?
The word "moisture" refers to water vapor mixed with air.  Most of the moisture generated in the
home is dissipated by the movement of moisture-laden air out of the home. As homes become
energy-efficient, the number of paths of escape are reduced, and dealing with moisture
becomes more important.

During the heating season, the indoor humidity level should hover around 30 percent to 40
percent. When indoor humidity exceeds 40 percent during cold weather, moisture problems
begin to appear. One symptom of a high humidity level is condensation forming on cold surfaces.
 High levels of humidity are often the result of too much moisture vapor generated indoors.  All of
this moisture MUST eventually escape from your home.
What causes window condensation and how to avoid it.
Window condensation
Window Condensation:
Condensation will occur whenever the window surface is cool enough to allow moisture in
the air to condense on it, which is why some condensation can be expected in the winter -
condensation should be controlled as much as possible since it can damage the window's
components, cause the wood to rot and saturate the wall insulation reducing its effectiveness.
(An example of condensation: A glass of ice water sweats because the warm air that
surrounds the glass meets the cold surface and guessed it, Condensation)

Moisture on the inside of the storm window (or outside pane).  Indicates that the prime window is
allowing air and moisture to leak out to the
storm window where it condenses. Stopping these air
leaks with caulk and weather stripping will stop the condensation and ultimately save your
window. It is also important to understand that too little humidity is bad for your house.
Manufacturers claiming that low humidity (15 percent) is best for windows may be covering
for a poor quality product. Good windows should not have excessive condensation at normal
humidity levels (30 percent to 40 percent).
Moisture on the inside of a window pane:
This is a sign that airborne water is trapped in
the house due to poor air circulation and

Moisture between single pane windows and
exterior storms:
Storm window frames are made with a
breathing hole that permits condensation to
escape. These breathing holes often become
plugged or puttied shut over time. When this
happens, moist air becomes trapped and
condensation appears. To fix the problem,
unplug the holes.

Steps to Reduce Excessive Humidity:
Recognize that the best way to stop
condensation is to reduce the moisture in the
inside air.
Here are a few tips:

Vent gas burners and clothes
dryers to the outside.

Dryer and kitchen range
exhaust fans should never be
vented to the attic.

Install exhaust fans in the
kitchen, bathrooms, and
laundry rooms.  

Controlling or covering other
sources of humidity (radiator
water pans, fish tanks, large
numbers of plants, etc.).

Installing a dehumidifier.  
Opening fireplace damper.  

Ventilating the crawl space or
basement:  Install foundation
vents or leave a basement
window cracked in the fall or
early winter to ventilate your
basement or crawlspace.

Another positive measure is to
connect a small duct from the
outdoors to the return side
of a forced-air heating system,
so that fresh air is drawn into
the house whenever the
system is operating. A damper
placed in this duct will allow the
home owner to control
incoming air.

A simpler method is to simply
crack a window somewhere in
the home.
Wall Insulation:
To prevent or reduce condensation problems
inside your walls and protect your insulation,
the side of the insulation exposed to high
vapor pressure (warm side in winter) must be
covered with material that will impede the
natural drive of moisture to flow through the
inside surfaces of exterior walls, toward the
lower vapor pressure outside.

To be effective, such a material must have a
high resistance to moisture flow. The material
is usually called "vapor retarder."
Window Condensation
St. Petersburg Replacement Windows, Tampa, Clearwater, Oldsmar, largo, Dunedin
Copyright 2012, Bayside Windows and Doors, Inc. / Shorian Construction All rights reserved.
Replacement Windows & Doors
Clearwater, St. Pete, Tampa
(727) 504-2383
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