There are basically 3 types of roof “leaks” which are detailed below. The solution to your roof moisture issues depends on what type of “leak” it is. If you notice excessive moisture during extreme temperature changes, and not when it rains, then the moisture probably isn’t a roof leak. The following information should help determine what issues you might be experiencing and what you can do to alleviate condensation.

· The first type is where water is leaking through the roof system while it is raining. This could include leaks due to damaged or deteriorated shingles, improper installation of the shingles, or poor/failed flashing details at penetrations and walls. It may even be due to damaged window sills, improper siding installations or severe wind driven rain. These are external leaks which can usually be inspected and repaired by a roofer.

· The second type of “leak” is caused by ice dams. This is not workmanship related. The best way to prevent or reduce ice dams is to eliminate or reduce the amount of warm air that is escaping into the attic and melting snow on the roof to the point where it creates glacier like ice build up. Another temporary solution is to remove the snow from the roof before it can turn into ice and penetrate the roof system.

· The third type of “leak” is caused by condensation or frost buildup in the attic. This is not workmanship related or an actual roof leak. To prevent frost & condensation from developing in your attic you must eliminate or reduce the amount of air leakage into the attic as well as improve insulation & ventilation to allow moist air to escape the roof.

What is Condensation?

Condensation comes from the moisture in the air and is caused by too much moisture in the air for a certain temperature. Condensation forms when warm, moist air touches a surface that is colder than the dew point of the warm air. As that air becomes colder and its temperature drops below its dew point, it must release excess moisture to reach its new, lower dew point. It releases moisture in the form of water, which appears on the colder surface.

There are many things in our homes that put moisture into the air. Normal breathing and perspiration adds 3 pints of water to the air every day for each person in your home. In fact, every activity that uses water adds more moisture to the air including cooking, taking showers, dish washing, and doing laundry. Condensation is more apt to occur in climates where the average temperature is 35º F or colder. Condensation is a common sign of inadequate insulation and/or ventilation.

Condensation in the Home - A Warning Sign

Condensation is usually first noticed on your windows and skylights because they are the most visible areas of your house. While it’s natural to blame the windows, you shouldn’t always. Window and skylight condensation is the result of excess humidity in your home. And the glass only provides a visible cold surface on which humidity can condense. This could be a sign that your excessive indoor humidity is causing damage elsewhere in places you cannot see, such as: your walls, ceilings, floors, and your attic roof. Excessive indoor humidity can cause blistering and peeling paint, warping and rotting wood, as well as the formation of mildew & mold.

During extreme cold temperatures, frost can build up on the underside of the roof sheeting (attic roof). Once the outdoor temperature rises, that frost melts and can mimic a leak. This “leak” can be excessive when the temperatures dramatically change, as is common during our Alaskan winters. Frost build up is most common above heat sources such as light fixtures (especially can lights), kitchen stoves, fireplaces, bathrooms, fans, and improperly vented exhaust fans. When the frost melts, this “leak” is most commonly found dripping out of those heat sources.

High ceiling beams and cathedral ceilings with water spots can be confused with an active leak, when in fact it is a result of condensation.

If you have ever noticed a lot of icicles hanging from the edge of your roof, chances are your house is leaking significant (and expensive) amounts of air and heat into the attic.

Controlling Indoor Humidity

Most new homes are now made tighter than ever. They are well insulated and no longer "breath" on their own. Both insulation and ventilation should be addressed to control condensation. Steps must be taken to ventilate the house, allowing moisture and humidity to escape.

Steps you can take to control the humidity in your home include:

Bathroom and kitchen exhaust fans, as well as dryer vents, should never be discharged into the attic space, always discharge outside. You may have an
adequately ventilated attic, but this won’t matter if the bathroom exhaust fan dumps warm moist air directly into the attic space. This will result in condensed water vapor freezing onto cold attic materials, which will eventually thaw creating wet attic materials resulting in damage in the attic and inside the home.
Installing 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. Dehumidifiers are an inexpensive way to reduce the moisture in your home. Highly recommended in vaulted roofs with a loft.
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 crawl space.
Research shows keeping the attic air temperature below freezing when the outside air temperature is in the low 20s can reduce the occurrence of ice dams. Proper attic ventilation is key to keeping the attic cool, while adequate and properly installed insulation is key to keeping your house warm. It is critical to keep soffit vents free from obstructions to allow the natural flow of cool outside air into the attic space to replace the warmer attic air that rises and flows outside ridge and/or roof vents. This flow of air will keep the attic cool and free of moisture build-up.
Adding additional roof vents, such as box vents, turbine vents and ridge vents will also allow the warm air to escape the attic space and reduce condensation issues.