A balanced attic ventilation system that consists of intake at the eaves, soffits, or facias of the roof, and exhaust at or near your roof ridge, serves two important functions. First, it allows cool, fresh air to enter into the attic. Second, it allows hot, moist air to escape.
Improper ventilation can contribute to heat and moisture buildup in the attic and can even increase the temperature in your living space. Excessive heat and moisture can cause damage to shingles, wood framing, ceiling, siding, paint, and wallpaper. Another effect of improper ventilation is that it may increase cooling energy consumption.
During the winter season, appliances as well as showers, baths, cooking, and laundry can contribute to extra moisture build-up and water vapor in the attic. When an attic is not properly ventilated, this moisture collects on the underside of the roof. Excess moisture can also cause damage to the structure of the house, like rotting, and can even attract wood-eating insects like termites.
How You Can Improve Your Attic Ventilation
The U.S. Federal Housing Administration recommends a minimum of at least one square foot of attic ventilation (split evenly between intake and exhaust) for every 300 square feet of attic floor space. This 1/300 rule is general and may not apply to all building.
If you are not sure if your attic is properly vented, or if you’ve had high cooling and heating bills in the past, now is the time to call a reputable roofing contractor in your area who will check your attic and roof to determine that you have the proper amount of ventilation your attic requires.
Source: https://modernize.com/home-ideas/25937/the-importance-of-attic-ventilation-2