Every area of your home is effected by attic moisture content, temperature, and air movement. Houses are constructed much “tighter” today than they were 20 or 30 years back. Windows are more effective, house wraps are now traditionally used, the R value of insulation has escalated, overall, our homes are more weather-tight. In doing this we trap the humidity inside the home. Interior humidity is produced by several things.
The normal perspiration and breathing of a family of four adds about 1/2 pint of water to the air just about every hour. Cooking three meals a day adds four or five pints of water to the atmosphere. Each shower contributes 1/2 pint. In fact, each individual activity that uses water, (like dishwashing, mopping floors, doing laundry) adds moisture content to the air. Specialists say that the daily living activities of a family of four can add more than 18 gallons of water a week into the atmosphere of a home. Air moisture will circulate toward drier air to equalize itself. This equalization process basically forces the indoor moisture content through the ceiling and insulation toward the attic locality. Ventilation of your attic is vital for two reasons. During the summer months, excess heat that accumulates in the attic during the day results in high energy costs for cooling, or uncomfortable living conditions.
Also, moisture produced within the home may move toward the attic if ceiling vapor barriers are not utilized, and they quite often are not. If this moisture is not exhausted from the attic it will condense and lead to insulation and construction materials to deteriorate, or cause mold or mildew to develop. So, temperature and moisture control are the main reasons for accurate attic ventilation. How much attic ventilation is enough? The most ventilation is necessary to clear away heat in the summer months. Winter attic ventilation must be adequate to clear away moisture vapor moving from the living space to the attic. In general, ventilation adequate for summer cooling is more than adequate for winter ventilation. Studies indicate that further increases in ventilation are not helpful in significantly lowering attic temperatures.
If the ceiling is inadequately insulated, you may need a little extra ventilation. Attic ventilation can be achieved by gravity ventilators, wind assisted ventilators or power ventilator. Regardless of the method used, the purpose is to provide uniform ventilation of the attic for proper temperature and humidity control. Natural ventilation is the most common and energy-efficient method of attaining attic temperature and moisture control. It is also the most economical, and my personal preference. If a space has high air outlets in conjunction with low inlets, ventilation takes place as the air present in the space is warmed. We desire to accomplish this with the application of eyebrow vents, stationed at optimal spots.