What Will Happen If I Don't Ventilate My Attic?

Attic ventilation helps improve the energy efficiency of a home.

Proper attic ventilation is necessary to prevent damage to the structure of your home from mold and mildew. When there's excess moisture in the attic, mold and mildew form, which can cause respiratory problems if left untreated. As a result of poor ventilation, ice dams form due to uneven heat distribution or heat loss through the roof.

Ice Dams

An ice dam is defined as a blockage on the edge of the roof that prevents water or snow-melt from draining. An ice dam is formed when there is snow on the roof and an uneven distribution of heat along the roof's surface. For example, if heat loss occurs through the attic in the upper portion of the roof, with lower temperatures at the edge of the roof, water forms and runs down the slope, hits the cooler area and freezes. Poor attic ventilation allows heat to accumulate and causes heat loss through the roof, which potentially leads to the formation of ice dams.

Condensation

Condensation is another result of poor attic ventilation, and decreases the efficacy of the insulation. Condensation forms when air from the heated portion of the house flows into the unheated attic. Heated air contains levels of moisture that develop into water or condensation when coming in contact with unheated air. Depending on the moisture content, an accumulation of condensation can cause structural damage to walls and ceilings. By regulating the airflow in the attic with proper ventilation and reducing the moisture content in the air, condensation is kept to a minimum.

Mold

Poor attic ventilation is a contributing factor to mold forming in areas of high moisture. The extent of the mold infestation is based on the amount of humidity and moisture present. Proper ventilation and air flow lowers the chance of condensation forming and decreases the moisture content in the air. The natural flow of air is upward and outward; attic ventilation circulates the air in the attic and helps to dry the air enough to prevent the formation of mold.

Heat Loss

Proper attic ventilation draws heat away from the roof and redirects air flow to keep the house cooler in the summer and warmer in the winter. Building codes often regulate attic ventilation in newer homes in an effort to provide more heating and cooling efficiency. Natural ventilation such as Soffit vents and ridge vents may not always be adequate, depending on the type of structure and square footage. Attic fans are options to compensate for this inadequacy and benefit the integrity of the house.

References

• University of Minnesota Extension: Ice Dams; Timothy Larson, et al; 2009
• Ball State University: Indoor Environment Notebook; Thad Godish
• Cornell University Cooperative Extension: Causes and Cures of Attic Condensation and Roof Ice Damming Problems; Mark Pierce; February 2005
• North Dakota State University: Keep Your Home Healthy; Kenneth Hellevang; 2004