Roof Venting Guidelines

Proper Ventilation

• Regardless of the region in which you live, ventilation of your home is important, especially on the roof. Creating the appropriate ventilation includes circulating the air in and out of the house. The air circulation quotient ideally needs to be at equal parts intake and exhaust. For instance, you need the same amount of vents that bring in fresh air from outside as you do exhaust vents releasing air from the house. Most intake vents are located under the eaves to draw in the air, while the roof ridge vent allows air to escape.

Attic Moisture Buildup

• Heat rises, and warm air has more moisture content than cooler air. Because of this, your house's attic is a natural depository of excess moisture in warmer air. Without the proper roof ventilation, it accumulates in the attic and may form condensation, which leads to further damage to walls and ceilings within the home. Roof vents in the proper ratio to allow good air flow alleviate this problem.

Quantity

• To maintain the proper equal intake to exhaust ratio for maximum air circulation, for every 300 square feet of attic space, 1 square foot of ventilation is recommended. This is a code in certain regions and a general guideline in others. Professional roofers recommend a continuous roof ridge vent and soffit ventilation system. By drawing air in through the soffits and directing the exhaust up through the ridge vent, it creates a flow up across the entire roof.

Weather Infiltration

• Natural elements, like the wind, also have an influence on roof ventilation systems. A negative air pressure system is created when wind blows across the roof. Nature compensates for this negative air pressure and brings in high pressure air from a different location. Unfortunately, higher pressure air exists in an attic, and without the proper intake ventilation to replace it, air will come in through the exhaust vents. At times, this air will contain moisture and potentially cause damage.