Proper ventilation is one of the most crucial factors in a roof’s durability. Without it, moisture and heat can accumulate in the attic area, causing the sheathing and rafters to rot, the insulation to lose its effectiveness, and the shingles to buckle.
Therefore, a professional roofing contractor will never recommend blocking off sources of ventilation such as soffit vents, ridge vents, and louvers – even during winter. Good ventilation in the attic also increases the life of the roofing material, prevents structural damage caused by moisture, enhances the comfort level in the rooms underneath, and reduces energy consumption.
In addition to the importance of free flowing air, a roofing contractor knows that insulation plays a vital role in attic ventilation. Ideally, an attic should have:
- At least 1 inch of space between the roof sheathing and the insulation.
- Enough vented, open spaces to enable air to pass freely in and out.
- A vapor retarder next to the ceiling and under the insulation to prevent moisture rising into the attic.
- A gap-free layer on the attic floor to protect the home from heat loss or gain.
The requirements for correct ventilation in an attic depend on a number of factors, including the structure’s atmospheric humidity, shade, and exposure to the sun. Nonetheless, the formula for ventilation is generally based on the width and length of the attic. The NRCA (National Roofing Contractors Association) recommends that a roofing contractor leaves at least 1 sq. ft. of vent area for every 150 sq. ft. of attic floor, with the vents placed commensurately near, or at, the ridge and the eaves.