The Importance of Attic Ventilation

An attic is defined as the unconditioned space between the roof and the ceiling or walls of your home. In most homes with pitched roofs the attic is usually partially or fully accessible. Attics in homes with low sloped roofs may be inaccessible. One thing that is sometimes overlooked is the proper ventilation of an attic space. Signs of inadequate ventilation are rusting nails, excessive heat build-up, and wet or rotted roof sheathing. Adequate attic ventilation may be measured by calculating the ratio of the free area of all vents to the floor area. If a vent has an insect screen its free area should be reduced by one half. The vent free area to floor area ratio should be 1 to 150. If your calculated ratio is less, consider adding ventilation, especially in hot and humid climates like Florida.

If you want your roof to last, you need an attic that “breathes.” The problem is, an estimated nine out of 10 homes don’t have a properly balanced attic ventilation system in place. As a result, the average roof lasts only 10 to 12 years, even though most roofing shingles are made to last 25 years or more. In fact, the number-one reason for early roof failure is deficient ventilation.
What most homeowners don’t grasp is that without proper ventilation, most manufacturers’ shingle warranties are void. That equates to those same nine out of 10 homes may never have had warranty protection on their roofs.

What Happens with Inadequate Ventilation?

Issues caused by inadequate ventilation may not become clearfor years to come, and it can be very difficult to get most installers to come back and correct flaws in the original installation. Inadequate ventilation can result in higher energy costs, structural damage, surplus moisture and ice damming.

Higher Energy Cost

  • Air conditioning and heating systems are overworked.

Structural Damage

  • Plywood decking can come apart.
  • Roof framing can twist or buckle.
  • Vinyl siding outside the home can warp or buckle due to extreme heat in the attic.
  • Shingles overheated from below can be damaged (damage to shingles caused by improper installation is not covered under warranty).

Excess Moisture

  • May create mold and mildew buildup
  • Condensation can induceinsulation to become moisture-soaked and compacted, greatly reducing its efficiency.
  • Paint on interior and exterior walls may bubbleand peel.

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