Asphalt Shingle Roofing Ventilation Needs


Proper attic ventilation systems allows a continual flow of outside air through the entire attic in your home while protecting the efficiency of the insulation and helping to lower temperatures in the living area. House ventilation is perhaps the most misunderstood area of roofing. You need ventilation for the life of roof. Used to long time ago, homes would ventilate themselves, heat and moisture used to escape through old windows, doors, and even right through the walls. New materials today seal in buildings.

Using insulation, new high-tech materials, with high-tech installation methods, seal off a building. Vapor barriers, non-breathing materials, and further seal off the buildings. Vinyl siding with insulation traps moisture and hest in structure. High-tech windows whether vinyl or wood, modern windows let very little air in or out of a structure.

Ventilation is used to reduce heat, excessive attic heat can do damage to the roof. Attics can heat up to 165F or more. This heat radiates into your home, overhead attics mean overheated homes. Overheated homes cost homeowners thousands of dollars in air conditioning. Attic heat can damage wood frames making attics subject to structural woodwork to warping and cracking. Excess heat can also make a structure peel the exterior paints.

Overheated roof decks can reach over 170F. Heat can reduce shingle life; overheated roof decks can actually “cook” roofing materials, reducing their effectiveness. This can affect the shingle’s performance. Most major shingle manufacturers including GAF-Elk require ventilation meeting FHA minimum requirements.

Moisture builds up in all structures. Moisture sources include showers, baths, and washing. Cooking and cleaning, not to mention heating and cooling systems. This moisture can turn into vapor; some gets locked into the building. Some moisture can travel through the ceilings, once airborne; it will migrate through ceilings using natural convection. In most structures, this moisture stops at the roof deck, condenses on the deck, changes from vapor to water then settles on the interior of the deck and on cold attic surfaces which then drips onto dry insulation.

Trapped moisture will damage woodwork in attics. Plywood will delaminate and rot away. OSB will expand and rot. Structural frames will warp and rot. Excess moisture will drip down onto insulation and reduce its effectiveness. Attic moisture can lead to mold and mildew problems throughout the entire structure.

Every home should have adequate moisture ventilation in the attic and roofing system. This will keep the roof in good shape and keep your family safe also.


Source by Joseph Vann Hamby Sr.