Roof ventilation in North Alabama

Any roof being replaced, homes with unusually high summer cooling bills, and roofs showing heat damage, condensation or early shingle aging from underneath.

Attic heat in this climate is severe. An under-ventilated attic runs far hotter than the outside air, and that heat cooks the shingles from underneath, the side no one can see from the ground.

Two roofs with the same shingles, installed the same week by the same crew, will age differently if one is properly vented and the other is not. Ventilation is the least glamorous part of a roof, and it affects service life more than the choice of shingle.

Ventilation works by moving air, and air needs a way in as well as a way out. Ridge exhaust with blocked or too little soffit intake does very little. The system simply cannot draw.

Mixing exhaust types can make it worse. A ridge vent and a powered gable fan on the same attic often pull air from each other instead of from the soffit. They ventilate a small loop and leave the rest of the attic still.

• Net free area at the intake, meaning the actual open space air can pass through, against what the exhaust needs
• Whether soffit vents are truly open, or have been paneled, painted or insulated over. All three are common.
• Whether insulation is blocking airflow at the eaves, and whether baffles, simple channels that hold it back, are needed
• Whether the existing exhaust types work together or against each other

A properly balanced passive system needs no electricity, has nothing to break, and generally outperforms a fan fighting against too little intake. Fans are sometimes the right answer on a difficult roof shape, but they are not a fix for blocked soffits.

• Shingles curling, blistering or losing granules early, especially on the sunny side
• Unusually high summer cooling bills
• Solid soffit with no vents, or vents caked with paint
• A ridge vent plus gable fans or box vents all on the same roof
• Condensation or a damp, musty attic in cold weather