When attic ventilation is properly sized and installed for the home, it works just as effectively moving air through the attic in the summer as it does in the winter. Moving air through the attic helps to relieve heat buildup in the summer which can help to save on energy costs and extend the life of the roof. In the winter, proper ventilation helps to relieve the home of excess humidity and escaping heat. Air flow is critical in preventing condensation (moisture collecting on cold attic surfaces) from forming. Left unchecked, condensation can lead to wood rot, mold growth and a shortened lifespan for your roof.
The idea that air should enter from below the eaves and exhaust at the roof's peak is not a new idea in ventilation, but it is often not achieved. Soffit vents are sometimes added to increase air flow. But merely cutting holes in the soffit does not necessarily mean air flow will be increased. With the recommended attic insulation R value (measure of thermal resistance) of R-44 in the (Mid-West) climate, insulation can be built up to the point that there is no gap for the air to flow through at the eaves. To prevent this issue baffles should be used. As can be seen in the above diagram, baffles were added to keep the insulation from blocking air flow. Baffles are typically made of plastic or styrofoam and are low cost. If not installed when the home was constructed they can be installed from inside the attic. They should be of the same width as the space between the roof rafters and attached to the bottom side of the roof decking. Keeping the air flowing in your home's attic year round will help you to save energy and extend the life of your roof. By: Chip Starkey