There’s a lot going on in an attic in terms of airflow, even though no one is usually up there to notice it. Vents at both the bottom and top of the roof allow air to circulate in from the bottom and out at the top, and, ideally, the temperature and moisture levels stay similar to what they are outdoors.
How Attic Airflow Works
Airflow in an attic is based on the principle that hot air rises. Air comes in from the bottom through soffit and gable vents and then exits the top of the roof through ridge and turbine vents. Along the way, it runs along the sheathing on the underside of the roof and dries the moisture that can lead to rot.
Signs of Good Ventilation
The correct amount of attic ventilation is roughly one vent for every 300 square feet. On the top of the roof, turbine vents harness the power of the wind to draw air through the attic. When you go into an attic, it shouldn’t be too hot or too cold compared to the outdoors. If either of these is the case, there is some sort of ventilation issue.
What Happens With Poor Ventilation
If an attic isn’t properly vented, heat and moisture build up inside it. In colder conditions, this trapped heat can melt the snow on the roof, which then flows to the bottom of the roof. Once there, it freezes again and creates ice dams. These obstructions prevent water from flowing off the roof altogether, so it backs up under the shingles and causes rot.
A rule of thumb is that there should be roughly the same number of vents on the bottom of the roof as on the top. When this isn’t the case, the airflow won’t be sufficient to dry out moisture.
Shingles also have a shorter lifespan if the attic is too hot. This can even affect your coverage; some insurance companies won’t pay for a new roof if they see that shingles have worn out before they should have.
Common Ventilation Mistakes
Insulation over soffit vents is one of the main causes of poor ventilation. Insulation placed too close to the edge of an attic floor prevents air from rising up from below, and the attic will quickly overheat.
The attic areas over bathrooms are prone to roof rot because moisture rises up through unsealed areas of the bathroom ceiling after the shower is used. Even when there is proper insulation in an attic, these areas need to be monitored.
Knowing how ventilation works in an attic can help you make sure that your roof lasts as long as possible. It’s a good idea to check all attic vents at least annually to make sure they are clean and unobstructed. When you need roof ventilation services in Etna, ME, contact Home Roofing Solutions.
