To better understand this process the following points will be addressed:
1. Common Ventilation Types
2. Breath In
3. Breath out
4. Baffle Vents
Ventilation is the continuous flow of air thru your attic space. The condition of your attic will determine everything from your monthly power bill to the lifespan of your roof. Yet strangely only somewhere between 10%-30% of roofs are ventilated correctly. Leaving many people with the high risk factors that they likely don’t realize is lurking right above their very heads.
1. Common Ventilation Types
There are many different ways to go about ventilating your attic. Some of the most common include Ridge Vents, Power Vents, Gable Vents, Turbine Vents and Box Vents.
The way these vents work can vary slightly. Turbine and Box Vents work by relying on wind to operate them, drawing hot air up out of the attic. But these mechanisms can be less reliable on days when wind is scarce. Power Vents are on the other side of the spectrum. They have thermostats built into them that allows them to kick on when the temperature in the attic reaches a certain point. In the middle are Ridge and Gable Vents. Ridge and Gable vents both rely on the idea that the house also has soffit vents. The cold air comes in thru the lower soffit area and as hot air rises it exits out the Ridge or Gable vents.
2. Breath In
Airflow in the Soffit Vents and Out the Ridge Caps
Ventilation is not just the removal of unwanted hot or cold air from your attic. Ventilation also includes the intake of new fresh air too. Ideally this process should be comprised of 50% intake on air and 50% exhaust. Air intake for your home takes place at a lower level. Primarily thru the Soffit vents located at the eves of your home, but some thru the gable area on the side of your home as well. The first thing you want to look for is that your home has some sort of intake area to bring the fresh air in. Without an intake area to push existing air around the appropriate amount of air will not exit back out which leaves air stagnant in the attic. Stagnant air can cause several negative factors to occur.
Both stagnant cold air and hot air come with negative consequences. In the cold of winter air that is left in the attic will accumulate moisture build up. This moisture will condensate on the boards in the attic eventually causing rott and destruction to the structure of the roof. While in the heat of summer hot air building up in the attic acts like an oven for your roof. It “bakes” the shingles on the roof causing blistering and peeling of the shingles.
Result of Heat in Attic
Continual airflow in the attic is the key to protecting against these previously mentioned issues. If your house does not have soffits to assist in keeping the air flowing in and up so it can exit out the Ridge or Gable vents you are certainly at risk for some serious issues.
3. Breath Out
Roof Cut for Roof Vent
The key to air exiting the roof is not always as simple as popping a vent on and being done with it. To start with, it is necessary to cut the wood decking back by a minimum of 1” on each side from the center ridge board. This is necessary not only from the aesthetic perspective but also so that the seal against the ridge vent is straight on and does not let water in. The final item to go on top is the Ridge Cap. The Ridge Cap is critical because it protects the Ridge Vent. Without this overtop the ridge vent would be open for water to go into. This piece instead acts as a protective cover over top of the open ridge. The ridge vent should be installed across the length of the roof in order to provide adequate breathing of the roof across the whole span of the attic.
4. Baffling Vents
Foam Attic Baffling
Baffles are not found in all residential homes, but they serve an important purpose in the homes that require them. Baffles are typically located between the rafters and roof sheathing. They are designed to keep blown insulation from crowding the Soffit Vents. If the Soffit Vents are blocked by insulation proper air flow cannot take place. To prevent this from happening contractors will install the Baffles to provide a clear pathway past the insulation for airflow to take. Baffles are fairly straight forward mechanisms that are easy to install.
For assistance in calculating the proper amount of attic ventilation necessary for your home please visit GAF’s website for a ventilation calculator.
Click Image for Ventilation Calculator