A rafter vent is a channel used to improve attic ventilation. These foam or plastic channels are installed between the rafters in an attic to create an air space between insulation materials and the rafters. Rafter vents may also be known as insulation baffles because they are generally installed as part of the insulating process.
Installers place a rafter vent into the void between each set of roof rafters. The vent must be placed tight to the edge of the attic wall along the soffit to ensure it will work properly. Snips or utility knives can be used to cut these vents to the desired length, and different widths are available to meet the needs of different framing patterns. Staples or nails are used to hold the vent in place. Once these vents have been installed, blankets or loose-fill insulation can be placed on the attic floor and between the rafters.
The rafter vent allows air to travel freely along the slope of the attic roof. The channel created by each rafter vent provides a clear path between the soffit vents and the gable vents in a standard attic. Without a rafter vent in place, insulation could easily block the soffit vents and prevent fresh air from entering the space.
By helping to maintain adequate airflow within an attic, rafter vents help to reduce problems with ventilation, air quality, and moisture in the home. Providing a path for moisture to escape the attic helps to reduce problems with mildew and mold, which can pose a threat to health and property if left unchecked. Proper ventilation keeps air in the attic from feeling stale, and also helps to improve overall air quality within the home. Finally, sufficient attic ventilation is key to allowing excess heat to escape, which helps to keep energy bills in check.
In an uninsulated attic, there is generally no need to install rafter vents at all. These vents are also unnecessary in homes that rely on a specialty form of attic ventilation instead of traditional soffit vents. If insulation batts or foam board are installed in a carefully controlled manner, and builders are careful to avoid blocking soffit vents, rafter vents may not be needed. In the majority of applications, a rafter vent should only extend just past the edges of the soffit. Continuing these vents all the way to the gable vents is often a waste of money, and does little to improve ventilation.