Methods to Baffle Soffit Vents

Basic Installation Methods

• Soffit baffles are metal plates with raised ridges along their sides that are installed in the interior of your attic where the exterior walls meet the rafters. Each baffle is installed on the underside of your roof across from the vents in the soffit. These vents are attached to the underside of the roof with staples. Each baffle is mounted between the rafters so that the middle of the baffle is above the top plate of the exterior wall. If your attic has loose-fill insulation you will need to install an insulation dam to prevent insulation from blocking the soffit vent. This dam will also prevent strong winds from blowing the insulation away from the outside walls and prevent the insulation from compressing.

Soffit Dams

• Soffit dams are vertical pieces of rigid material, either cardboard or plywood, that separate the insulation from the area above the soffit vent. A properly installed soffit dam is attached to the top of the wall below the baffle on the outside edge of the wall and extends to the underside of the soffit baffle. This prevents air and moisture from the soffit vent from infiltrating the interior of your walls and allows the insulation in your attic to cover the top plate of the wall.

Tight Spaces

• Roofs often have limited space near the eaves that makes it difficult to install enough insulation to adequately protect your home. The open space required for soffit vents can further reduce the area available for insulation, making your home less energy efficient and susceptible to ice dams during the winter. To prevent this problem, you can install a second top plate above the insulation behind the soffit dam. Connect this plate to the top of each soffit dam and lay it on top of the adjacent insulation to hold it in place. Installing this plate will provide an additional air barrier and keep the insulation in place without compressing it so that it does not interfere with the soffit baffle above.

Considerations

• Baffles are intended to ventilate the attic without restricting the depth of the insulation underneath the eaves of your roof. Compressing the insulation beneath the baffles will decrease its effectiveness. Installing insulation dams will allow you to add insulation at the recommended depth without compressing it. Although materials, such as cardboard and plywood, can make effective insulation dams, they are susceptible to damage from moisture coming through the soffit vent. Installing plastic sheeting over the insulation dam will provide a moisture barrier that will help prevent damage to the dam.