How to Prevent Cold Air With Soffit Vent Dampers

Cold air filters in through soffit vents.

Even in cold weather, your home’s attic benefits from air circulation that allows warm humid air to escape through upper roof vents and fresh cool air to filter in beneath the roof. Soffit vents install in the horizontal soffit boards under the roof eaves and most of the time; you won’t notice any difference in indoor temperature. If you have a finished attic, however, the dead space behind the knee walls may become cold due to freezing air coming in from the soffit vents. To reduce the cold air, you can install soffit vents with dampers.

Things You'll Need

• Soffit vents with dampers
• Cordless drill

Instructions

1. Measure the width and length of the existing soffit vents. Standard soffit vents are typically 4, 6 or 8 inches wide and 16 inches long. The roofing contractor determines the size and the number of vents to install by figuring the square feet of floor space in the attic. Purchase the same size vents.

2. Remove the old soffit vents with a drill fitted with a screwdriver bit.

3. Position a new dampered soffit vent in the exact spot where you removed the old vent, turning the louvered vents to face the house. Before attaching the new vent, turn the knob on the face of the vent to see how the damper plate opens and closes.

4. Insert the screws that came with the vent, using the drill and the screwdriver bit. Replace all the old vents in the same manner.

5. Turn the knob or handle, located on the center of the soffit vent to open and close the damper.

Tips & Warnings

• Most soffit vents don’t have dampers because air circulation is vital to the structural integrity of the rafters and the roof decking.

• Damper the vents only when needed, but leave at least one soffit vent slightly open on each side of the house to provide minimal airflow.

• Consider installing insulation behind attic knee walls to offset the cold air from the soffit vents.

• Heat buildup beneath the roof can warp rafters and roof decking and can “scorch” shingles, reducing the life of the roof.

References

• Energy Star.gov: About Attic Ventilation