Install Rafter Baffles in Your Attic

Rafter baffles are the unseen infrastructure that keeps your attic breathing properly. Without them, blown-in insulation creeps toward the eaves, blocks your soffit vents, and turns your attic into a moisture trap that rots sheathing and grows mold. The fix takes an afternoon and costs less than fifty dollars, but it prevents thousands in damage and makes your insulation actually work. Most attics need baffles in every rafter bay where insulation meets the roof deck. The job is straightforward but uncomfortable—you'll be working in tight spaces near the eave edge where headroom disappears. The goal is simple: create a permanent air channel from each soffit vent up past the insulation, allowing cool air to enter at the eaves and exit at the ridge. Done right, you'll never think about them again. Done wrong, you'll discover the problem when you see water stains on your ceiling.

1. Clear the eave edges and measure spacing. Pull back existing insulation from the first six feet of each rafter bay, exposing the top plates and roof deck. You need to see bare wood where baffles will mount. Measure the width between rafters—most are 14.5 or 22.5 inches on center. Count how many bays need baffles by checking which ones have soffit vents below.
2. Cut baffles to length. Each baffle runs from the soffit vent opening up the roof deck about 48 inches—past where insulation will sit. Cut rigid foam baffles with a utility knife or use pre-cut cardboard versions. The baffle should extend at least 12 inches beyond the highest point your insulation will reach.
3. Position first baffle at soffit opening. Slide the baffle into the rafter bay with the bottom edge resting on the top plate, directly above the soffit vent. The baffle should sit snug against the roof deck, creating a channel between the sheathing and the insulation below. Check that air can flow from the soffit vent into the channel.
4. Staple baffles to rafters. Use a staple gun to secure the baffle edges to both rafters every 8-10 inches. Start at the bottom and work up. The baffle should be rigid against the roof deck with no gaps where insulation could slip behind it. Don't overdrive staples through foam baffles.
5. Seal edges with expanding foam. Run a small bead of low-expansion foam along both sides where the baffle meets the rafters. This prevents insulation from sneaking around the edges and blocking airflow. Let foam cure for 15 minutes before moving on.
6. Repeat for all remaining bays. Install baffles in every rafter bay that has a soffit vent below. Keep your pattern consistent—same length, same staple spacing. Work methodically across the attic rather than jumping around. Most attics need 20-40 baffles total.
7. Verify airflow through each bay. From below, hold your hand near each soffit vent and feel for airflow if it's a breezy day, or shine a flashlight up from outside to verify the channel is clear. From the attic, look down each baffle to confirm nothing is blocking the path.
8. Replace insulation against baffles. Pull the insulation back into place, butting it against the bottom edge of each baffle but not compressing it into the channel. The baffle creates a dam that keeps insulation back while air flows above it. Add more insulation if needed to reach recommended R-value for your climate.