Quick answer
An attic baffle is a simple channel, made of foam, plastic or cardboard, fitted between the rafters at the eaves. It keeps insulation from blocking your soffit vents, so outside air can flow up under the roof. Yes, most attics with soffit vents need them, especially before adding more insulation.
What baffles do
- Keep the soffit vents open so fresh air can enter the attic.
- Let moist air escape through the roof or ridge vents.
- Keep the roof deck cold and dry, which helps prevent mold, frost and ice dams.
- Let insulation go full depth right out to the edge of the wall.
Signs your attic needs baffles
- You can’t see daylight at the soffits from inside the attic
- Insulation is piled into the eaves
- Frost or mold on the roof boards near the edges
- Ice dams or big icicles in winter
- You are about to add insulation (this is the time to install them)
Types of attic baffles
| Type | Good for | Watch out for |
|---|---|---|
| Foam (polystyrene) | Most common, easy to fit | Can crack if handled roughly |
| Plastic | Durable, moisture-resistant | Must match rafter spacing |
| Cardboard | Low cost | Can sag if it gets damp |
How they are installed
One baffle goes in each rafter space that has a soffit vent below it. It is stapled to the underside of the roof deck, running from the top of the wall up past where the insulation will end. Many installers also fit a block at the bottom so blown-in insulation can’t spill into the soffit. The work is done from inside the attic, usually right before the new insulation goes in.
Do it at the same time as insulation
Baffles are much easier to install before new insulation is blown in. Adding them later means digging the insulation back out at the eaves.
Do you need baffles with blown-in insulation?
Yes, in almost every case. Blown-in insulation flows like snow and easily drifts into the eaves and covers the soffit vents. Baffles hold it back and keep the air channel open.
Frequently asked questions
How much do attic baffles cost?
They are an inexpensive part of an insulation job. The material is low cost, and most of the price is labour. They are usually priced into the insulation quote.
Can too much ventilation be a problem?
Balanced ventilation is the goal: roughly as much air coming in at the soffits as going out at the top. A good inspection checks both.
My house has no soffit vents. Do I need baffles?
Not at the eaves. But your attic still needs a way to ventilate, and that should be checked before adding insulation.
Want the bigger picture? Read how much attic insulation you need and what causes attic mold.
Is your attic breathing properly?
Our free inspection checks soffits, baffles and ventilation, not just insulation depth.