rafter vents (baffles)

Attic ventilation demand ridge vents and soffits, which require rafter vents (also called rafter baffles, insulation baffles or, more simply, baffles). Without rafter vents - the channels for air flow - attic ventilation will be less effective or compromised.

Attic Insulation

Baffles ensure a airflow path for air to move into the attic (at the soffits) and out of it through the ridge vent. They can also protect the insulation.

The baffles (rafter vents) are an essential part of most attic and cathedral ceiling insulation systems.

See, for details: Attic insulation

Baffles installation

Baffle installation is simple, and typically done after ceiling insulation.

Just staple the baffles directly to the roof decking, between the rafters (see image from Oak Ridge National Laboratory). Rafter Vents

Rafter vents usually come in 4-foot lengths (1,22 m).

14-1/2 and 22-1/2 inches (4,425 m and 6,8625 m) are standard widths, which should be chosen according to the rafter spacing.

After installing the rafter vents, add also insulation around them (out to their edge).

Types of baffles

Common baffles are cardboard and foam.

Cardboard baffles are inexpensive and easy to cut and to fit, and typically face nailed to the top plate. Their disadvantage is that they are prone to absorb moisture. Baffles

That makes foam baffles a good alternative to cardboard ones. They involve a piece of foam, to be nailed to the roof deck - and ofent another piece working as an end dam, to avoid insulation from flowing out into the venting space (see image, depicting the rafter baffle -in orange -, and considering a soffit dam (in gray) to protect the loose-fill insulation).

The market is now offering new baffles, with new designs. That’s the case of the Accuvent baffles (see image), made from recycled PVC, reducing the limitations of traditional designs…

Improving the attic ventilation with raised top plates

The effectiveness of the attic insulation and its ventilation depend largely on the exact roof design.

Just compare the design depicted in the last image with that of the first image, in this page. The raised top plate (in red, in the last image) is a small detail that allows more insulation at the ceiling and also a better ventilation of the system.