What Are Baffles in a Vaulted Roof?

Insulation Baffles

• Baffles, also called vent chutes or rafter vents, are insulation devices that create a gap between attic insulation and roof sheathing. Baffles assist in the free flow of air from the soffit vents into the attic. They prevent insulation from covering the soffit vents so that the air flows from the soffit vents to the ridge vents.

How Insulation Baffles Work

• Baffles fit below the roof structure providing a corridor for the air that rises from thermal convection that then escapes through the ridge vents. When soffit vents are blocked by insulation, this air flow does not occur. Baffles are installed that hold insulation out of the way of venting currents. Baffles are usually 16- to 24-inches wide and fit easily between rafters.

Types of Insulation Baffles

• Insulation baffles are often made of cardboard or foam, though more recent types are plastic, generally recycled polyvinyl chloride, according to the BuildIQ Web site. A cardboard insulation baffle resembles a pizza box. It is very flexible and folds to fit against the trusses, as needed. It absorbs moisture and can be a food source for mold growth. Foam baffles are formed pieces nailed to the roof deck. Although they do not absorb moisture, they can become brittle and break. PVC baffles are both flexible and mold-resistant, but may are expensive than other baffles.

Baffles in Vaulted Ceilings

• Vaulted, or cathedral ceilings, may have special problems with ventilation because the ceiling framing and roof framing are the same, according to the Check This House Web site. In this type structure, no accessible attic area exists, only a narrow truss space that may be partially filled with insulation. The lack of air flow causes moisture stains on the ceiling surface or condensation dripping from lighting fixtures. Fitting baffles into the area holds insulation in place, allowing air flow through this narrow available space.