The Importance of Insulation Baffles

Overview

• In many homes, soffit vents under the eaves allow fresh air into the attic. This causes the hot air in the attic to rise, where it escapes through ridge or gable vents higher on the roof. If you install insulation without using baffles, the insulation can cover the soffit vents, which prevents fresh air from entering. Insulation baffles installed where the roof meets the floor of the attic provide a permanent path for air to flow from the soffit vents to the ridge or gables. These baffles resembles a flat channel attached to the attic sheathing. Attic insulation rests against the bottom of this flat channel to insulate the attic without blocking vents.

Function

• Insulation baffles serve three basic functions. First, they serve as a barrier between the insulation and soffits to prevent blockages. Second, they allow installers to place insulation over the top plate of the wall framing without also covering the soffit vents, which allows for better thermal resistance for the living spaces below. Finally, insulation baffles prevent wind washing, which occurs when strong winds blowing through the soffit vents blow insulation away from the edges of the attic. This not only leaves the top plates uncovered and reduces energy efficiency, but can also drive water into the attic.

Benefits

• By leaving the soffit vents free to do their job, insulation baffles serve as an important part of an attic ventilation system. Proper ventilation keeps heat from building up during the summer to keep the home more comfortable, and prevents problems with moisture year-round. By preventing wind wash and allowing installers to insulate all the way to the top plate, baffles also reduce the risk of ice buildup along the eaves in the winter, a phenomenon known as ice damming.

Types

• The most economical baffles are made from cardboard, and resemble standard pizza boxes in terms of texture and thickness. Although cardboard baffles are cheap, they are also vulnerable to moisture, mold and mildew. Foam baffles cost slightly more, but offer greater resistance to moisture. High-end baffles are often made from rigid plastic and composites.

Installation

• Install insulation baffles in between the rafters where the ceiling meets the floor in your attic. Staple them directly to the roof decking or sheathing, with staples placed every 8 inches on center along both the outside edges and the center flange. When you're ready to install your insulation, butt the insulation up against the face of the baffle so that it covers the top plate of the roof framing.