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Indoor airPLUS

Technical Guidance to the Indoor airPLUS Construction Specifications

1. Moisture Control

Sections 1.7 - 1.10: Water-Managed Roof Assemblies

Best Practice: Wind Baffles - Attic Insulation

Install wind baffles or another form of air barrier in the eave bays of roof assemblies that contain soffit vents to prevent wind from blowing through fibrous insulating materials at the eaves.

Detailed Illustrations: Best Practice Techniques

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Best Practice: Wind Baffles/Rafter Chute

Wind Baffles/Rafter Chute

Best Practice: Soffit Venting Profile

Soffit Venting Profile

Why

Wind baffles (venting chutes, rafter vents) are recommended for traditional vented attics, (i.e., a pitched roof and the ceiling assembly acting as the thermal and air barrier). For effective attic ventilation, air needs to flow freely from the soffit vents and exit at the ridge vents. While these baffles allow loose-fill insulation blown into the attic to fully cover the top plates of the outside walls (thus providing a complete thermal barrier between the attic and the living spaces below), they also prevent the insulation material from falling into the soffits and blocking the vents.

The baffles perform another function. Strong winds blowing up through the soffit vents can blow the insulation away from the wall plates and outer-most areas of the attic. Cold air entering the attic can then lower the temperature of the gypsum-board ceiling below. If the temperature of the gypsum inside the room below the attic drops below the dew point of the indoor air, water will condense onto the drywall and mold will grow.

How

Install baffle materials - such as plywood, oriented strand board, cardboard, foam board, or polyvinyl chloride - in ceiling joist bays and their matching roof-rafter bays so the ceiling insulation covers the top plates of the outside walls, yet there is space for air to flow unimpeded from soffit vents into the attic.

Attic insulation should always extend over the exterior wall plates; if this is not done in cold climates, air from the living space can warm the sheathing at the eaves and help form ice dams on the roof at the eaves, causing water leaks. See Specification 1.10.

References/Additional Information

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