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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

1.10 Install Self-Sealing Bituminous Membrane in Cold Climates

In colder climates (IECC Climate Zones 5 and higher), install self-sealing bituminous membrane or the equivalent (“ice flashing”) over the sheathing at eaves to provide protection from ice dams. The ice flashing shall extend up the roof plane from the eave to a point at least 2 ft. inside the vertical plane of the exterior wall.

Exception: Climate Zones 1 to 4, as shown in IECC Figure 301.1.

Detailed Illustrations

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Roof drip edge

Roof drip edge

Ice dam protection

Ice dam protection

Why

Self-sealing membranes (sometimes referred to as "peel-and-stick membranes") protect the most vulnerable areas of the roof sheathing from the effects of water, particularly the buildup of ice along the edge of the roof (ice dams). In cold climates, inadequate insulation in the area of the attic directly over and adjacent to the point where the outside wall meets the attic allows the home's heat to warm the attic and roof deck and melt the snow above it on the roof. Conditioned air leaking from living spaces into these same areas can have the same effect. The melted ice and snow will refreeze after draining to the cold eaves, creating icicles and ice dams. As this cycle continues, liquid water can be forced up the roof and under the shingles. Over time, it will rot the sheathing and leak into the attic where it will provide moisture to promote mold growth. Providing adequate insulation that extends over the external walls and air sealing the ceiling between the house and attic are the most important steps in preventing ice dams. Applying the membrane 24 in. inside the wall plane will provide added protection against all but the most extreme ice dams.

How

The membrane used for protection from ice dams should first be applied at the eave and extended up the roof to a point at least 24 in. inside a line projected vertically from the inside surface of the exterior wall. This is the area that needs protection from the repeated thawing and freezing of ice at the eaves. The membrane is a back-up measure of protection; to avoid warming the attic space enough to cause ice dams, air sealing must be done to keep warm house air out of the attic. Proper air sealing is required by EnergyStars' Thermal Enclosure System Rater Checklist.

Refer to the Map of Climate Zones, to determine Climate Zones 5 – 7 and consult code officials when local climate conditions might dictate the need for protection from ice dams.

References/Additional Information

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