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To reduce the risk of condensation on the interior of the roof sheathing in cold weather, the ratio of exterior (above-deck) insulation must be increased as a percent of total attic insulation as outside temperature decreases

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R-5 XPS rigid foam exterior sheathing provides an air seal, moisture barrier, and additional insulation value.

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This farmhouse was retrofit by removing the existing siding and adding taped insulated sheathing and battens before installing new siding

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Stucco is installed over rigid insulation, which is installed over a drainage plane consisting of a drainage gap and building wrap layer over the sheathing

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Condensation Control for Walls in Cold Weather

Guide

Guide describing ways to construct wall assemblies in cold climates to minimize the likelihood of condensation formation inside the walls.

Moisture Management in Residential Construction Series - Building Enclosure: Exterior Wall Overview

Video

Video from Home Innovation Research Labs giving an overview of moisture problems common to exterior walls and how to mitigate these problems with proper framing, flashing, sheathing, cladding, and insulation.

They All Laughed, BSI-026

Reference

Article describing the evolution of the IRC to permit class 3 vapor retarders (latex paint) in walls coupled with exterior continuous insulation to allow drying and reduce condensation risk.

Mastic Home Exteriors Installation Guide

Reference

Siding installation guide for Ply Gem Siding Group products.

Waverly Home Addition | Exterior Cladding Details

Video

Video describing the exterior cladding details of a residential home addition project.

The builder installed 1.5 inches of soy-based spray foam on the outside of the walls over the OSB sheathing, then kept a ¾ inch gap between the foam and the brick veneer siding to allow moisture vapor from the bricks to dissipate.

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Right: All joints in the rigid foam are taped to keep stucco out of joints for even drying. Mesh tape (shown here) is used with expanded polystyrene (EPS); acrylic sheathing tape or self-adhered membrane is used with XPS

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Building America Building Science Advisor

Reference

Web based tool providing decision-making guidance for selecting wall assembly components.

When condensation forms on the interior side of wall sheathing and is not able to dry out, it can lead to mold growth and rotting of wall sheathing and framing

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Moisture Control for Residential Buildings

Reference

Report providing extensive guidance on controlling moisture in building envelopes through proper selection and installation on air, water, thermal, and vapor barriers.