Moisture management in remodeling projects

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Remodeling a house is a multi-faceted project, and an important part of remodeling is to protect it against air and water infiltration.

December 28, 2011

Remodeling a house is a multi-faceted project, and an important part of remodeling is to protect it against air and water infiltration.

A well-constructed building envelope, with a continuous air and moisture barrier, drainage plane and a layer of continuous insulation provides both moisture control and the added benefit of energy savings.

Different climates require different combinations of wall components for ideal protection. A system with air barrier protection, drainage cavity and continuous insulation aligns with the latest in building science and the new regulations that support both green building and moisture protection across all climate zones — from cold to hot and humid. A system has all parts working together.

Fluid-applied air barrier

A fluid-applied waterproof air barrier membrane bonds directly to sheathing or other substrates to resist air and water penetration. It protects against the damaging effects of incidental water and air infiltration that can enter and damage wall components, and one with vapor diffusion aids in preventing condensed water vapor from getting trapped inside walls.

According to Energy Star, sealing the building enclosure is one of the most cost effective ways to increase the energy efficiency of a building. Installing an air barrier system delivers significant energy savings in both hot and cold climates, and helps improve indoor air quality. A fluid applied membrane is an air barrier and wall moisture barrier that is structural and continuous, so it won’t rip or tear away from the sheathing like sheet house wraps or building wraps.

Continuous insulation

Continuous insulation is like wrapping the building exterior in a thermal blanket, enhancing energy efficiency and minimizing thermal bridging, and significantly improving the effective R-value of the wall assembly.

The insulation benefits of EIFS have long been recognized and with recent energy code changes EIFS is becoming an increasingly attractive and economical approach to providing continuous insulation. The provision of continuous insulation requires that the exterior cladding be cantilevered out from the wall structure by the thickness of the insulation. This cantilevering of loads can present structural challenges resulting in increased structural costs. This can be particularly challenging for retrofit projects where the original walls were not designed to accommodate these additional loads. The light weight of EIFS makes it a very attractive approach for the provision of continuous insulation for both new construction and for retrofit applications.

Rainscreen technology

A drainage system or rainscreen is an assembly where the cladding or exterior weather-facing surface of an exterior wall stands off from the moisture-resistant surface of the structural backup wall. The rainscreen (or drainscreen) is the first interruption between conditions that exist on the outside of a walled building and conditions that are required on the inside of a walled building. In a rainscreen the air gap allows the circulation of air behind the cladding. This helps remove condensation and incidental water intrusion. The air barrier limits air infiltration and exfiltration through the assembly at the sheathing plane.

A drainage cavity allows water that reaches the back of the cladding to drain to the outside and also creates an air gap that allows air movement behind the cladding to aid in removing moisture, while providing a capillary break.

Other ways of keeping the walls dry

Claddings have different capabilities when it comes to protecting against moisture intrusion and energy loss. Keeping walls dry is a function of many factors – building height, orientation and severity of exposure to wind and rain, and building design details. Particularly important is the incorporation of flashings at critical locations — at the base of the wall, floor lines, roof/wall intersections, lower to higher wall intersections, beneath sills and copings, and at parapets — to direct water to the exterior, not into the wall assembly. The quality of components such as windows, doors, and sealants, and the installation of all components to prevent water intrusion behind the cladding, are also critical for the ultimate performance and waterproofing integrity of the building enclosure.

Lisa Petsko is a product manager at Sto Corp. She is a member of the Air Barrier Association of America. Petsko graduated from Virginia Tech University and has an MBA from Kennesaw State University in Georgia.

 

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