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Unwrapping the Exterior: Weather Resistant Barriers

Weather Resistant Barriers –  or WRBs  – are a crucial element of construction and one of the biggest factors contributing to a building’s energy efficiency. Commonly referred to as building wrap, WRBs have been a widely-used method for protection against moisture since the 1970s, evolving into air moisture barriers in order to control air and vapor flow. Building codes require a skin on every building, and WRBs are the skin.

WRBs are designed to protect the walls of a structure from air infiltration and moisture intrusion. They are designed to block air from the outside while allowing the walls to effectively “breathe,” ensuring a building retains its heat and air while remaining healthy and comfortable.

As code changes drive increases in energy efficiency, the air and vapor permeability of a wall system becomes an important element to manage. The technology behind these barriers has improved as the demand for climate-controlled buildings has increased. To learn more about building wrap and how it can impact the energy efficiency of a building, let’s take a look at a few products from Tremco, a leading manufacturer of construction products and waterproofing, to help illustrate some key concepts.

Products like these, along other types of air vapor barriers, can be found at various L&W Supply branches.

ExoAir from Tremco

A building under construction
with an air membrane installed

Tremco EXOAIR 230 is a permeable air barrier membrane designed to be rolled or sprayed onto exterior above-grade wall assemblies. It is typically applied to exterior sheathing panels, concrete block, or wood substrates as and air a moisture barrier material. This is the same product used as the air barrier on Securock EXOAIR430 (the 430 numbering is a reference to the fact that the product is factory installed on the Securock panels).

  • Installation – The ability to roller or spray apply material accelerates the installation process, combining both the substrate and AMB in one installation
  • Performance – Vapor-permeable system providing greater flexibility in placement in wall systems
  • Durability – Formulated for UV resistance, allowing the membrane to be exposed longer during construction process

Tremco Dymonic 100 is a high-performance and high-movement polyurethane sealant, primarily used as a fluid-applied flashing material in rough opening perimeters for windows, doors, and other openings. It is designed for sealing up board joints, corners, and maintaining transitions and reducing airflow. Other applications include expansion and control joints, precast concrete panel joints, perimeter caulking, and vinyl siding.

  • Installation – Unique ability to adhere to damp or green concrete and suitable for water immersion, allowing for increased versatility
  • Performance– Comes with a skin time of 2 hour with a tack-free time of 6 to 8 hours to reduce dirt attraction
  • Durability – Designed not to crack, craze or yellow under exposure, with a movement capability of +100/-50% in typical field conditions
Tremco Logo

Tremco are among the many Exteriors
products found at L&W Supply

When evaluating the right sealant or building wrap for a project, it is important to determine the potential performance of the exterior system based on similar criteria that we have used here. This is where it helps to have the knowledge of a sales representative to guide your decision-making. Not only is it important to determine how effective your WRB products are, but it is also crucial to learn how they interact with the other products in the rest of the wall system.

Unwrapping the Exterior

Just as no two projects are the same, no two wall systems are the same either. There are many other products contained within the exterior of a building, each with their own important function. Check back on our blog for more content related to exteriors, where we continue to

For questions or inquiries on the best use of weather resistant barriers, air moisture barriers, or other exterior products, please contact your local L&W Supply branch. Our knowledgeable associates are available to discuss the best product and system for your specific project. Tremco and Dryvit products are currently stocked at many L&W Supply branches, along with many other products from top manufacturers. Use our location finder to learn more.