Benefits of Specifying Complete Masonry Veneer Wall Systems – Part 5
This is part five of a seven-part series of blog entries about the benefits of specifying and building with manufacturer-tested and warrantied wall systems compared to specifying individual components. Benefits include a much faster design and specification process, proven component compatibility, faster component installation and better performance, plus the peace of mind that comes from knowing all components are proven compatible and will perform as specified. Part five provides a look at sealants and an introduction to insulation.
Sealants must be compatible with all materials to which they are applied and must also be function-specific. For example, while butyl sealants are perfect for sealing overlapping materials such as flashing membrane joints because they are extremely long-lasting and aggressively adhesive, they must never be used in vertical butt joints because butyl never ‘sets’ and will ooze out of the joint. Butyl also remains ‘tacky’ throughout its lifetime, so it is not paintable, and should not be used where it is exposed and visible because it has the potential to hold dirt and debris. (The specific sealant will be dependent on the materials specified for each project. For assemblies like the one with which the authors are most familiar, a silyl terminated polymer [STP] works well due to its moisture-cure properties, color availability, and flexibility while still being compatible with any incidental asphaltic-based products in surrounding areas. Butyl will also work with many of the system’s installation procedures, including on the brick ledge, at panel overlaps, and at points where membranes overlap corners and end dams, and on top of the termination bar. Other sealant types, such as modified polyether, may also work well, but their effectiveness and compatibility can be material-dependent. A designer should always check with the manufacturer of the sealant they want to specify to ensure the chosen sealant is compatible with the other components.)
The wrong fasteners and washers can pull out and allow air and moisture infiltration. These components should be specified.
Depending on the design, one to three types of insulation may be needed in complete masonry veneer wall systems.
Framed wall insulation
If the structural backup wall is framed wood or steel, then insulation can be installed between the studs. It can be fiberglass, mineral wool blankets or batts, or sprayed polyurethane foam (SPF). Which to specify depends on the needed performance and the jobsite conditions. It is important to keep in mind all framing members—but steel studs in particular—act as thermal bridges between the inside and outside of the building, and will reduce the framing insulation’s effectiveness by up to 50 percent. This is one of the reasons why energy codes such as International Energy Conservation Code (IECC), American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1, Energy Standard for Buildings Except Low-rise Residential Buildings, and ASHRAE 189.1, Standard for the Design of High-performance Green Buildings, prescribe continuous insulation over the studs as well as inside the cavity.
Be sure to come back for part six to learn more about insulation, including continuous and fire-safing insulation.