BW Universal System™

The BW Universal System is a horizontal insulated metal backup wall panel made by Metl-Span. It belongs to the Lock & Groove system and is a single component that serves as an air, water, thermal and vapor barrier behind an exterior cladding. It is used in commercial and industrial building envelopes in the United States.

The panel is installed horizontally behind many types of rainscreen wall systems, from single skin and modular metal panels to brick, ACM panels and others. It spans up to 24 in. on center.

The panel is offered in two coverage widths and two thicknesses.

• Width: 32 in. or 36 in. The 32 in. width is primarily for brick application.
• Thickness: 2 in. or 3 in.
• Length: 12'-0" or 20'-0", installed horizontally

The exterior face has no profile and is unembossed. The interior face has a shallow planked profile, nominally 3/64 in. deep, also unembossed.

Both faces are AZ-50 aluminum-zinc coated steel in 29 gauge with an epoxy primer finish. The core is foamed-in-place polyisocyanurate.

Adjacent panels join with a tongue-and-groove joint that is fastened concealed from the face side.

The core has a k-factor of 0.119 BTU·in/hr·ft²·°F at a 35°F mean core temperature, measured to ASTM C518. U-factors and R-values for a 36 in. panel width at 35°F are based on ASTM C1363.

• 2 in. thickness: U-factor 0.062 BTU/h·ft²·°F, R-value 16.7 h·ft²·°F/BTU
• 3 in. thickness: U-factor 0.041 BTU/h·ft²·°F, R-value 25.1 h·ft²·°F/BTU

• ASTM E84: flame spread under 25, smoke developed under 450
• NFPA 259: potential heat of the foam plastic insulation measured for the assembly tested to NFPA 285
• NFPA 285-19: a representative mockup was tested; the assembly requires one layer of 5/8 in. Type X gypsum board on the interior side of the steel framing of the panels
• ASTM E72: structural strength tested, with results given in load/span tables
• ASTM E2357: maximum air infiltration rate of 0.002 cfm/sq. ft. at a static air pressure difference of 1.57 psf
• ASTM E331: no uncontrolled leakage at a static pressure of 15 psf for 15 minutes, and none at a differential pressure of 6.24 psf for 2 hours, the pressure and duration used in International Building Code Chapter 14

The system selection matrix pairs exterior rainscreen types with attachment components. The rainscreen types are horizontal profile panels, vertical profile panels, brick, terra cotta, ACM panels, honeycomb panels, stucco and perforated panels. The attachment components are the BWUH rail, the BWUV rail, brick ties and panel clips. The ACM and honeycomb entries are marked separately for horizontal and vertical use.

The BW Stretch System is the companion vertical backup wall panel in the same range. It spans up to 6 ft. on center and uses G-90 galvanized steel faces, where the BW Universal System uses AZ-50 coated steel.

Drawings for the horizontal system cover horizontal panel joint clips, horizontal and vertical rainscreen rails, and masonry panel joint clips. They show base, header, corners, jambs, sills, parapets, endwalls, vertical joints and deflection conditions. The V6 X-Span Clip is listed as a separate detail.

The horizontal system's load span tables follow Allowable Stress Design (ASD), and a US BW Universal load chart is published. ASCE 7-10 (LRFD) loads are converted using the combinations in section 2.4.1 of ASCE 7-10. The guide specification is Section 074217, Insulated Core Metal Wall Backup Panel System.