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Huntsman Announces UL Certification for W-Wall Assembly

Certification allows for easy conversion from other fire-rated wall design options to high-performance W-Wall

Huntsman Building Solutions

The W-Wall Assembly with open cell spray foam applied.

Huntsman Building Solutions (HBS), a global leader in high performance, sustainable building envelope solutions, today announced UL certification has been obtained for W-Wall^™, the fire-rated load-bearing assembly utilized as a wall solution between attached multifamily and townhome units. The newly certified W-Wall assembly leverages the benefits of OC NO-MIX open cell spray polyurethane foam insulation and performs as a tightly sealed fire partition wall.

The W-Wall assembly design fulfills three key functions including providing an air seal that solves blower door issues, meeting two-hour fire-rated load-bearing wall requirements, and offering sound attenuation (i.e., noise reduction) between residential units.

“Builders and architects are commonly challenged with finding a reliable fire wall that successfully fulfills all of these roles and that can also be installed at a reasonable price,” says Douglas Brady, President of Huntsman Building Solutions. “In essence, this certification is ideal because it allows them to seamlessly transition away from less attractive wall design alternatives to the W-Wall assembly system, which is ultimately the higher value option.”

W-Wall’s assembly incorporates a series of materials in addition to Huntsman Building Solutions’ OC NO-MIX open cell spray foam insulation. These materials include: wall sheathing consisting of two layers of 5/8” Type X Gypsum wallboard on each side of the assembly; walls constructed with 2x4 studs at 16” on-center (no need for 8” off-set); sheathing secured with screws, and the finished layers covered with tape and joint compound; inside wall leaf filled with 3.5” of Huntsman Building Solutions open cell spray foam insulation; and a 1” minimum air gap between the two wall leafs. The overall assembly is 1” thinner than the typical shaft wall.

W-Wall is compatible with most common building materials and other air barrier auxiliary products. Additionally, with fewer products to install, fewer workers are needed, construction speed is meaningfully enhanced, and cost savings are achievable.

“Huntsman Building Solutions also offers builders using W-Wall custom design assistance, engineering support, and access to an approved nationwide installer network,” says Paul Warren, Building Science and Engineering Manager with Huntsman Building Solutions.

In addition to its UL certification, W-Wall has successfully passed ASTM E119 as a two-hour load-bearing assembly and ASTM E90 for Sound Transmission Class (STC) in accordance with International Building Code (IBC) requirements. Additionally, the OC NO-MIX included in W-Wall’s UL certification is also code compliant as confirmed in Code Compliant Research Report (CCRR) 1123 and is Greenguard Gold certified, indicating low-VOC emissions and improved indoor air quality.

To view information on W-Wall, visit https://huntsmanbuildingsolutions.com/en-US/sites/en_us/files/2026-01/21.00269-HBS_W-Wall_US_EN_Bifold-V7-DIGITAL.pdf. Explore Huntsman Building Solutions’ full range of building envelope solutions at www.huntsmanbuildingsolutions.com.