Green Build & Design recently published an article on what modern architects need to know about firewalls and how the SANCTUARY Two-Hour Firewall is uniquely positioned to meet multifamily construction requirements. Check out an excerpt of the article below and read the full version here.

Everything Architects Need to Know about Modern Firewalls

When a firewall fails inspection, gaps in insulation are often to blame. Then the contractor has to return to the building and repair the insulation, tacking on additional time and cost.

Greenfiber’s SANCTUARY Two-Hour Firewall, a UL-certified assembly filled with Greenfiber FRM insulation, eliminates the gaps in insulation that can lead to inspection failure. Isac Torres, owner of Battle Born, is a contractor who installed the Greenfiber SANCTUARY product in a Las Vegas townhome project—a net zero-ready development in Las Vegas. For the past six years Torres says Battle Born has been using the SANCTUARY product because of its sound control, air quality, fire performance, energy efficiency, and ease of inspection. “Gaps and voids were a big factor before,” he says. “With this SANCTUARY product on the exterior walls, we were able to solve that.”

The SANCTUARY Two-Hour Firewall with Greenfiber FRM also simplifies the inspection process, says Greenfiber Technical Director Aaron Davenport. “From an inspection standpoint you can go into a job that has this product installed, look at it with one eyeball, and say, ‘OK, this product has completely filled the cavity. Check, it works.”

Torres says he’s never failed inspection using Greenfiber insulation in his townhouse projects in Las Vegas. “Our inspectors love it, our builders love it, and our homeowners love it,” he says.

The Evolution of Firewalls

Firewalls slow a fire’s spread from one part of a building to another and are a key requirement in modern building codes. Codes mandate builders use firewalls for dividing walls in multifamily and townhome construction.

The Greenfiber FRM insulation is designed for only the SANCTUARY Two-Hour Firewall, U370 assembly. It must be included in building plans from their inception to guarantee code compliance. This assembly is suited for party walls between units, or any wall where two-hour fire rating is required in townhouses and rowhouses. It’s also recommended for multifamily buildings with three or more stories and mixed-use developments.

In the Las Vegas townhouse development, Battle Born specifies the U370 party wall with SANCTUARY in the exterior walls and spray foam in the room deck. Torres says he chose this hybrid system because “the spray foam hits the most inefficient parts of the home, and the cellulose complements it by giving us Grade 1 every single time on the exterior walls, making it easy for inspection.”

Sharing Walls and Nothing More

When it comes to the options for firewall materials and assemblies, it’s important to consider performance, sound, and air quality, Davenport says. “You don’t want to hear your neighbor, you don’t want to smell your neighbor, and you sure as heck don’t want to be disrupted by a fire from your neighbor,” he says.

Sound and air quality considerations are especially crucial in townhouses where tenants share walls. The SANCTUARY firewall’s ability to seal gaps thoroughly means sounds and odors can’t pass freely between neighboring units, granting homeowners greater control over their indoor air quality.

For today’s architects it’s not enough to address occupant safety—comfort is key. It’s common for landlords of multifamily properties to deal with noise complaints from residents. People who live in townhouses and multifamily homes don’t want to hear music from a party next door or a play-by-play of their neighbors’ TV shows. The SANCTUARY firewall limits sound power by 60%, and Torres says it significantly improved sound abatement in the Las Vegas townhome project. “We not only use the SANCTUARY on exterior walls, but we also use it on interior walls for sound control from room to room,” he says. “The sound control it gives you has been taken very well by our homeowners.”

For acoustic performance, Greenfiber’s SANCTUARY U370 assembly achieves an STC rating of 60—exceeding Gypsum Area Separation Walls with acoustical batts filling all cavities (STC 56–58) and two-hour double wall assemblies with spray foam (STC 57). Since a 3 dB increase is typically considered noticeable, this difference represents a meaningful acoustic improvement, according to Greenfiber.

Keep reading the blog post from GB&D here.