Firewalls & Fire Resistance

Class A Fire Rated Insulation

Nu-Wool Premium Cellulose Insulation is one of the few construction materials used in houses that is treated for fire resistance. Because it is a fire resistant insulation, Nu-Wool Premium Cellulose Insulation stops or slows the spread of fire in attics and wall cavities. Plus, the fire retardants used in Nu-Wool insulation products last the life of the structure.

Fire Retardant Permanency

Fire retardants used in Nu-Wool Premium Cellulose Insulation do not lose their effectiveness over time. Tests by scientists and technicians at Oak Ridge National Laboratory, Tennessee Technological University, Allied Signal corp., US Borax Corp., Underwriters Laboratories, and United States Testing Company, found no sign of “disappearing fire retardants.”

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    Helpful Information


    2.5 or 3 Hours of Full Load Bearing Fire Protection

    Our UL-classified U382 Firewall is a proprietary design of Nu-Wool Co., Inc. that is fully load bearing and offers two and a half or three hours of protection that costs less, and saves more than other solutions on the market.

    The U382 meets all the requirements of ASTM-E-119 and ANSI/UL 263. The U382 meets the requirements of firewall assemblies, and the independently loaded double wall assembly maintains its integrity beyond the nominal one-hour per side, giving the U382 a two-hour and thirty minute rating with only one layer of 5/8 inch type C gypsum board on each side. A 3-hour rating is achieved by using 2 layers of gypsum board on each side.

    Nu-Wool Co., Inc. developed WALLSEAL Fire and Sound Insulation specifically for use in the U382 firewall assembly. Light green in color, WALLSEAL Fire and Sound Insulation has the same superior thermal and sound control properties of Nu-Wool Premium Cellulose Insulation.

    STC tests were also done on three configurations of the U382 assembly: One using one layer of gypsum board per side achieving an STC of 53. The second test added one layer of gypsum board to one side and this wall assembly achieved an STC of 58. The third test for STC used two layers of gypsum board per side and achieved an STC of 63.

    U382 Firewall Nu Wool
    Firewalls U382 Rendering

    Industry Leading 2.5- or 3-Hour Firewall

    Design No. U382
    Using 2 or 4 layers 5/8in. Type C Gypsum Wallboard
    Underwriters Laboratories Bearing Wall Rating: 2-1/2 or 3 Hr.
    Riverbank Acoustical Laboratories STC Rating: 53, 58, 63

    Download the Firewall Tech Sheet

    Wall assemblies insulated with Nu-Wool Premium Cellulose Insulation was tested at Riverbank Acoustical Laboratories for Sound Transmission Classifications (STC).
    Download the Full Report»

    Other Cost Saving Firewalls

    In addition to UL Design U382 described above, Nu-Wool Co., Inc. has engineered two other proprietary UL-approved, cost-saving firewall designs. UL Design U360 is a 2-hour, load-bearing firewall tested by UL that needs only three layers of 5/8″ type X gypsum board resulting in savings of 25% on drywall labor and materials. Sound-absorbing UL design U369 has a high STC rating of 58 making it the design choice for sound control. All three of these innovative fire walls with limited layers of gypsum board successfully pass the stringent requirements of ANSI/UL 263 and ASTM E-119 because of the high density of Nu-Wool Premium Cellulose Insulation installed using the Nu-Wool WALLSEAL System, which slows the spread of fire by restricting the availability of oxygen. Nu-Wool Premium Cellulose Insulation has also been approved for use in over 50 additional UL listed firewall designs.

    Firewalls U360 Rendering

    Cost Saving Two-​Hour Firewall

    Design No. U360
    Using Only 3 layers 5/8 in. Type X Gypsum Wallboard
    Underwriters Laboratories Bearing Wall Rating: Rating 2 Hr.
    Riverbank Acoustical Laboratories STC Rating: 51

    Firewalls U369 Rendering

    Sound Absorbing Two-Hour Firewall

    Design No. U369
    Using 4 layers 5/8 in. Type X Gypsum Wallboard
    Underwriters Laboratories Bearing Wall Rating: 2 Hr.
    Riverbank Acoustical Laboratories STC Rating: 58

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    Nu-Wool is not only the GREEN choice but the superior choice for insulation in your home. Our insulation (3.8 R-Value per inch) is installed in walls, attics and floors of new & existing houses.

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    Energy Savings Calculator


    The use of this calculator is limited to comparisons between energy costs of example homes only. The numbers shown do not represent actual dollar amounts or dollar savings from Nu-Wool Co., Inc. Your savings may vary. The calculations are based on typical new home construction, state average utility costs, new high efficiency HVAC systems, and typical weather for the state selected. These numbers do not include base utility costs such as water heating, lights, and appliances. If you have questions, please contact the Nu-Wool technical department at (616) 669-0100.