After several large-scale hotel and nightclub fires in the mid-20th century that resulted in the tragic loss of life, fire safety and building design professional organizations created testing methods to rate materials based on how quickly they burn and develop smoke. Today, model codes developed by the International Code Council (IBC) and the National Fire Protection Association (NFPA) reference NFPA 285 as the test standard for exterior wall assemblies.

Development of NFPA 285 started in the 1970s in response to the increasing use of foam plastic exterior insulation in exterior wall assemblies to achieve compliance with increasingly strict energy codes. The test method evaluates how flames propagate on an exterior wall assembly subjected to a standardized fire exposure. It simulates a two-story wall assembly with an opening to simulate a window on the first-story wall, and the floors are separated by a floor assembly. NFPA 285 assesses flame propagation: 

  • Over the exterior wall surface
  • Within the combustible core or components
  • Over the interior surface from one floor to the next
  • Laterally to adjacent compartments

A growing emphasis on energy conservation has led to increased use of combustible, synthetic materials such as foam plastic insulation and water-resistive barriers to boost the energy efficiency of buildings. Additionally, aesthetic preferences for a sleek, modern appearance have resulted in combustible veneers being used on high-rise buildings. Combustible materials including foam plastic pose challenges to meeting the NFPA 285 standard.

Stone wool continuous exterior insulation provides a solution for meeting NFPA 285, energy codes and sustainability goals.  

  • Fire resistance – Naturally fire-resistant, stone wool can withstand temperatures above 1,800°F to contain fire and prevent its spread.
  • Thermal properties – Stone wool maintains consistent and long-term thermal performance over the life of the building.
  • Sustainability – Stone wool can be indefinitely recycled and does not include fire-retardant chemical treatments.

ROCKWOOL stone wool insulation provides a high degree of design freedom to build energy-efficient, fire-safe and aesthetically pleasing buildings that provide healthy places for living and working. Read our technical bulletin to understand how to use our products to meet NFPA 285.

NFPA 285 testing is time-consuming and expensive, so ROCKWOOL offers a wide range of wall assembly options. ROCKWOOL Comfortboard 80, Comfortboard 110 and Cavityrock assemblies meet the requirements of the NFPA 285 fire test method. Additionally, these assemblies  provide architects the option to choose from a greater range of cladding and weather-resistant barrier options because stone wool protects vulnerable components behind it.  


ROCKWOOL Comfortboard

Comfortboard 80 and 110 assemblies meet the requirements of the NFPA 285 fire test method. 

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ROCKWOOL Cavityrock

Cavityrock assemblies meet the requirements of the NFPA 285 fire test method. 

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California building code, Title 24

California building code, Title 24, sets strict requirements for energy efficiency and fire safety. See how ROCKWOOL stone wool insulation offers solutions for architects navigating these demands, especially as they pertain to wildland-urban interface (WUI) areas.

California state map