Tough Fire Code Demands Insulation Innovation

Stone wool insulation handily meets new code for fire-resistant I-joist assembly.

As of May 2016, every state except Wisconsin has adopted more stringent fire protection of I-Joist code based on 2012 IRC section R 501.3, which is great news for occupant safety, but has many builders worried about added costs.

“The fire code is difficult; it’s a big deal,” says Matt Risinger of Austin-based Matt Risinger Homes. “Previously we didn’t need to do anything for locations such as unfinished basements, so this has gone from zero to having to spend some money. Builders want to know how they can meet code without pain or cost.”

According to Risinger, there may be a silver lining to the situation. The new code actually offers the opportunity for builders to provide safety and peace of mind for home buyers while also offering a host of other benefits if they spec Roxul Safe’n’Sound stone wool insulation. The product meets code for fire protection of I joist assemblies.

As detailed in the video at the bottom of this post, Risinger shows how easy it is to meet the new code in unfinished basements by installing Roxul mineral wool insulation and foregoing a more expensive and limiting gypsum solution. “The thing I like about using Roxul to meet the fire code is that it is not irreversible. If you use gypsum then down the road you won’t be able to access pipes for repair or upgrade without cutting out drywall. If you use mineral wool batts, like Roxul, you can pull the batt down and do the work and have it back up in five minutes.

If you are wondering how an insulation product can be as fire resistant as gypsum, recall what mineral wool is made of: spun rock, and like rock, it is an excellent fire suppresser. It does not develop smoke or promote flame spread, even when directly exposed to fire up to 2150°F.

Related story: Fire Resistance Big Asset in Insulation.

As an added benefit, Roxul’s high-density batts provide better sound absorption at low and medium range frequencies an added bonus that homeowners will enjoy.

“As builders we are constrained with cost and limited profit margins,” says Risinger. “There are limits to what people will pay for. This is a solution that meets regulations and offers clear benefits to the homeowner.”

Easy Steps for Code Compliance

codewatcher-roxul-basement_i-beamThe diagram at right shows how mineral wool can be used in place of a gypsum solution to meet codes. The following assembly was tested and approved to provide alternate fire resistance per the 2012 IRC, section R 501.3, exception 4. The system was tested per ICC Acceptance Criteria AC-14 section 4.4, following ASTM E119.

Installation Instructions:

  1. Follow Roxul instructions on personal protection equipment.
  2. Install batts between joist webs, on top of the bottom flanges. Use batt widths that correspond to joist spacing. Use minimum 15.25”, 18.5” and 23” widths, when I-Joist 3. spacing is 16”, 19.2” and 24” on center, respectively.
  3. Install batts snug around any pipes located in the cavity.
  4. Use rigid stay wires between bottom flanges, 24” on center and no more than 4” from ends of batts.

For more information, you can download Roxul’s compliance guide here, or contact your Roxul sales representative today at 1-800-265-6878 for more details.

Benefits of  Safe’n’Sound:


  • Non-combustible stone wool insulation with melting point of approx. 2150 °F (1177 °C)
  • Cuts easily
  • Excellent sound absorbency
  • High density batts provide for better sound absorption at low frequencies
  • Fire-resistant due to its high melting temperature
  • Chemically inert
  • Water and moisture resistant; does not absorb moisture to maintain insulating value
  • Does not rot, promote mildew, fungi, or bacterial growth
  • CFC- and HCFC-free product and process
  • Made from natural and recycled materials