The R4 per inch ComfortBoard IS is the stiff, 4'x8' rigid insulation board for wood frame construction. The 8-lb density board is rated at 743 PSF at 10%) compression resistance to minimize thickness distortion and keep the façade plane straight. It's highly vapor permeable, won't burn, grow mold, and bugs don't like it. It's a great choice for exterior insulation of wood frame projects.


  • The density of Roxul Comfortboard IS mineral wool means that it's no longer air-permeable. It does not have to be in a sealed cavity like low density batts in order to maintain effectiveness.
  • Mineral Wool is hydrophobic. The stone fibers will not take on water and don't have to be protected by an exterior Weather Resistant Membrane (WRB). Place the WRB over the wood sheathing to protect the wood frame in your project. The Mineral wool layer does not need protection when used in a rain screen application.
  • Compression under a batten is an issue to plan for. Even though Comfort Board IS has the highest compression resistance, it will compress easily when a rain screen batten is applied by regular screws. The compression is enough to deform the wall plane and make siding application a problem.  Small Planet Supply stocks various sizes of Heco Topix Therm screws to help minimize this problem. See the video and notes to the right. 

To price a large or small project just give us a call or email: (360) 866-8779 -or-

How To Avoid Compression with the Heco Topix Therm.

Small Planet Supply became the first North Amercian stocking dealer of Heco Topix Therm in 2010. We maintain stock on a range of sizes to apply mineral wool from 1-1/4" to 4" thick. We can special order for applications up to 12" thick. See how the Therm Screw works below.

Heco Topix Therm - How to choose the right size for your application:

  • 120mm for 1/1/4" thick to 2" (3/4" thick batten)
  • 160mm for 2-1/2" thick to 3" (3/4" thick batten)
  • 200mm for 3-1/2" to 4" (3/4" thick batten)
  • Contact us for thicknesses greater that 4". In most cases the batten thickness should increase to increase tear out resistance and shear loads.

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