Insul-Cube Testing Proves Air Blocking Ability in Third-Party Testing

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National Fiber’s NEW Insul-Cube Rim Joist Insulation System is third-party tested for air blockage. Passes with amazing results.

“I have used the Insul-Cube since it came out knowing it was doing a great job insulating. These test results only prove it!” -Littleton, MA Weatherization Contractor

National Fiber’s patent-pending Insul-Cube™ was recently tested by The Green Jobs Training Center in Howard Beach, NY. In a testing apparatus developed by Mike Dunseith at the center, the Insul-Cube was put under direct air pressures of 50 pascals.

When directly installed to the simulated rim joist, and filled with cellulose, the Insul-Cube completely blocked the air flow at 50 pascals. When the Insul-Cube was filled outside of the rim joist and then pushed into place, after caulking the connections in the rim joist, again there was no air penetration at 50 pascals.

This breakthrough testing proves why the Insul-Cube is fast becoming the product of choice for rim joists and other areas where superior thermal performance is needed. The Insul-Cube is a cube shaped product that is filled on-site with cellulose, and installed in the rim joist. The material is a class A/1 fire rated product that can be left exposed. The Insul-Cube makes insulating the rim joist quick and easy reducing labor and clean up.

During the testing, the Insul-Cubes were very quick to fill and install. The Insul-Cubes fill and installs in approximately 10 seconds. The thermal superiority of the Insul-Cube is what really makes the difference. Fully filled, the Insul-Cube is an R-49.

Insul-Cubes are now available for purchase online! Visit for all Technical and MSDS information. Insul-Cubes are available in boxes of 200 each. A box of Insul-Cubes will typically do 1 large house or 2 smaller houses. One contractor stated, “I was weary of trying such a simple product, but when I did, the Insul-Cubes are a huge time saver that it saved me not only time on the job but money as well. If you have not tried them yet, do yourself a favor and try them out. Your wallet will be glad you did.” For more info about the performance tests and data sheets, visit

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Christopher White
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