• <h4 class="dechead">On One Hand: You Can Use Rigid Insulation for Ductwork

    Rigid foam board can be used for ductwork as long as the material has a flame spread index less than 25 and a smoke-developed index less than 450, in most areas of the United States. However, you should check the codes for the whatever authority holds local jurisdiction to make sure your plans meet local requirements. Such codes include the International Building Code, International Mechanical Code, and International Residential Code.

    On the Other: Use of Rigid Insulation on Ductwork Can Be Awkward

    The stiffness of rigid insulation can make insulating a duct difficult, especially on round ducts. Without scoring and bending, rigid foam board cannot adequately insulate ductwork, leaving pockets of air and thermal bridges around ducts. In most cases, it is better to use insulation designed for HVAC applications. Many of these products include a foil layer to reflect heat, sustaining the temperature of the air flowing through the duct.

    Bottom Line

    Though rigid foam board can be used to insulate ductwork, insulation designed for such installations should be used, instead.


    "International Building Code;" International Code Council; 2009

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