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Insulation for Ultrafin

COresidentheathelp
COresidentheathelp Member Posts: 1
in Radiant Heating

Does anyone have any recommendations for specific insulation product for Ultrafin radiant heat? We have an 11 inch joist bay, our HVAC contractor wants something that is no thicker than 4 inches to create an adequate cavity to allow appropriate convection in the hoist. The insulator sent a quote for R11 unfaced 4 inch - would this work? Does this need to be faced or foil faced? Or if anyone knows of something better for ultrafin insulation, I would appreciate your advice. Thanks!

Comments

  • hot_rod
    hot_rod Member Posts: 23,270

    Why not a 6” or 8” batt? The more r value you have, the less heat will travel downward

    Unfaced batts are fine, no need for foil faced either

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Alan (California Radiant) ForbesRich_49
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,212

    We always recommend Rocksul (aka Rockwool) for Ultra-Fin. A step up from fiberglass.

    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    Rich_49

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