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Looking for help with a factor. I am bidding a staple up radiant loop and the kitchen floor from cellar to kitchen is plywood, Stratamat by Latticrete, mortar (3/8th inch roughly) and tile. Does anyone have experience with this underlayment? resistance to heat transfer? etc... i will be using 1/2" heat pex with aluminum plates. Thanks. Greg


  • kcopp
    kcopp Member Posts: 3,782
    As long as you use the thick extruded plates (not the tinny omega type) you will be fine. May have to add 5* to your output temp but I cant see more than that if your heatloss number came back w/o the need for supplemental heat.
  • hot_rod
    hot_rod Member Posts: 14,865
    Do you have a load calc and design for the room?

    Knowing how many btu/ sq foot you need will help determine what that floor build up can provide.

    Here are some ballpark numbers from that RPA RadPad calculator

    3/4 plywood R- .8
    Stratamat .3
    tile .2

    Call it R 1.5 with some fudge factor

    Room air temperature of 70°, floor surface temperature of 82° = 22- 23 BTU/ sq foot.

    Bare tube staple up by comparison is good for maybe 12- 14 btu/ sq. ft output, so the extruded plates have some real value.

    Be aware with kitchens, only the exposed floor area is considered emitter.

    Deduct any area covered by cabinets and appliances from the rooms floor area.

    How is the rest of the home heated?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream