Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Underfloor Radiant Heating vs Sandwich/Warmboard/above floor

sniz Member Posts: 5
Is there a big difference between the beneath floor heating and the sandwich style in floor heating methods? I'm looking for efficiency/complication differences.


  • hot_rod
    hot_rod Member Posts: 19,935
    It comes down to how much wood thickness you need to drive the energy through. The closer to the finished floor the lower the supply temperature and the faster it will respond to a heat call, or when it satisfied. The low mass tend to be more control-able, better suited for areas with big or frequent load changes, less over-shoot. So technically lower SWT could equate to lower operating costs if a mod con is the heat source. The dry/low mass seem to be a better option in moderate climates.

    The cons, no thermal mass, possible more on off cycling compared to medium or high mass slabs.

    Also the work involved in installing the various systems. Working over-head or on hands and knees? Obstacles to work around below the floor, pipes, wires, duct work, drilling of joists, insulation detail, etc.

    The "dry" over the top systems tend to be easiest to install, and plenty of options. I like the Roth Panel system for on top. All aluminum cover, thin product, easy to cut and glue down. The foam panel gives the floor a nice feel for walking over. ThermoFin are great if you want to customize as system, under or above the floor.

    With any on top system you may need to deal with stairs, baseboard trim, door openings, you lose some kick space under cabinets. Possibly lock in your dishwasher from easy removal :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • TAG
    TAG Member Posts: 751
    Hot Rod knows all the numbers and has endless resources and often will post pictures of different systems running.

    For me it's always come down to what is possible. I'm an old house nut so doing the under floor retrofit plates has been the norm as all the trim and stair heights are too much of a problem. I have used a few different types of plates over the years .... Thermofins that Hot Rod referenced early on became my go to plate.

    You have to look at a room by room load -- as long as you can get the BTU's per foot out of the system for your needs -- anything will work.

    On new work I have used Warmboard -- the subfloor product. I have used this over a new slab on a single floor addition as well as all new construction and in places where floors needed to be replaced in a old house. It's a great product .. also typically the most cost. I did do one Warmboard R in a basement area over insulation.

    One of my last projects using mostly Warmboard -- I used the heavy plates just because with those I was able to keep the temp of the water close to that of the Warmboard and this allowed me to use only one temp water for the whole house.

    I have also had situations where the plates were not going to give me enough BTU's -- this was an 1810 federal in Philadelphia that I did years ago. Not a lot of insulation in those old walls .... I had to have supplemental heat -- ended up using some panel radiators.