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.

Adding radiant floor heat to addition

Options
try1355
try1355 Member Posts: 1
edited August 2023 in Radiant Heating
Currently having a 20x26 addition put on our home. The bottom portion (rec room) will be concrete floors with creatherm insulation. Contractor got me a used manifold that I will be installing for rec room heat. My question is would I be able to modify this current setup to also run pex in between the floor joists so that I can also heat two 12x12 rooms that will be above the rec room? Using an outdoor wood boiler that runs from my furnace to my hot water tank (heat plate exchanger), then to this and back to the boiler. Any help would be appreciated..Thanks 

Comments

  • hot_rod
    hot_rod Member Posts: 22,394
    Options
    The first step is to get a heat load number for all the rooms  you want to heat

    Next is the design step, this tells you what temperature you need to send to the various rooms, tube spacing, flow rate, etc 

    It probably will require two temperatures so that panel would need some mods. Certainly some useable parts there 
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    try1355Mad Dog_2
  • GroundUp
    GroundUp Member Posts: 1,941
    Options
    You're going to have neverending airlock problems with the upper loop(s) if you attempt to use this setup without an additional plate exchanger for the radiant. As hot rod said, the upper level would also likely require a higher water temp than the slab so aside from the circulator, you'd probably be time and money ahead starting over new if you want to do it properly. If you don't care about temp fluctuation, it's possible to reuse exactly what you have and simply run the same temp fluid through both levels as one zone. You'll still want a heat exchanger either way though, or you'll be chasing airlocks forever.
    try1355Mad Dog_2
  • Big Ed_4
    Big Ed_4 Member Posts: 2,819
    Options
    Like HR said , it's good for a few parts .

    There was an error rendering this rich post.

    Mad Dog_2
  • eauciel
    eauciel Member Posts: 5
    Options
    If the heat load varies between two different spaces, consider adding more pipe per square foot as required to compensate. 
    May require an extra zone. 
    Mad Dog_2try1355
  • mvickers
    mvickers Member Posts: 30
    Options
    Reflecting on radiators bec I wasn't really satisfied with doing staple up radiant in my previous house.
    And now that I'm in my, way down-sized, hopefully last house, 1K+ sqft, single story, 16" thick boulder stone walls on slab.  I'm storing radiators for installation, hopefully in the near future, and flipping a coin as to how to run the series-parallel piping, but staying out of the attic space.  Cutting channels in the concrete doesn't sound like much fun, esp with possible future problems, and exposed down pipes from the attic leaves me with old time, tenement apartment pipes, ala The Honeymooners, or some sort of decorative covers.  One way or another, the currently tiled floors will be redone in prefinished, 9mm, floating t&g.  I've also considered 1" sleepers to run radiant.

    Any & all suggestions welcome

  • KenMez_2
    KenMez_2 Member Posts: 8
    Options
    When I added radiant heat in my kitchen via slab I did not realize that my boiler was undersized to accommodate the addition. I now live with condensate dripping down my wall during the heating season.
    Mad Dog_2
  • hot_rod
    hot_rod Member Posts: 22,394
    Options
    mvickers said:

    Reflecting on radiators bec I wasn't really satisfied with doing staple up radiant in my previous house.
    And now that I'm in my, way down-sized, hopefully last house, 1K+ sqft, single story, 16" thick boulder stone walls on slab.  I'm storing radiators for installation, hopefully in the near future, and flipping a coin as to how to run the series-parallel piping, but staying out of the attic space.  Cutting channels in the concrete doesn't sound like much fun, esp with possible future problems, and exposed down pipes from the attic leaves me with old time, tenement apartment pipes, ala The Honeymooners, or some sort of decorative covers.  One way or another, the currently tiled floors will be redone in prefinished, 9mm, floating t&g.  I've also considered 1" sleepers to run radiant.


    Any & all suggestions welcome

    The challenge with retrofitting floor radiant over an old slab is the insulation detail.
    Ideally you want 2" below a new slab or any system really.

    There are foam panels like the Roth system that work well, you need to accommodate the 1/2" plus the final flooring height. But even with a 3/4" floor build up, that can interfere with doors, base trim, exterior entries, and stairs, etc. And not much R value from the current slab either.

    Radiant ceilings are another nice option, the same radiant "feel" just from above.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Mad Dog_2
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,208
    Options
    You're on the right track. Radiant can't be matched!  When you try to build anything around a used part you're DETERMINED to USE!!!, you often start to do strange things to accommodate this one USED item that costs a few hundred dollars.  

    Listen to the boys...do your load calls and follow from there.  Don't base the whole job on trying to use that manifold.  Ask me how I know.  Mad Dog 🐕 
    try1355
  • SummitMechanic
    SummitMechanic Member Posts: 25
    Options
    You can modify anything,but that setup is build where it is actually easily modified for your purposes. I would suggest adding a drain to both the supply and return manifolds when you do modify them to ensure easy purging and draining in the future.
    Experienced Boiler Mechanic In Summit County, Colorado.
    try1355