Adding radiant floor heat to addition

try1355

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 

hot_rod

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 

GroundUp

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.

Big Ed_4

Like HR said , it's good for a few parts .

eauciel

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. 

mvickers

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

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.

hot_rod

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.

Mad Dog_2

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 🐕 

SummitMechanic

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.