Radiant Floor Heating

[New Question]

Is it practical to install radiant floor heating in a garage with a concrete floor that already exists? How much do contractors charge for this?

[Edwin Pawlowski]

No How much do contractors charge for this?

Much. Very much.

[Philip Lewis]

Speaking of retrofiting radiant heat flooring... We currently have hydronic (water not steam) heat in the house. I'd like to convert a room or two to radiant flooring. (I'd also like to zone the house a bit while i'm at it)

I have two questions:

1: Is it reasonable to install a manifold system with the flexible tubing i've seen put in for RHF that will interface with the current iron pipes? I envision the following: Boiler (large iron pipe) -> Interface (Iron pipe -> small flex pipe) ->

Split into several flex pipes with solenoids (inc 1 bypass zone) ->

Interface to Iron fittings for each radiator ->

Returns (could leave returns joined to boiler.)

I think that the problem would be that the return water would mix and cool unless i disconnected asap after the radiator and remerged back near boiler.

2: The rooms most likely to retrofit are on the first floor. I have access to the floor joists and think i could use the "plate" type radiators. Do i understand correctly that the RFH temp is likely much less than the current boiler temp (??? cool enough to sit upon). Could i just get by with less tubing in the circuit, should i put insulation between the tubing and the floor to prevent "too hot to walk" spots, or should i have a resevoir that mixes the return water with the hot water and only cycles the boiler when *that* temp is too low?

The flooring is mostly hardwood and their appears to be another plank wood (not plywood) subflooring between the visible hardwood and the basement.

I'm also considering replacing the main boiler at some point with a more efficient model... perhaps with a cogen unit if i can find one for sale in the US. The idea of putting in a manafold and zoning now is basically in in preparation for that time. (essentially i want a self contained heating system that would cycle the "external heat source" as needed (boiler in this case, but possibly solar in the future)) I imagine i could install the RFH in parallel with the radiators and I could use a heat exchanger to source the radiant floor loops... that might reduce the number of iron/flextube interfaces.

Thoughts?

Any brand recomendations for the "plate" emmiters?

Other technologies?

Am I crazy? (Please limit your evaulation to ideas presented in this post. :)

[m Ransley]

Anything is practical if you have the $. But you will raise the floor and need thick enough concrete to not crack with the hose reducing its thickness and strength. A wall heater would be more practical and cheaper.

[m Ransley]

Boilers run from 120 - 195 to output usable heat, I believe tubing for floors can take only 110 or so. Your boiler now probably gets to

170-180 when real cold out, you need some way of controling the max temp of the radiant system and leave the boiler at its higher temp, some type of thermostat pass through. Radiators could not be on the same piping I believe, or they wont get hot enough.

[Ed Clarke]

Yes it's reasonable and no the way you're trying to do it won't work. You don't want more than 80 degrees on the floor. Start here:

and think things out carefully. I'm about to do this myself.

[HeatMan]

Is it practical? Only your wallet knows...

How much? See above answer.

[HeatMan]

Your kinda on the right track. You would need a mixing valve installed. I'm bidding on one quite similar to the one you're talking about now.

Actually, it's a piece of cake.

Are you talking about the extruded plates of the flashing type plates? Big difference...

Your water temp with radiant will probably be less than 105°

See the second answer I gave...

Still easy.

Cogen isn't that affordable here yet. Too long of an ROI, in my opinion.

You won't need a HX if you already have a boiler.

You see them above.

Joist Track from Wirsbo are the ones I use.

If you get a new boiler, get one that has outdoor reset. Heat Transfer Products makes an excellant high efficiency boiler.

Except for the cogen thoughts, I don't think so.

[HeatMan]

I'd be real careful about these guys......

[Philip Lewis]

Hmm... nice site, thanks.

From what i read there, i believe i wasn't far off and it is possible. Easiest way seems to be to use a heat exchang>Boilers run from 120 - 195 to output usable heat, I believe tubing for

to indicate 120-145 degF. Same page seems to indicate that if installed in a hanging enviroment, it can take boiler temp water of

180. They say that this (hanging with airspace) is not a radiant panel association approved method of install although to indicate that it is.

I looked at my boiler, and it has a temperature setting that allows variation from 75 degF to 225 degF. It is currently set at around 180.

Some specs on the current boiler: Naional US Radiator corperation (last in bus under that name in 1955) BTU/hr Water = 130,000 (old uninsulated victorian... need to fix that) AGA rating input (BTU?)=218,000 output = 172,800 (does that mean efficiency is 172800/ 218000 = 79% or 130000/218000 = 59%??? for as old as the boiler is, i'm guessing 59%... Either way i'm guessing that a new boiler would help our heating bills. ;)

It says the gas is equiped for gas@1100 BTU/hr... How does 1100 BTU of nat gas produce 130000 BTU of heat? I believe I'm missing something. (perhaps I misremembered and it said 1100 cubic feet/hr?)

Any opinions on the monitor mz boilers? (from the houseneeds site) preheating the domestic hot water might be nice. (the indirect storage tanks seem awful pricey)

Any recommendations of other brands that have a good value/price ratio? I'm reading up on some at

but i live in Pittsburgh PA, USA... so not all models may be available.

It's a shame about cogen being scarce/pricey. Seems like a natural for winter use in a hydronically heated house.

[m Ransley]

Overheat the tube and it weakens leading to failure-leaks. That is why you have a max safe temp for tube. Run your boiler at 110 you wont heat your house . A separate thermostat valve would do.

[Philip Lewis]

So... I didn't get a response in the radiant heat thread, so I'll ask in a new thread. I have the following boiler:

**************** National US Radiator corperation Lists the output at 130,000 BTU/hr (Water) but then lists a "AGA ratings" for input =218,000 and output = 172,800 ****************

Does that mean efficiency is: 172800 / 218000 = 79% or 130000/218000 = 59% or are the figures I've quoted nonsensical??? (I'm fairly sure the AGA ratings were BTUs)

For as old as the boiler is (last in business under that name in 1955), i'm guessing 59%... Either way i'm guessing that a new boiler would bring a ROI fairly quickly.

It also says the unit is equiped for gas@1100 BTU/hr... How does 1100 BTU of nat gas produce 130000 BTU of heat? I believe I'm missing something. (perhaps I misremembered and it said 1100 cubic feet/hr?)