Replies

1. 
   MikeHennessy | Oct 01, 2007 07:00pm | #1

   If you are serious about radiant floor heat, I'd consider hot water in PEX tubing instead of electric. You can embed the tubing in tracks under the finish floor and the heat is the best there is and likely far cheaper than electric to run, depending on your fuel source. PEX is tough and will withstand a lot of abuse. Rolling something around on finish floor is not likely to affect it.

   There are a couple of radiant heat gurus over at Breaktime who will probably respond if you post this Q over there.

   Mike Hennessy
   Pittsburgh, PA

2. 
   frenchy | Oct 02, 2007 07:03am | #2

   Dan

    I'm doing that as we speak.. Your other poster was correct.   Today it's common to use Pex either embedded in concrete or put under the sub floor. the really sweet part is that you can use a hot water heater as your boiler!

     You see boilers operate at over 212 degrees which is too hot for the Pex. they thus condition the water by adding cool water into it..   heating up water and then cooling it down isn't terribly energy efficent in my mind..   however water heaters can operate at 110 to 130 degrees easily which is near perfect temp for in floor radiant 

     By the way in floor radiant heat is far and away the best heat you've ever experianced.. plus it's energy efficent as well.  (has to do with were your heart is compared to your feet.)

1. 
   dan4545 | Oct 02, 2007 12:47pm | #3

   Thanks a lot for the tip.  Pex is definitely the way to go.  Much simpler.  I would think the pump is hooked up to a thermostat?  If so, at what level do you put the thermostat?

1. 
   MikeHennessy | Oct 02, 2007 03:23pm | #4

   The pump is hooked up to the T-stat through a relay or controller, the type depending on your heat source. The T-stat is placed at the normal height - it operates by sensing the ambient temp, not the temp of the floor.

   If you are considering doing this, find yourself a good dealer who can help you properly design the system. Design is everything in a good radiant system.

   Mike HennessyPittsburgh, PA

1. 
   dan4545 | Oct 02, 2007 03:27pm | #5

   Thanks for the tip Mike, I'm searching for a designer as we speak. 

2. 
   saschafer | Oct 02, 2007 03:32pm | #6

   Let me reemphasize Mike's advice to have the system properly designed. There are many, many ways to do it wrong, and only a few ways to do it right. The single biggest error is having runs that are too long.

   -Steve

    

3. 
   rdnzltoo | Oct 02, 2007 10:26pm | #7

   Dan:

   As opposed to another respondent, I would recommend that you key your pump/heat source to the floor temperature, as opposed to a wall mounted thermostat. It is done with a probe that sits on the floor in an unobrusive place (preferably near to the center of the heated area) and is connected to the control via thermostat wire.

   I have done it both ways, and particularly if there is an additional heat source that adds to the ambient air temperature (wood stove, machinery, what have you) you get a much more consistent temperature range in the room when controlling the floor temperature.

   The reason is this: radiant heat (at least in a slab, even a thin one) takes a lot of BTUs to heat the mass, then far fewer to maintain the raised slab temperature. If an ambient source is satisfying a wall thermostat, the mass of the floor is getting cooler and cooler, and it will thus require more BTUs once the heat kicks on again.

   Not only are you wasting BTUs, but the room tends to fluctuate from too warm to too cool. Remember that radiant has a much slower response time than other heat sources.

   Good Luck!

2. 
   tinkerer2 | Oct 03, 2007 04:10am | #8

   There is no heat loss by adding cooled return water to the hot water from the boiler.  Any heat lost from the water is used to heat the room just as it is in a lower temperature water.  With the hotter supply water you also get more energy stored in the water that is available to heating the room - hence less need for pumping the water. 

   Since electric resistance is expensive, you would lose a lot of the advantage of the radiant heat if you had an electric water heater as compared to the other sources of fuel.  One of the advantages of the the radiant heat is that the comfort zone is as much a ten degrees lower as compared to forced hot air.  A rule of thumb is that for every ten degrees in heat rise to heat a room that it will double the heat consumption.  If this is the case, then comparing a given heat loss, one could save up to fifty percent in fuel consumption using the radiant heat.