I am interested in views from anyone who has installed above-slab, underfloor heating, ie. the style that can be installed under timber/tiles/carpet etc. often referred to as on-demand heating. The economic benefits of the in-slab version are obvious because of the ability to run it from off-peak electricity. The on-demand version however, is designed to give you the luxury of underfloor heating without the required 24-hour heat up time – basically you turn it on and in 30 minutes you have radiant heat. How economical is it, given there is no off-peak concession? Is it economically comparable to other instant heaters eg. wall radiant heaters? Is it an appropriate consideration for an open plan loungeroom/kitchen where you may need constant heating over a 7 hour period. Has anyone used it under timber flooring? Any information would be appreciated, thanks.
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I just built a 2700' ranch & had the plumber install pex radiant tubing under a floor that has 3/4" Avantex subfloor and a Khars engineered wood floor that floats over a sheet of plastic in leiu of 15# felt. The floor is insulated with 6" foil faced (foil up) insulation.
The system uses a Peerless cast iron boiler and a 70 gallon water tank. There are 3 zones upstairs and one baseboard zone in the cellar.
I was originally unsure whether I'd like all wood and slate floors and no wall to wall. Warm wood and tile is as good as any carpet. After a few months we put large area rugs in the dining and living room with no measurable difference in the performance. The house has 9' ceilings and ceiling fans in all but the dining room. I'm very happy with the heat and the A/C (which is a split system).
I'll install a dropped ceiling in the cellar to assure future access to the tubing if needed.
Be sure to get the best tubing that is cross linked to protect it from the effects of the cast iron boiler. Other more efficient european boilers are available but the payback period would be longer than I liked.
Good luck
Was your setup a closed system that recirculated just water, or was it a mixture of water and something else, like antifreeze?
I'm still trying to find out if there is a way to use a tankless approach, and simply heat water being recirculated through the tankless heater. This would make adaption and space savings more amicable to me, but I do not know if it is even possible.
I like the idea of retrofitting this kind of system underneath an existing, finished upper area, but unfortunately here in the South few and little experienced people exist for this kind of methods for heating zones that are per room in nature.
Mine is a closed system that is only water.
There are good radient systems available that will show you all you need to know to start understanding what will work best for you.
My system works best being set at 65 degrees. Thermostat is 4' up the wall and the engineered floor is kept below 85 degrees. It's probably 75 at the floor. I am adding an outdoor temp moniter that will control how hot I should be getting my water. In this area they set the boilers to run at 180 degrees (for a 10 degree day) even when its 30 outside. This linked exterior thermometer will allow the boiler to heat the water only as hot as needed. Before oil reached over 1.50/gallon it was considered too long a payback to bother with. Now its worthwhile.
Go to Google and you'll find a lot of free info. I'm not a plumber but I think that in an aftermarket system one of the most important things is to be sure to buy the right cross-linked tubing and keep the runs from the various manifolds under 250 feet. ( Maybe 300 in your area.)
You could start by checking out some sites like this: http://www.radiant-floor-heating.com/
Good luck
Thanks for the info!
What do you mean to get good tubing that is "cross linked" to protect it from the effects of a cast iron boiler.?
I have a brand new cast iron Crown boiler with 7 overall pump zones in a 3,800 SF house on Lake Michigan. One radiant zone feeds a 8 foot radiant baseboard (piped in 1/2 copper) that I am contemplating converting to in-floor radiant heat, now that I have torn out an old 15 x 20 foot mudset in this master bathroom floor.
My contemplation, do I stay with a copper loop, or go with a pex loop? I will likely add an 1-1/2 inch Gyp-Crete topping, or minimum permissible to bury the copper tubes with the minimum allowable mudset or topping thickness to cover the tubing.
Anyone have a good technical resource for acceptable tubing layout and spacing diagrams?
Waiting to be warm in Milwaukee.