Am I asking too much from electric radiant floor heating?

jasminetea

We're finishing our basement in a 1920's house.  All the heating on the main levels is old-style radiator heat in a closed system, which I prefer.  Sadly, no vents for AC. 

Because we don't have any vents, I can't figure out how to heat the basement once it becomes living space.  Plus, I don't like blowing heat.  I'd like to go with electric radiant heat (Nuheat to be exact) under ceramic tile but it looks like some folks suggest that it's just for supplemental heat.  The extra electricity load won't be a problem - just had a heavy-up. 

First question, can electric radiant heat be for more than just supplemental heat?  We live in the Washington DC so while the winters can get cold, they don't get too cold for too long. 

For the first time in its life, the basement will be well-insulated so I'm hoping that'll help.

Second question, I'm worried that the radiant heat will costs an arm and a leg for 600 sf basement.  Any other economical options out there?

CMadatMe

Arm and Leg

Willing to bet that electric bill costs you more in the long run...You have a hydronic heat source. Why add more energy when you might have enough already. It all starts with a radiant heat loss, design and quote and work from there. How could you make any decision without having all the necessary information in front of you. Assumptions will send you on the wrong road.

Charlie from wmass

Why not just add radiators of proper size to the basement?

Is it Steam or Hot water heat you have now? Base board heat could also be added. If you do not have insulation under the floor already radiant may not be all the nice no matter the source for the heat.

ScottWarmly

Radiant heat as a Sole Source of heat

Hello Jasminetea,



To answer your question, radiant heat can often be a sole source of heat. To find out, simply visit this link:



http://www.warmlyyours.com/en-US/tools/heatloss-calculator



This tool will help you answer your question. One thing to keep in mind: WarmlyYours' TempZone product offers 15 watts per square foot. Most of the other products in this category use less than that and the calculation will not pertain to their product.



Radiant electric floor heat is perfect for your situation, no blowing air and easy to install. This heat will flow from floor level to ceiling, unlike overhead forced air which only really heats the upper half of the room.



If your basement floor is a concrete slab, I always suggest that an insulator like cork or Cerezorb is placed on top of the slab before putting down the heating wire and tile. This will keep the heat from being pulled down into the slab. A concrete slab acts as a giant "heatsink" and your floor may not heat to expectations. If an insulation layer is used, you will be only heating the tile, not the concrete slab. This will save you money and make the floor warmer faster and it will be hotter than if no insulator is used.



Another way to keep costs down is to use a programmable thermostat. This allows the floor to heat when you are home and reduce the temperature & electricity use when no one is on the floor.



Here is a helpful link for calculating your costs:



http://www.warmlyyours.com/en-US/floor-heating/tempzone/operating-cost



If you decide to go electric, give us a call. We ship same day, give you a free custom installation plan, offer REAL 24/7 technical support and feature the best warranty in the industry. www.warmlyyours.com

tim smith

Re: radiant floor heat for basement

Jasmintea, if this is an old house with basement concreted floor it is unlikely uninsulated under it and around the perimeter. If you do radiant floor on uninsulated slab, you will be heating the worms under your house with minimal benefit and high expense to heat. If you could put insulation on top of the slab or warm board and tubing then you could make sense but you need to give up appx a 1" on height of basement to do so. If you go electric, it will cost a bloody fortune to heat with electric and gas will not be so good either unless insulated. If no room for insulation, go with radiators, maybe Runtal wall panels or the like sized and controlled by a separate thermostat and pump. Good luck, Tim

Gordy

Radiant in basement with no insulation

  Sorry, but I must contradict the statement that radiant will not work with no insulation. 



 Let me be clear.

I think the forum has been weighing heavily on the fact if no insulation is added, or already in place radiant heat will not work. It will, and it has for decades, and I have the situation myself, and it does work.



Caveats apply though. While the best possible scenario is to insulate the slab from underneath, and perimeter to reduce operating costs, decrease reaction time, and lower operating temps thus decreasing operating costs. At the very least if a slab is in place then an insulation breaker between the slab, and the radiant.



  I think it is wrong to imply radiant will not work with no insulation at all. It has in the past.  As specially in a sub teranian basement scenario. Yes operating costs will be higher, yes response time will be longer, and yes operating temps will be higher in a hydronic type setup.



 While the cost of energy, and the supply of it does dictate we need be frugle in our best efforts with its usage, and thus the need to insulate as much as possible in the envelope, and the radiant slab itself. But I still feel the need to be clear that no insulation is not an absolute radiant will not work answer.



Gordy

Jean-David Beyer

Uninsulated radiant heating.

It is pretty certain that my house, built in about 1950, has no insulation under or around the slab it is built on. The slab has 1/2-inch copper tubing in it, and is heated by hot water. Design temperature here is 14F. I heated that hot water with oil from 1976 until 2009. The previous owner did the same from when he bought it new in 1950 until I bought it from him. I did not think the heating bills were too high. I converted to a mod-con gas boiler with outdoor reset in 2009. I now use lower temperature hot water in it and my heating bills are less and the comfort level is higher because the temperature swings are now so small that the thermometer built into the thermostat stays at the set point, so they must be about +|- 1/2F.



Once the slab is at temperature, it does not need to heat the ground underneath any more to change its temperature, only enough to keep the worms warm. There might be some sand underneath the slab; I do not know how effective that might be as insulation. The water table is 6 feet down. I know if it were up near the surface, my heat loss that way could be severe. If the on-going cost of operating your system is a concern, you might want to find out where the water table is in your location. But if it is like mine, you will probably find the fuel bills acceptable and the comfort level high.

Charlie from wmass

Gordy I agree it will work

what I question is the additional fuel cost, uneven temperatures, and the higher water temperatures required for it to function.

Gordy

Charlie

 I do agree with you also.



Gordy

Jean-David Beyer

What do you mean?

"additional fuel cost, uneven temperatures, and the higher water temperatures required"



I am not sure just what you mean. I am not saying you are wrong, but I wonder just how much difference we are really talking about. I have an uninsulated slab to heat my downstairs slab at grade, and a mod-con with outdoor reset.



I cannot tell how much higher my heating cost is compared with what it would be if my slab were insulated, but it seems acceptable to me. I agree that my costs must be higher than if I had insulation, but I do not know if I could ever get payback if I had the house jacked up, insulation installed, and lowered back down. Actually, I assume the whole thing would fall apart.



The temperatures seem quite even if I walk around in my bare feet. My IR thermometer shows some variation, but that may be because I have ceramic tile in my kitchen, carpet with underlay on top of asphalt tile in the living room, marble tiles in the bathroom, and the other two rooms have just asphalt tile on them. And I have turned the valves to each room to even out the temperatures pretty well



As for higher water temperatures, I put 112F water in the slab on design day (14F outside); when it is 52F outside, I need only 75F water into the slab. Maybe they could be less if insulation were there; probably they would be.

Charlie from wmass

a general rule I was taught is

13% of the heat is lost downward unless you have insulation. On the small homes they built after WWII that was not a whole lot of dollars wasted on a heat bill each month. This varies depending on moisture content and soil structure, That is why they would use dry sand with good drainage as the air pockets would slow the heat loss. Heavy clay soils or high ground water levels will drain it even faster. The uneven heat is due to the thermal migration out of the edge of the slab or at any damp spots or odd soil structures under the slab, like shallow ledge. Mileage may vary.

Gordy

JDB

 Charlie is right on JDB. Another thing they did which was done in my basement is stay away from the perimeter 30" with the tubing.  Most of the time furniture goes there anyway.  It all works but the caveat is higher fuel bills as specially in todays market, higher operating temps, and slower response time like Charlie, and I said.



 If your running 112* supply water think what the difference would be with insulation JDB.

Jean-David Beyer

think what the difference would be

" If your running 112* supply water think what the difference would be with insulation JDB."



Exactly! I have been wondering about this ever since I became aware that it is possible to insulate the slab (at least, before it is put in). And that 112F is on design day. When the outdoor temperature is above 52F, the supply water is 75F, and could be even less, but then the boiler short cycles. My thermostats are set to 69F inside.



So it is tough to tell, because when I put in the gas mod-con with outdoor reset, my comfort went up and my heating bills went down even though fuel prices have continually gone up. I suspect the comfort has gone up because of outdoor reset. The bills went down both because of the 60 year newer gas boiler (instead of oil) and the outdoor reset because the slab now runs at a much lower temperature all the time. Probably 30F lower than before. I cannot tell if they stopped the tubing in my slab 30 inches from the edges, nor do I know if they managed to get it near the top of the slab. I do not know how thick the slab is, but it might be quite thick because the top of it is at least 8 inches above the ground, and it probably goes down some. I do know that it melts the snow within 18 inches or so beyond the foundation after a while, so there must be a fair amount of leakage there.



But to figure how much lower the heating bills would be were the slab insulated depends on so many things. Thermal resistance of the soil underneath, distance to the water table, velocity of the water in the water table, temperature differance between the slab and the ultimate heat sink down there, etc. And all I know is that the water table is 6 feet down, which is a lot compared with some places I have seen. I have seen the water there (when they removed my in-ground oil tank).



So all I know is that it now costs about $700/year to heat my house and domestic hot water here in New Jersey, and it cost quite a bit more with oil and an old boiler. So I think about it. If a magician, wizard, etc., were to come by and offer to turn the clock back to 1950, and put the insulation in and then restore the clock to now, how much should I pay him? If I die when I am 100 (27 years from now), do I pay him $210/year? or more? or less? It seems to me that my heating bills are currently acceptable even without insulation. So while I agree that if the O.P. can possibly do it, he should insulate. But if he is as lucky as I am, he might get away without it.

VictoriaEnergy

yes, but.....

Yes, you could apply radiant heat over an uninsulated slab, but you should expect substantially higher heating cost compared to heating it by several other means.   Exactly how much is hard to say.



My first choice in a house with hot water rads would be Runtal or similar style modern rads.  I'd do the heat loss and size the rads for your coldest day demand met with 160 degree water.  All of them would be piped to a separate zone from the rest of the house.  You didn't mention what you have for a boiler, but the near boiler piping arrangement could tie it in with most older equipment.  The system would subsequently run beautifully if upgraded to a mod/con boiler with thermostatic valves to fine tune the distribution plus that li'l Alpha gem you see advertised to the right.



In my view; I believe we will all see much higher energy costs in the future, (esp electricity) and this should be a driving factor in the choices we make today.

Jean-David Beyer

you could apply radiant heat over an uninsulated slab,

At the moment, I am going to do nothing. If the tubing in the slab starts to leak, I expect I will put radiant in the ceiling and cut off the slab. The other option would be to put insulation on top of the slab and the radiant on top of that. But I doubt I would do that because the ceilings are only about 8 feet high, and the thicker I put stuff, the lower the ceilings would be. I have bookcases from floor to ceiling on all the walls where the windows and doors are not, so radiant panel on the walls will not work out.



The copper tubing in the slab has lasted a little over 60 years, so I hope it goes 27 more. I turn off the makeup water when the contractor is not around (he cannot stand having it off) and watch the pressure drop. I have a LWCO, and the controller for my boiler says in some jurisdictions I do not even need a LWCO because the controller notices low water (by timing of temperature differences). But I would not dare to run it with the makeup water off without one. And so far, I can have it off for a month with no pressure loss.