Radiant Heat in Cement Floor

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  #1  
Old 01-26-05, 10:27 AM
howz
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Radiant Heat in Cement Floor

If I have radiant heat in my basement floor, can I put ceramick tile, hardwood, or laminate directly over the cement floor or should I be putting some kind of sub floor down?
 
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Old 01-27-05, 10:09 AM
123456
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I don't know the answer to this, but I am also in your situation. I would assume that any subflooring you put down will reduce the amount of heat that gets to the living space. When we do our basement, we are not planning to put down subfloor. I assume that you are planning to use the lock together or glue down flooring?

More ?s on the same issue......
If you put down carpet, will you still get sufficient heat?
Can you glue down carpet tack strips?(with heating tubes, I can't nail into the concrete)
 
  #3  
Old 01-27-05, 10:54 AM
howz
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Yeah, probably the fake hardwood. We have a ton of hardwood upstairs and plan to go cheaper down stairs. I think it's ok to put finish floor directly on the cement but I just wanted to make sure.

Carpet is fine, it's not as good as tile or hardwood but it's fine. I have radiant heat on my main level too and two bedrooms carpeted. Just don't go too thick with the underlay (even then it's not that big a deal).

I would suggest calling a carpet retailer or flooring place to ask about gluing the tack strips.
 
  #4  
Old 01-27-05, 11:33 AM
123456
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You have me curious about your upstairs radiant heating. Is it electric or water tubes?
If water, is in a concrete substrait or just stapled up to the bottom of the wood subfloor?
I ask because we have hot water baseboard heat upstairs and have looked into running water tubes under the floor.
Again, just curious.
 
  #5  
Old 01-27-05, 12:17 PM
howz
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It's the hot water tubing. Not sure if you are building or renovating, but the best and most efficient is cement on the main level. I went cheaper and ran the tubing in the joists. I wouldn't attach it directly to the plywood if you plan to lay any hardwood. I ran the tubing down each side of the joists and attached the tubing about 3" from the plywood. We have two bedrooms carpeted, bathrooms and entry way ceramic tile and the rest hardwood. Real nice on the bare feet, especially on those cold winter mornings. Our 11 month old takes some nasty headers on the tile and hardwood though. You do a lot of chancing

Don't know much about the electric, I'm guessing it costs more to run ...
 
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Old 01-27-05, 01:08 PM
123456
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That is how I was looking at doing a retrofit to our existing home, to put it under the flooring.
Do you run it off of a boiler? It was recommended to me to run it at a lower temp (~120) than the typical 180 degree boiler water.
Is that your only source of heat for the main level?
Is it proving to be a cost effective way to heat?
We do have a lot of carpet in our house, so maybe that is an issue.
AT 11 months, they take headers off of everything, don't they!
 
  #7  
Old 01-27-05, 01:27 PM
J
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Don't use Carpet

Radiant Floor heating systems rely on direct exposure of "Non-Insulating" material to transmit the heat. Essentially, this type of heating does not directly heat the air but heats the floor itself. The floor then radiates this warmth to people who are near it. Carpet is an insulating material and fails miserably in this regard.

In fact, the typical laminate flooring installed over a foam membrane is also a poor choice for the same reason. The best choice is Stone or Tile because these materials will actually get warm - like a sidewalk in the summer. Hardwood glued to the concrete is the second choice - direct contact to the warm slab will allow the wood to transmit the heat thru it - but it might result in differential expansion and swelling. Wood on sleepers is better than carpet or the laminate flooring over foam, but not much.

Remember, the radiant floor heating is really intended to be used only when people are or will shortly be present. The idea is to warm the floor and allow this warmth to be radiated to the occupants. If the floor is cold it will be like sitting directly next to a cold window. If it's warm it will be like sitting next to a radiator. This will be the effect regardless of the temperature of the air in the room. If you place a sheet of insulation between you and the warm surface you will get no feeling of warmth - don't use carpet.
 
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Old 01-27-05, 01:40 PM
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Wink

Just dumb info : Did a home with hot water heat in the cemecnt floor. Worked real good but for a bed room. the lady call up come fix it. She had put a rug with a pad down on the floor. If you felt under the rug it was hot but no heat in the room. She had to have the rug down so we had to add in some more baseboard in the room to keep it warm for her . Such is life

ED
 
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Old 01-27-05, 01:52 PM
123456
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I just read that Armstrong laminate flooring recommends no more than 80 degree surface when installing over in floor heat. I don't know how warm our basement floors are when the heat is on, but it is worth checking.
 
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Old 01-28-05, 05:19 AM
howz
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123456, I have mine run off an oil fired boiler. There are separate supply and return manifolds for the upstairs and basement. I have 5 zones. (1 Garage, 2 Basement, 2 Main Level) Yes, it is my only source of heat for each level. Like I said, I have carpet in two bedrooms. Ed and Joe are saying no carpet. Out of 1800 square feet, the two bedrooms only account for 400, so maybe that's why the carpet has little effect. Eventually, when my children grow up, I will get rid of the carpet. But for now, my heat is still working great. I was told I needed engineered hardwood floor. I put down regular hardwood. It's fine. In the winter the joints between the pieces opens up more but no biggy.

Yes, my boiler is set at 120 ...
 
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Old 01-28-05, 08:44 AM
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The joints in your hardwood floors are most likely "opening up" in the winter due to low humidity more than the heat - although they are related.

Most radiant systems are designed with most of the heat at the perimeter of the room - but preferably not under furniture. If a rug is placed in the center and doesn't cover the heated surfaces it would be fine. Wall to wall carpet - particularly thick carpets and pads - is just too good an insulation.

It's interesting to note that radiant floor heat has been around for a long time but during the 1950's when carpet became so popular this type of heat lost favor and most homes were built using FAU's. Now we find that Carpet and FAU's causes a lot of airborn dust and other alergy problems so hard surface floors and radiant heat is coming back in favor.

Properly installed and used, radiant floor heat is extremely efficient. The energy savings will definitely pay for the installation costs over a period of 5-10 years.
 
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Old 01-28-05, 09:11 AM
howz
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Joe,

You know your stuff about radiant heat. I would like your opinion on something. As mentioned earlier, I have the tubbing in the floor joists under the main level. How would you insulate the tubbing in the floor joists. Would you stuff reflective in the joist and then 6" bats of fiberglass? Would you only use reflective (although little r-value)? Or would you use only fiberglass?
 
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Old 01-28-05, 09:32 AM
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I assume you mean the tubing is between the joists directly below the sub-floor.
Placing a reflective membrane below the tubing is appropriate. If this is an unheated basement or crawl space then it also needs insulation uder the reflective membrane.

Personally I don't like fibreglass batts in any location where mice might be able to get into it. One option would be to get foil-faced rigid insulation and cut it to fit snuggly between the joists. Since it comes in 1" to 3" thickness, you should probably also use additional thicknesses of insulation to get the required R value.

At the same time, with radiant heat you don't need to worry nearly as much about heat loss as you would with a Forced Air system. IOW, Insulation is not nearly as critical.
 
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Old 01-28-05, 10:13 AM
howz
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My basement is not heated, but it is quite warm ... only little bit cooler than up stairs. If I understand you correctly, the reflective is all I need if the basement is heated? Should I turn the heat on in my basement. I thought I would be wasting money since it's unfinished.

PS: What do mice do in the fiberglass? Make nests?
 
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Old 01-28-05, 10:40 AM
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What I mean by unheated is:

Open Ventilation to the exterior, uninsulated walls, etc. If your basement is equiped with heating capability then it would not qualify as an unheated space.

Yes, mice make nests in the fibreglass batts and basically destroy it. They love the stuff.
 
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