Is there a Disadvantage to Underfloor Heating?

Discussion in 'Remodel Forum & Blog' started by herbolaryo, May 31, 2007.

  1. herbolaryo

    herbolaryo New Member

    Messages:
    31
    Location:
    San Francisco
    I have seen underfloor heating ---electric and those with water pipes...

    1. Is there a disadvantage to underfloor heating?:confused:
    2. Since it will be placed underneath ceramic tiles or hardwood which is permanent, will future repair be a problem?:confused:
    3. Since there is heat, will growth of bacteria of molds be faster?:confused:
    4. What is the brand/model is the best underfloor heating?:confused:
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,059
    Location:
    New England
    It is probably the most comfortable method of heating. You don't have restrictions on where you can put the furniture. It costs more to install, but usually less for energy. If you want a/c, you can't share the cost with the air ducts already there for heating. If the pipes don't leak (and they shouldn't), they are a closed system that gets heated fairly hot so you shouldn't have anything growing in the water. Shouldn't be a problem. Same idea as radiators...you don't really care.

    Electrical heating mats also should last. While you can use them as primary heat, that may only apply in mild areas. They are usually restricted to a maximum of 12W/sq foot - check with the manufacturer. You'd have to see if that would be enough with a heat load analysis. They should last a long time, too. You might have to replace a thermostat along the way, but not the heating mat.
  3. like Jim said, it saves energy. Whatever you'll read about radiant heat is true in terms of allowing you to have cooler air and still feel warm, because walls, floors, furniture and objects are warmer than if your heating system made the air hot first. Warm air rises, but heated floors keep more warmth down at ankle level longer, so heat is more uniform throughout your living space. Like in many big concrete buildings.

    There is no disadvantage to underfloor heating except the added complexity and time to install it. A DIY has that time and ability, not a home builder who needs to get the trades in and out and can't wait. To install electric cables you need extra days, to lay them down and to cement them in a bit of thinset.

    Cables don't burn themselves out; the current is low. It is possible to locate an open circuit under tiles, break that one tile and repair cables. Rarely done. Cables are like toaster filaments that get only slightly hot. Even electric baseboard heaters almost never need repair or replacement, and they have very hot filaments.

    The heat is less than air heating; no bacteria or molds grow "more" because of this gentle distributed heat. Besides, your floors won't be continuously wet or dark either, and molds and bacteria need warmth, h2O, and not too much light while they are getting growing; so no, warm floors do not cause mold.

    There is no brand/model which is the best underfloor heating since the actual cable itself is quite simple. Getting the best answers to your questions, the best service, is often a deciding factor. The cable itself is not.

    david
  4. leejosepho

    leejosepho DIY scratch-pad engineer

    If you are accustomed to enjoying a burst of warm air when the conventional furnace comes on, it might take a little while to get used to first having your feet slowly warmed while waiting yet a little longer to feel an overall sense of comfort after coming in from the cold.

    Connections and fittings should be strategically placed, and it could be a good idea to keep a little extra tile or flooring stashed away just in case a minor repair might some day be needed.

    For electric wire, go with the heavy stuff used for casting into concrete, and either with wire or with pipe, make sure everyone clearly understands it is *never* okay to later drill a hole or to drive a nail or screw or anything else into the floor without first consulting the detailed "map" that was made at the time of system installation.
  5. I like the forced air..

    I like the forced air ........

    It seems simpler to operate and of course
    you share the duct work with the ac unit...



    I lived in a home as a child that had the boiler and the
    heat fin type radiators on the outside walls...

    yes it was nice, but my dad always had an extra 2 or 3

    Bell and Gossett pumps ready and primed .for when the darn thing would start troubles.and break down....

    .....Usually at X-mas...

    you have to like fooling with the darn things all the time





    he was a very handy fellow and I think he
    looked at the whole process of constantly working on it
    as a challenge to his manhood..in front of the family
    or something like that.......


    MAN against the boiler... and he was not going to be beaten..


    finally after about 35 years of messing and fiddiling
    with the thing all the time he tore it all out and put
    in the duct work in the crawl space and installed a
    forced air unit...


    the boler finally beat him
    Last edited by a moderator: Jun 22, 2007
  6. as houses become better built, from one decade to the next, they become more and more airtight so people rely less and less on air leaking in from the outside to give them their fresh air. If all doors and windows got taped / sealed shut tight, most houses would leak a lot of air through the door frames, moldings, switchboxes and floor boards. When a little wind blows, huge pressure differences force air in wall cavities to come through those opening as outside air is forced in through brick or siding and sucked out on the other side of the building. In winter you want to keep subfreezing air from coming in, and in summer you want to keep moist hot air from coming in. It's worse when the air has high humidity, relative (RH) to its carrying capacity. It's still bad when hot desert air comes in or cold dry air.

    Once you get an airtight envelope, you now need a plan to manage your indoor air. Indoor Air Quality (IAQ) is key to comfort; a million things you don't want to breathe so you won't give your body extra work eliminating what you have inhaled. Dust mite excrement, offgases and more.

    Heat stored in "mass" is felt as comfortable, up to a point (let's call that warmth); cold objects are felt as uncomfortable; a cold structure is felt as uncomfortable. The ASHRAE has defined heat "comfort" in terms of the temperature felt at ankle height and at head height, and the difference in the two readings. Cold floors and walls make less comfort.

    When air alone is heated, its heat is absorbed by the structure, but slowly and never as much as the air temperature. In winter, walls and floors are still cool when air is warm. The sensation it gives is that winter is coming in through the walls. Go to the big picture window or bow window in wintertime, sit there for an hour, and you will feel cold all over. When objects are warm and the warmth is spread out uniformly everwhere, nobody feels the sensation that winter is "right there" right in the structure. Warmth spread out radiant heat. Electric heat cables, or hot water pipes. Old fashioned radiators can be nice, but they can be uncomfortable too because the heat they give off is concentrated so high in one object that that object is too hot to touch and everybody "knows" it, they avoid it. (BTW, millions of hot water radiators in a million houses, don't require Dad to work all the time adjusting or fixing things.)

    Heating air forced to circulate distributes dust and indoor contaminants; it also does not ensure heat comfort as defined by the ASHRAE. Air warmed up will rise above other air not warmed, so heat rises when it is "in air". Heat does not rise in any other circumstance. Heat does not rise. It radiates, in all directions. The sun sends its heat in all directions, not "up". A warm object sends its heat in all directions. Only hot or warm air rises; this causes the top half of a room to be warmer than the bottom half and it does not warm the floor so your feet and ankles always feel cold. Not comfort.

    Heating applied internally to the structure at the coldest points (junction of floor and wall) does not force dust and indoor contaminants to become airborne. It provides warmth (not too high for comfort) at the places where cold is greatest in winter.

    -David
    p.s. ASHRAE is American Society of Heating, Refrigerating and Air-Conditioning Engineers www.ashrae.org/
    http://en.wikipedia.org/wiki/ASHRAE
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