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Disadvantages of Radiant Floor Heating

DannyDo Member Posts: 1
I've been seeing alot about the advantages of radiant heating, e.g., more even heating, more efficient, etc. but am having trouble figuring what the downside may be. Anyone?


  • Kevin O. Pulver_2
    Kevin O. Pulver_2 Member Posts: 87
    Not much downside but...

    the upfront cost. Some folks can't seem to see the value and won't budget for it when planning the dream home.
    Then they'll spend more on cable TV over the life of the mortgage than they would have to be comfortable; and pay higher fuel bills as rates rise every year.
    Depreciation on a car or two would probably cover a lot (or maybe all)of the cost also for a system that will appreciate in value for the life of the home.
    Secondly, the heat may take a few hours to ramp up first thing in the fall from a cold start, but outdoor reset helps that also.
    But if it's a shop you don't want to keep warm all the time, an infrared or scorched air system is more "instant" heat though they have several downsides compares to infloor radiant. And if you are constantly heating up your shop and letting it cool down, all the tools and power tools will sweat like crazy and tend to rust. I can't think of really any legitimate "downsides" to radiant. Kevin
  • Justin Gavin_5
    Justin Gavin_5 Member Posts: 26

    I agree with Kevin, The only downside I have ever seen in radiant was cost of operation in certain applications. In my area NE Wisconsin they are building 2500 sq ft homes with heat losses less than 40,000 btus. The infiltration rates are less than .20 ACH. They are going with R-26 walls, insulation of the basement of R7 Cont. and r-10 under the slab. The Ceilings are approaching R-44 as a standard. Exhaust is done smartly with dehumidistats.

    The standard furnaces installed are 95% variable speed furnaces. And now many contractors are incorporating Air Source Heat Pumps. These are very efficient systems compared to radiant.

    The mini-splits in Japan are currently testing units in WI that can heat efficiently to 5 degrees above zero and I have heard that they have units that can heat with an air source mini down to below zero.

    Those heat pump minis are pretty slick.

    Don't get me wrong, I love radiant, and I think that the comfort it provides is well worth the cost.

    What we do in alot of houses we deal with is put radiant in the basement, use a variable speed air handler for the upstairs with an air source heat pump for cooling and heating (down to 37 - 40 degrees)The key to an efficient installation is sizing a fan coil that can heat with the lowest possible temperatures, like the ones that Geothermal uses.

    Whatever the case scorched air really isn't as bad as it used to be but will never be what radiant was even 50 years ago.

    The old adage still stands, you get what you pay for.

    Remember comfort is King! Go Radiant!
  • the down side

    for me, since i like to put my feet on the coffee table when i'm on the couch, i lose the psychological effects of, warm feet/warm body. and if i have to raise the couch level temp, then the floor's too hot

    we've installed many heat pumps and mini-splits, and for the cost of elec vs propane, i leave my hp on, use my fireplace/furnace, and go to radiant last
  • Boilerpro_5
    Boilerpro_5 Member Posts: 407
    Radiant floor heating disadvantages

    There are a few others which I believe apply. The greatest is that radiant floor heat is greatly effected by floor coverings. If a system is designed to run with tile or hardwood, and you later install carpet or lots of throw rugs, you probably will have trouble heating the space, or at minimum have to rebalance the room with other rooms on the same zone and completely reset all the controls, especially outdoor reset controls. In this process you will also likely lose some system and boiler efficiency because everything has to run hotter.
    Next on my list would be the difficulty of room by room zoning, compared to other radiant systems. It can be done, but is much more work (more costly) and usually much more complicated. For other systems it is almost no work at all.
    Third is that while many radiant floor systems run at very low average temperatures, the temperature difference between the supply and return has to be very close when using typical pex installation methods in order to provide even heating of the floor. (Watts Onix tube can be designed using 20F drops for radiant floor) This temperature drop at design is usually 10F, and about 5F on a typical day for a home. Return water temperatures can run hotter with many radiant floor systems than with systems that allow greater temperature drops, more like 30F on design and 15F typical day. Greater return water temperature equal lower boiler efficiency for condensing boilers.
    Related to above, is when low temperature drops across a system are required, pumping power requirements can skyrocket, so you end up using lots of electricity, which is a very inefficient energy source. If I remember the formulas correctly, you need about 6 times the pumping power to move the same btu's at 10F drop versus 30F drop. Much of this depends on system design, but this is something to look out for.

    Radiant heating in general is inherently more efficient than air heating, even with the vast improvements in forced air. If you are looking for a great radiant system, you may want to look at radiant ceiling or walls. Or a very clean, no fuss, radiant system is to use radiant floor in those areas like baths, kitchens and tiled entries runnning wild on outdoor reset and then use radiant panel with Thermostatic radiator valves for all the other spaces. Floor coverings are a non issue, modulating room by room temp control is provided, and installation incredibly simple. In addition this system can be designed to run at 30F temperature drops and more to keep pumping power to a minimum and return temps to a condensing boiler low. And, the system can respond quickly to changes in heating needs (ie high solar gains, lots of company, cooking, etc)

    While radiant floor is the most comfortable system in my opine for places where heating loads are very steady, there are others systems that approach its comfort, provide other benefits, and are much less costly to install.


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