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Heating and cooling: Infra red heating - floor and ceiling

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  1.  
    • CommentAuthorMiked2714
    • CommentTimeOct 5th 2016 edited
     
    I haven't seen any discussion for a while, just wondering if anyone has experience with electric far-infrared heating mats either in floor or maybe even ceiling. Seems too good to be true. I'm looking for a product to provide supplemental heating for both large and small rooms, where it's awkward to get an even heat from the main wet central heating.
    • CommentAuthorFred56
    • CommentTimeOct 5th 2016
     
    If it's too good to be true, it isn't true. Daytime electricity is just under 16p per kWhr on my bills.
    • CommentAuthorMiked2714
    • CommentTimeOct 5th 2016
     
    Sorry, should have clarified, it would be heated by solar PV which would otherwise go to the grid.

    I'm really looking for comments from people who have practical experience of it.
    • CommentAuthorgyrogear
    • CommentTimeOct 5th 2016
     
    I am planning on installing one under a concrete staircase cubby - it is 2 m2 x 100 watts per m2.
    Comes with a thermostat control, so it is not delivering continuously...

    It will be installed by my electrician, with a timer so that it runs in off-peak only.

    I tested the idea using a halogen light, for 2 weeks, and the principle works...

    gg
    • CommentAuthorDarylP
    • CommentTimeOct 5th 2016
     
    @Miked2714, would you need space heating when the sun is shining....?:confused:
    • CommentAuthorgravelld
    • CommentTimeOct 5th 2016
     
    My thought too. Isn't IR heating for point of use? Can radiated energy be absorbed by a material for release later?

    Better to feed into a thermal store of some sort.
    • CommentAuthorMiked2714
    • CommentTimeOct 5th 2016
     
    Daryl. Well only partly, it's not going to be 100% solar, but we do have battery storage so most usage in morning and evening would be battery-powered. And even when it's sunny, there can still be a need to take the chill off, especially in rooms that don't get much solar radiation.

    One interest is how much "better" is IR-underfloor than conventional electric underfloor.

    I do get the point that gas is cheaper than electric, we are mostly gas-heated, but I like the theory that you can get better comfort at lower overall temperature with some IR.

    In the end I may just have a try at this on a small scale to see if it works. If it does then I will report back of course. I'll also contact the suppliers to see what they say.
    • CommentAuthortony
    • CommentTimeOct 5th 2016
     
    efficiency 100%, all the electricity turns into heat, this might sound good but....

    poor when compared with a heat pump where each kW of electricity produces 3.5kW of heat.
    • CommentAuthorbarney
    • CommentTimeOct 5th 2016
     
    You can get a quick estimate of the effect of IR from understanding comfort temperature.

    Basically, the comfort temperature is approximately the sum of 0.5 x the mean radiant temperature and 0.5 x the air temperature

    It's the increased radiant component that allows lower air temperatures to maintain comfort (and lower air temperatures provide a degree of "freshness" )

    Work out the radiant temperature of the system and go from there

    Regards

    barney
    • CommentAuthorEd Davies
    • CommentTimeOct 5th 2016
     
    Posted By: Miked2714One interest is how much "better" is IR-underfloor than conventional electric underfloor.
    Any idea how they differ? My understanding is that the wall mounted IR heaters run at a reasonably high temperature, have a high emissivity and only one surface in contact with the air so put out a larger proportion of IR (vs convection and conduction) than conventional “radiators” but I don't see how that sort of distinction can be made with underfloor heating.
    • CommentAuthorCWatters
    • CommentTimeOct 5th 2016
     
    IR heaters are good for situations where you can stand in front of them and can't easily heat the whole room. Eg places like garages and workshops where cars are going in and out. I suppose they may also work ok you are immobile (eg sat in a chair). Even then you might feel warm on one side and cold on the other.

    The problem is that heating the whole room feels so much more comfortable and for that it makes little difference what you use because the energy required depends mainly on how well it's insulated. As others have said...all conventional electric heaters are 100% efficient so running costs should be about the same if the level of comfort is the same. The exception being heat pumps which have an inherent advantage.
    •  
      CommentAuthorfostertom
    • CommentTimeOct 6th 2016 edited
     
    AFAICS, 'far IR' vs 'conventional' electric heating mats is meaningless when embedded in wall, floor or ceiling.

    It doesn't matter what the unit's heat-output thing is doing, the only thing that matters is what wavelength IR the wall, floor or ceiling surface is emitting - and that will be entirely governed by the emissivity, colour(?) and temperature of the the wall, floor finish or ceiling surface, i.e. nothing that the embedded 'far IR' unit can influence.

    I'd guess that the only way that the wavelength of IR present, can escape from just being a function of emitting surface, is when you're directly exposed (through glass) to an incandescent electric element, which obviously can have its output wavelength controlled, like in a 'far IR' sauna box. Even then, as soon as that IR radiation is absorbed and re-emitted by all the room/box's surfaces, that re-emitted IR will again be a function of those surfaces.
    •  
      CommentAuthorSteamyTea
    • CommentTimeOct 6th 2016
     
    I see that many of these systems are sold with a controller. What does that controller sense, air temperature?
    • CommentAuthorEd Davies
    • CommentTimeOct 6th 2016
     
    I think the same as FT, above, but was wondering if I was missing something.
    • CommentAuthorbarney
    • CommentTimeOct 6th 2016
     
    It depends ST - cheap ones are basically a thermostat reacting to air temperature

    Better quality units are "black bulb" sensors that are reacting to IR

    Regards

    Barney
    • CommentAuthorsmudger
    • CommentTimeOct 9th 2016
     
    I installed some IR heated mirrors in bathroom as 'point of use' especially on cold summer days and supplements when heating is on but not necessarily when bathing. There isnt any residual heat to walls etc even when we initially left them on. Useful in shower / bathrooms as we have an unsteamed up mirror but wouldnt use anywhere else. Best way to divert excess PV is to hot water - this can be integrated to supplement your (lucky-you) mains gas fired ch system via an immersion?
  17.  
    Does IR not tend to heat simply the bit it hits?

    If I have one above me, do I not get a hot head and retain cold feet? If it points at my front, do I not retain a cold back? I have not done a scientific test of IR htg, but have been in the odd hall which has it, and my vague memory is getting baked in parts and cold in others, not wholly unlike 'portacabin syndrome' (with any form of heat), which overheats your head (because all the heat has risen to the top of the cabin) and freezes your feet.

    Does IR really give wholly comfortable full-body heat?

    Or do bits feel cold?

    Anyone got any sort of prolonged 1st-hand experience?

    Thanks!
  18.  
    .
    • CommentAuthorbarney
    • CommentTimeDec 14th 2016
     
    Well, we use an awful lot of heated and cooled radiant panels In hospitals as the bulk of the people are lying down in light clothing - so they work very well in conjunction with well positioned conventional radiators and of course a constant temperature air supply system

    They are also used in a lot of spaces that are more "conventional" day rooms, lounges, relatives rooms, etc - where they are comparable to your domestic "sitting room"

    Hot head, cold feet is a potential problem, but relatively easily controlled by the actual temperature of the emitter (and in the health care environment significantly influenced by the ventilation). The vent rates would be easily 6ACH for hygiene purposes - you'd never get that in a domestic setting

    Regards

    Barney

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