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Underfloor Heating for a new Garden Room?

Discussion in 'Plumbing and Central Heating' started by efunc, 15 Aug 2019 at 3:16 AM.

  1. efunc

    efunc

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    Hi all,

    I'm building a small garden room and have only just begun to speculate what heating I should have. The room is only 2.2m x 3.2m and 2.2m high. We have laid a concrete slab and will be laying 75mm Kingspan foil faced PIR insulation and then 50mm screed. I originally thought I'd have a wall mounted convection heater or something for the colder months, but have just realised that an electric underfloor heating system might be an option because we haven't yet done the screed.

    My understanding is that at about 6.5m2 the power draw might be about 1.5 - 2kw. Is that about right? If so, kw for kw how efficient would a basic screeded system be in a room of this volume (about 15.5m3) compared to a convection heater of similar power. Does the underfloor system have obvious benefits of economy or warmth, or is it just neatness?

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    The walls will also use 75mm Kingspan and the roof 100mm. The windows are all double glazed naturally. Other than that I have no heating plans yet.

    Unfortunately I just bought laminate flooring today, and if I was to do underfloor heating I don't think that would be the ideal choice.

    Thank you for any advice!
     
    Last edited: 15 Aug 2019 at 3:21 AM
  2. muggles

    muggles

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    Electric UFH would be fitted after the screed, not before, so you can carry on and get that done.

    However I'd suggest you have a split-unit heat pump instead. It'll be cheaper to run and provides cooling in the summer as well as heating in the winter
     
  3. efunc

    efunc

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  4. Notch7

    Notch7

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    In screed cables are an option -although from discussions Ive had with underfloor heating companies, a heating cable on top of screed will heat the floor faster and heat the screed as a heat sink.

    However underfloorheating has a slow response time -ideal in a room that used 12hours a day, no good for occasional use.

    Also underfloor heating needs 100mm of floor insulation to be really efficient.

    If you are going to use it for long hours, underfloor heating produces a nice heat -could be pricey to run though.
     
  5. efunc

    efunc

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    Fair enough, that's a good point. It might only be used for a couple of hours here and there during the colder months, so maybe a more immediate/responsive system might be better. I'll continue investigating it further though as I'm really quite new to the concept. Maybe a more conventional heater combined with underfloor heating mats, like this: https://www.theunderfloorheatingsto...ating-mats/warmup-foil-underfloor-heating-kit

    Although it looks like they still need specialist insulation panels and stuff below the mats rather than just relying on the PIR.
     
  6. efunc

    efunc

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    I'm looking at ThermaSkirt-E aluminium skirting boards too now, but probably left this too late really as I need to settle on something tomorrow. It's impossible to find relative installation or running costs between the various options.

    Realistically how cheap could UFH matts be to install? I was enticed by 6.5m2 kits selling for around £200, but suspect that's the tip of the iceberg.
     
  7. muggles

    muggles

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    I still maintain a split unit heat pump is the best option
     
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  8. efunc

    efunc

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    hardly unobtrusive though
     
  9. dilalio

    dilalio

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    But it will get you to comfort levels much faster and with the added benefit of cooling in the summer.
    Unobtrusive! Function over form, my friend... Nature can be trained to obscure the outside kit.
    I know what I'd do :)
     
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  10. Notch7

    Notch7

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    Your electric bill ftom the underfloor heating wont unobtrusive either o_O
     
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  11. stem

    stem

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    When a building is unheated for long periods of time the concrete floor acts a 'thermal mass' and will settle at the ambient temperature. So, when the air in the room is heated it wont have any noticeable effect on the floor temperature for several hours.

    In your case, just for occasional use, I would go with a 3kW electric wall mounted heater that can operate as a convector but has an optional fan boost to warm up the air temperature quickly ready for immediate use, in conjunction with a low wattage underfloor mat (ie that is designed just to warm the floor surface and not the entire room) just to take the chill off the floor.

    In the summer, if the building is kept shut and gets hot inside, the floor will continue to act as a thermal mass, so when the room is opened up and ventilated the air will cool, but the floor will take much longer to cool down.
     
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  12. efunc

    efunc

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    Thanks for all the advice. My main concern is really heating, not cooling. The garden room is shaded on most sides and only catches the sun in the morning so I suspect it'll be fairly comfortable in the summer. If it is ever hot enough we would simply open out all the doors, so A/C would not be of benefit, although a nice option to have. I'll look into it further, but in the meantime I got a quick quote for ThermaSkirt-E electric heated skirting. It's for 7m of skirting with Heat output designed at 1260 Watts for about £950. That's pretty steep as it doesn't include installation which I've heard is fiddly. I like the sound of the system though and if it was half the price I'd give it a go. I might have a look at the electric version of Thermodul Skirting Heating though in case that works out more reasonably, but will probably be more or less the same: http://www.skirtingboardheating.co.uk/skirting-heating-prices/

    The sensible thing might just be to go for a simple 3kW convection heater for now since I can't afford to throw masses of money at it. But if I paired it up with UFH mats as suggested, how much might this cost? Any recommended systems people have tried or links to check out?
     
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