Underfloor heating and air con, or combined heating/cooling

Discussion in 'Engineers' Talk' started by BikerChris, Aug 1, 2019.


How to heat

Poll closed Aug 29, 2019.
  1. Combined unit

    0 vote(s)
  2. Underfloor and Air Con

    0 vote(s)
  1. BikerChris

    BikerChris Active Member

    Hey all

    Hope I have put this in the right place!

    I'm afraid its another outbuilding/office question that I have said about before, because I am doing it myself its going to be sips with usual cladding external, service bat internal + boarding. insulated roof etc.

    As the base will be new and I was going to do insulation then screed, heating / cooling wise should I:

    Use underfloor (electric) heating and wall mounted air con


    one box on the wall that will do both?

    It might be hassle to have 2 controllers for controlling the temp with the first option, but I dont like the idea of having hot air when I am in there. I have to say that my only experience is those small fan heaters.

    Any comments welcome.

  2. MGW

    MGW Screwfix Select

    This year is the first I have used an AC in the UK, in the past mainly window mounted units, but the big thing with any AC is noise. With proper building management the likes of the Myson iVector can do heating and cooling with either twin or single heat exchangers, and the fan speed is adjusted to control output, so if only a little heating or cooling required the fan is very slow, near silent, and when a lot of heating or cooling required one is more likely to accept the noise.

    But with the cheaper systems the noise can be OTT.

    Even the simple electronic TRV head makes some sound.

    But the next has to be time taken to get a room to temperature, the faster it does it, the less time it runs, so cheaper it works out, again with a fan assisted radiator it can heat a room in minutes, so geofencing is on the cards, worst has to be storage radiators closely followed with underfloor heating, to react fast a car heater type heat exchanger is wanted.

    However some buildings naturally store heat, and are slow to heat or cool what ever you do. So in real terms every building is different, when I worked on a large shop in Chester there was no heating, that came from all the lighting, it only had cooling.

    I would say forget electric under floor heating, the raychem is better than rest with auto compensating when some thing placed on the floor, but with limit of 29 degrees it will never be fast, so has to be on 24/7 which gets expensive.
    BikerChris likes this.
  3. Bob Rathbone

    Bob Rathbone Screwfix Select

    Go for a split air con system that will heat as well as cool.
    BikerChris likes this.
  4. BikerChris

    BikerChris Active Member

    Hi MGW,

    Thanks again for helping me out, real kind of you.

    Like you said, I am concerned about noise, I'm in a pretty quiet high density housing area and dont want to pee anyone off. I'm seeing a local place that does the combined units to see what sort of sound levels they make - of course the people selling are saying that their units are very quiet!

    It's going in a building that's fairly well insulated, so I'm hoping this will mean it won't need it too often but also that it won't cost me too much money to use. One thing I want is to not pay around £400 rent for an office anymore.

    The construction is going to be 144mm SIP with batten either side for weatherboarding / plasterboard.
    Hopefully it will warm up or cool down pretty quick, but I will probably play around with it and see which is cheaper - keeping a constant lower temp or turning it off and only on again when in use. I would definitely not have storage heaters, I don't know why but just don't like them (reminds me of bedsit days I guess) - but thanks for making up my mind on that one.

    Right, well thats a no to underfloor heating, thank you!

    Finally put the planning app in today, so it's a done deal, here's the floor plan. Cheers again mate, really appreciate it

    Attached Files:

  5. BikerChris

    BikerChris Active Member

    Cheers mate, good to have your input.
  6. MGW

    MGW Screwfix Select

    AC noise levels in an office not a problem, only in a bedroom and I had not realised office only. In a church the inferred heaters are very popular due to fast warm up times, but they are near impossible to control. So normal is a mixture.

    In the 1980's when I was involved with AC units a lot, some would reverse the motor and become heat pumps, but most simply had electric elements so although it seemed the heated the unit was really a wall mounted fan heater.
    BikerChris likes this.
  7. BikerChris

    BikerChris Active Member

    No worries at all @MGW , even so, I'd still like it to be quiet in there if poss, I'll see when I go there and have a look...or listen I mean. I'm not that fussed about a bit of a temp change, may be in a church they are tricky to control because of the height and size of space?

    yeah I'm not sure if it's just a glorified fan heater, I hope not cos that'll just give manky hot air. I might have to be in this thing for 12+ hours on certain days, so want it to be comfy - AND it will be the first time I can actually control the temp.

    This is a bit surplus info:

    Places I've rented in the past just aren't usable when its too hot, place I'm in at the moment gets to 35-40C which might be alright outside but not indoors. I'd put air con in but then that's my expense and its like giving someone money, unless I go thru the agro of taking it with me. That for just a week or may be 2 weeks of the year. Luckily the electric is included in rent, so in winter I just keep an oil filled radiator on and that does the job. Feel bad though having it on constantly but the rest of the building isn't heated properly.
  8. MGW

    MGW Screwfix Select

    Inferred in Church or garage is used because of fast warm up. They don't warm the air, they warm bodies in line of sight, how ever since they don't warm air, any thermostat that measures air temperature will not work, also as soon as switched off you feel cold.

    For first time in UK I have bought an AC, it is a portable unit which has a pipe to stick out of the window, however designed for sash window not hinged so it was a problem sealing the window to stop flies and of course heat coming in.

    My cure was to use the chimney, the hose is directed up the flue and sealed, however this would wet all the soot and cause it to fall, and moisture laden air is heavy, so would not readily go up the flue, however there was a bung and a pipe supplied to use when using as a dehumidifier, once that pipe was connected, the water ran into a bowl, and the drier air went up the flue no problem. So only down side is noise, the TV has to be turned up loud.

    As you say the AC is used for maybe 6 weeks of the year, not worth spending too much, think mine is really too small, from Lidi it's 650 watt and around 70 watt of that is the fans, so room around 22 foot by 10 foot, switch on AC and leave running great, but let room get hot, and not really man enough to cool it. In Algeria a portacabin was split into 3 with an AC in each room or 3 kW, OK it was the Sahara so 130 deg F in the shade, but only window was one in door, painted white, and well insulated. Hong Kong also had a 3 kW AC in my flat, and not big enough when cooking.

    However if it drops temperature from 30 to 25 deg C I can live with that. For your little office a portable should be fine, as long as you can seal pipe in window.
    BikerChris likes this.
  9. BikerChris

    BikerChris Active Member

    That makes sense about the Churches, never knew that.

    By chance I bought a portable AC unit as well, it's pretty good for small spaces that are fairly airtight and allow the outlet to go straight out of a sealed window. As I'm building something from scratch, I'm hoping not to have any ad-hoc stuff and do it as properly as I can afford. That's interesting about using the flue to get rid of the hot air, nice one - like you said though, they are bloody loud or mine is at least. It's the £250 that screwfix sell, that I got.

    Spot on though, 25C I'm happy with that for sure.
  10. JoeCampbell

    JoeCampbell New Member

    So what have you chosen? I'm also setting up my basement right now and can't decide yet. Underfloor heating sounds neat, but did you have problems with it (if you have it, ofc)? About AC. Last summer, the temperature overboard reached 36 degrees. It's almost impossible to work. I just bought an air conditioner. I haven't figured out a better one yet as to put it on the top shelf. Also, did you hear something about these guys https://www.spartamech.co.uk/? They were recommended to me, but maybe someone here used their services. Anyway, I need someone to set underfloor heating.
  11. BikerChris

    BikerChris Active Member

    I'm probably going for a split air con unit that does both, mind you, the slab is going in this or next week (yes very delayed lol!) and I've extended the slab for floor mounting the unit. I guess in your situation it depends on the size of the basement and if you have the head height to raise the floor and stick some insulation on the floor, then at the same time you might be able to get wet underfloor heating may be, if your boiler is up to the task? If you can make doe with your air con unit, so be it, but if it struggles you might wanna get an external one, only if you're not close to neighbours though (noise). That company you mentioned looks like it's based in Herefordshire which is far away from me, for you probably best to get a quote and go from there may be?
  12. MGW

    MGW Screwfix Select

    Around 1980 I fitted central heating in my new house, the Myson fan assisted radiator of that time had the option to run the fan in summer, however rarely used, the position and size of windows did not overheat the open plan house.

    Mothers old house with bay window, and this living room with a lot of glass is however very diffrent, however there are coating that can be applied to windows to reduce the suns effect, I will likely get some in the future, but also plan to fit better double glazed windows first.

    I am also considering a retractable cover like used on shops and caravans.
    BikerChris likes this.
  13. Jimbo

    Jimbo Screwfix Select

    Some of the Panasonic high-walls are getting SCOPs nudging 7. They will be sooo much cheaper to run than electric UFH and as said work much quicker. Outdoor unit will be almost silent with a small system like this.

    Another option would be wet UFH and a small air-to-water heat pump like this: Vaillant aroTHERM Plus Air Source Heat Pump 3.5kW 10037211 (directheatingsupplies.co.uk). This will definitely make the place more comfortable as you won't have cold feet and neither will you have a hot draught. It can also do cooling but you will need a fan-coil unit really and a carefully designed system to avoid condensation. It can also do cooling via the UFH but the effect is going to be very limited because of the need to keep the slab above the dew point.
  14. kiaora

    kiaora Guest

    i agree with above,
    with wet underfloor heating the low temperature they work at, is ideal for any solar or wind energy you can make, or the low temperature of the heat pump
    with a with a coefficient of performance of 4+ that's 4 times more kw of heat out for 1 kw in !
    and the underfloor heating is like the floor is a big heat store,
    i have 75mm screed on my insulated floor, works very well with 35c temperature water

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