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Heating and cooling: First floor UFH - is it necessary?

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  1.  
    • CommentAuthormaxelaine
    • CommentTimeNov 29th 2015
     
    Thanks to all who've contributed to my other threads, it's been really valuable.

    So, in a 90sqm floor area house, first floor lounge, open plan on both floors, stairs opening into lounge, very well insulated ( yearly space heating reqmnt about 2,500kWh, according to the SAP), with MVHR, do we need UFH on the first floor?

    Our designer says she's not a heating engineer. Her recommended heating engineer says we do, "without it, when the temp is below 0C, the MVHR will be constantly cooling the 1st floor and heat migration from the GF will be inadequate", which I don't understand.
  2.  
    I don't understand that either! Whether 'heat migration from the GF will be inadequate', it depends on the input. Effectively if you have no heat emitters to the FF you are relying on the GF heat emitters to put out enough heat to heat the entire GF and FF volume. If they can do that, fine. If not, supplementary heat is called for.

    As to the losses via MVHR, obviously it would have to be more than 100% efficient not to lose some heat, but I am not sure it would *feel* to be 'constantly cooling', especially as extract will normally be in the wet room(s) only, and closed doors may reduce the extent to which the rest of the FF area is cooled. That is not particularly scientific, since cooling of any part will eventually cool the whole, but I stress that in terms of 'feel' (comfort) the result may *feel* different.
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 29th 2015 edited
     
    The 2,500 kWh/year does not tell us that much.
    Is there a monthly/weekly breakdown of figures.

    Assuming that you expect to have some sort of formal heating system installed, what are the alternatives?

    I have storage heaters on the ground floor, and there were electric panel heaters upstairs. I removed these and just use a fan heater if I need to.

    I have considered getting a small Air to Air heat pump. This would heat all my house except the kitchen as long as doors where left open (I have open plan with stairs in the living room, I hate it), but they are not pretty or quiet.
    My house is about half the size of yours.

    Our old mate, Jeremy Harris, does not have heating upstairs in his low energy house. He does not have a problem and his place is only a little bigger than yours.
    Most of the time his ground floor UFH just moves heat around to even out the temperature.
    Read all about it here:
    http://www.ebuild.co.uk/blog/12/entry-99-in-the-beginning/

    It is a long read.
    • CommentAuthormaxelaine
    • CommentTimeNov 29th 2015
     
    From box 98 of the SAP, peak monthly heat requirement is 600kWh in december, and as someone on here advised, taking box 39 (heat transfer coefficient (W/K)) and multiplying by, say, 24 (minus 1 to plus 23), gives an estimated maximum heat load of 2.5kW.

    I'll have an ASHP (prob. 5kW max) to run GF UFH, and to get the DHW up to 40C-ish (with some yet-to-be-decided way of upping that to usable temperature).

    Steamy - my total floor area is 90sqm - i.e. footprint about half that - is yours really half that size? - ours seems small (but we've got the budget we've got),
    • CommentAuthorgyrogear
    • CommentTimeNov 29th 2015
     
    Depending on your layout, you could perhaps use a whole-house fan, to circulate air between the two floors...

    gg
    •  
      CommentAuthorSteamyTea
    • CommentTimeNov 29th 2015
     
    Yes my place is really half the size of yours. You never get used to a small house. There used to be 4 adults two doors from me. Out at moment watching big waves, but have a look at some small A2AHPs good CoP and dirt cheap.
    • CommentAuthorringi
    • CommentTimeNov 29th 2015
     
    => first floor lounge

    I assume the bedrooms are on the ground floor, if so remember people often like the bedrooms cooler then the living room.

    You could put one fan operated “radiator” on the 1st floor, running of your ASHP, or at least install the pipe work so you can add it later if needed.
  8.  
    Sorry, yeah, missed the FF lounge bit! If, like me, you want to keep the bedrooms several degrees cooler than the main living spaces, you may have more of an issue!
    • CommentAuthorSprocket
    • CommentTimeNov 29th 2015
     
    I was instinctively thinking NO to upstairs UFH.
    But I too had missed that important detail of bedrooms downstairs and lounge upstairs.
    If you do want to keep the bedrooms a little cooler than upstairs (would be my personal preference too) then UFH upstairs is a very non-intrusive (though admittedly expensive) way to do it.
    Personally I would be very wary of extra fans or ducting - I don't like that sort of complexity and it could lead to unwanted noise.
    It's only install costs presumably... running costs would not be affected because any extra heat you put in upstairs is heat you do not need to add downstairs. And the extra control of separate heating zones might be handy. Have you costed it?

    And a question for the panel... can an upstairs UFH with pexa pipe and metal heatspreaders work well from low temp ASHP output?... as well as a screeded UFH downstairs? Any tricky balancing required?

    And on the subject of balancing that, I also assume it would need a big buffer tank, since it does not have the thermal mass that the screed downstairs will have. Do you already have the buffer?

    Just some thoughts. Trying to get this setup clear in my head.
    • CommentAuthorgyrogear
    • CommentTimeNov 29th 2015
     
    If no to WHF, I'd go for a radiant wall

    gg
    • CommentAuthormaxelaine
    • CommentTimeNov 29th 2015 edited
     
    Thanks for all the interest - haven't digested comments yet, but downstairs is just kitchen & study, upstairs is lounge & bedroom.

    Steamy Tea - did look at AtoA HP, but want cosy kitchen floor.
    • CommentAuthorJonG
    • CommentTimeNov 29th 2015
     
    If the ufh is designed correctly you shouldn't feel a cosy floor.
    • CommentAuthorringi
    • CommentTimeNov 29th 2015
     
    I assume that the areas upstairs is larger then down stairs.

    (For a cosy kitchen floor, one option is electric UFH running on E7, depending on the kitchen size and assuming that you are also heating the air buy anther method, it may not cost much to run, and will give you the warm floor feeling in the morning.)
    • CommentAuthormaxelaine
    • CommentTimeNov 29th 2015
     
    GF & FF same areas.

    We shall be having UFH on the GF, run by ASHP.
    • CommentAuthortony
    • CommentTimeNov 29th 2015
     
    What are your u values and air tightness targets?
    • CommentAuthormaxelaine
    • CommentTimeNov 29th 2015
     
    Haven't got airtightness target, but to exceed BR.

    From SAP - Wall U = 0.18; GF U = 0.13; roof U = 0.11; window U = 0.96

    Total fabric heat loss (W/K, sigma area * U's) = 64.22
  17.  
    I would suggest that you design your MVHR ducting so that you have two separate branches for upstairs and down. You can then add a water borne duct heater to the upstairs branch and heat it that way.

    Other than a 900W electric duct heater in the ventilation we don't have any heat emitters upstairs and the house is comfortable at all times.

    Our house isn't a certified passive house our calculated heat demand according to PHPP is 22kWhrs/m^2/a but we haven't found any problem with heating upstairs via the ventilation. I was worried at first that it would be a problem so I bought some small cheap panel heaters but they are still in their boxes in the attic, perhaps in a tough winter they might be needed but we haven't come up against that yet.
    • CommentAuthorRex
    • CommentTimeNov 30th 2015
     
    Personally, I would suggest installing FF UFH. My T/F house is reasonably well insulated

    I was advised that with all the insulation, I would not need heating on the f/f but decided to put it in, as I can always turn it off. I have a fully, Warmcell insulated ceiling and the result is that not much heat escapes to the f/f. Yes, the f/f is a couple of degrees lower temp, but when the heating is off, the f/f definitely cools faster than the g/f.

    Additionally, as a t/f house, there is virtually zero thermal mass on the f/f and this definitely contributes to the faster cooling. I am very pleased that I did not follow the experts advice!
    •  
      CommentAuthordjh
    • CommentTimeNov 30th 2015
     
    Posted By: SteamyTeaOur old mate, Jeremy Harris, does not have heating upstairs in his low energy house. He does not have a problem and his place is only a little bigger than yours.

    Completely irrelevant as his house has a unique microclimate and is said to be much better insulated as well.
    •  
      CommentAuthordjh
    • CommentTimeNov 30th 2015
     
    Posted By: maxelaineHaven't got airtightness target, but to exceed BR.

    You need an airtightness target! There's absolutely no point in trying to build a well-insulated house without one. I'm afraid I'm back to my get a new designer suggestion again.
    •  
      CommentAuthordjh
    • CommentTimeNov 30th 2015
     
    Posted By: Chris P BaconI would suggest that you design your MVHR ducting so that you have two separate branches for upstairs and down. You can then add a water borne duct heater to the upstairs branch and heat it that way.

    That sounds like a reasonable idea. Possibly the heating should be limited to the living room and not the bedroom? It will depend on personal preference I suspect.
  22.  
    +1 on the airtightness, it should go hand in hand with minimizing cold bridges and maximizing insulation.

    Unfortunately it does go back to the fact that your designer is not doing a PHPP you have no proof that on paper at least your design will function as a low energy house.

    Part of the PHPP process will also confirm that you can indeed heat the house (or parts of it) via the ventilation system, it's not always possible primarily because air is a bad way to move heat around and you can't heat it over about 50C without getting a burning smell from dust in the airstream being burnt.
    • CommentAuthorSprocket
    • CommentTimeNov 30th 2015 edited
     
    Another +1 here on having a decent airtightness target.
    MVHR gets increasingly pointless+ineffective as air leakage increases.

    Air tightness losses can be comparable to insulation losses and having a number for each helps put things in perspective... so you can know you are spending money in the right place.

    Do you really need PHPP for this? Surely SAP should include allowance for ventilation?
    • CommentAuthorringi
    • CommentTimeNov 30th 2015
     
    Posted By: SprocketMVHR gets increasingly pointless+ineffective as air leakage increases.


    It depends on how much you like nice air in your home. MVHR is as much about quality of life then saving energy.
    •  
      CommentAuthorSteamyTea
    • CommentTimeDec 1st 2015
     
    Posted By: Rexvirtually zero thermal mass
    There is exactly zero 'thermal mass' :wink:
    What you will have is some mass with thermal properties that need calculating.

    I too missed that it was an upside down house, so will need some sort of heating.
    Having said that, it is the heating control what is really being discussed, the actual method of supply the heat is not that important.
    So how do you imagine each area/zone/room will be controlled?
    What you have to make sure is that the heating and the ventilation are not fighting each other for the majority of the time.
    • CommentAuthorSprocket
    • CommentTimeDec 1st 2015
     
    But ringi, surely you still want the nice air to all come through your MVHR so it can be warmed up?
    And beyond a certain level the heat losses to leakage are so big that the heat that MVHR can recover from the small amount of air going that route is barely significant... you might as well save yourself the money, not fit a MVHR, and open the window.
    • CommentAuthorringi
    • CommentTimeDec 1st 2015
     
    Sprocket,

    Windows can not be left open while we are out, my wife also does not like windows open at night as we live in a bungalow.

    The MVHR heats incoming air enough that we can not feel any drafts from the outlets. There is also little "stack effect" in a bungalow and the layout is not good for a PIV system. Within a hour of turning the MVHR on, my wife said she could no longer smell any dampness within a few days all our walls had dried out.

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