Underfloor Heating efficiency.

Discussion in 'Plumbers' Talk' started by PlumbyGas, Jun 11, 2020.

  1. PlumbyGas

    PlumbyGas Member

    Afternoon all, just a quick one.

    Got a renovation on atm and got collared by the architect to go over the floor and ufh and all the gear had turned up.
    Floor in existing house is suspended floor, batterned, 100mm PIR insulation, UFH pipes and biscuit screed over the top.

    What peaked me was the full floor covering which will 18mm T&G chipboard, 6mm concrete board, 10mm tiles with adhesive. I call that about 38mm of build up mix materials.

    What is your opinions on the effectiveness of the UFH?

    Will these materials have a serious detrimental effect on the heat output?

    And please dont come with "it's not your house just do it answer"

    Cheers
    Plumby
     
  2. Dave does Gas

    Dave does Gas Screwfix Select

    Best thing I can sugest and its what I always do is send in the architects drawings to an UFH company with all the specs and they do the calculations and give you back a nice diagram of exactly how and where to lay it along with all the materials required.
    By doing that the customer has no comeback particularly if he or she is involed in the design.

    As to your question sorry cant give you a difinitive answer but Im sure someone will soon come along with a UFH heatloss calculator.
     
  3. Mike58

    Mike58 Screwfix Select

    It will take an age to heat up. I have UFH with 18mm ply in two rooms and that is OK. The bathroom has 18mm Hardie plus 10mm tiles - it takes a while but does finally get there and works well. The lounge is currently 4 or 6mm ply only and that does get warm but I know when change it to 14mm engineered there will be a delay.

    The build up you give is way too much, yes once heated it will stay warm but getting it there could be a couple of hours. Once there the heat output will be lower than expected as the surface temperature will be quite a way below the water temp rather than the usual gradient.

    Make teh customer aware and ask the to confirm exactly what you are to do - ensure no comeback on you when they find it is a slow cool system.
     
  4. rogerk101

    rogerk101 Screwfix Select

    No. I've installed 27mm engineered floorboards over UFH and it's been fine. I've installed fitted carpets with high density underlay over UFH and it's been fine. It doesn't affect the efficiency one little bit. It just slows down the heat transfer a little, i.e. introduces, say, 15 minutes of thermal delay at most.
    If it's OK to bury the UHF pipes in 75mm of screed, which is then tiled with another 10mm of tiles, then it's OK to cover them with a few layers of timber.
     
  5. PlumbyGas

    PlumbyGas Member

    That's good to hear, that was my thought originally but second guessed myself with the "thermal mass" of screed etc, people supplying the system were no help, architect was as helpful as................ an architect then made the mistake of speaking with the only other plumber I know in this area, (guy still moleskins lead) got some profanity about UFH being rubbish.
    Then made the mistake of quickly googling it...........

    Then thought let's ask the fountain of knowledge that is the Screwfix Forum
     

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