Re: Zoned Heating Control

["rb_ziggy" <rb.lists@xxxxxxxxxxxx>]

Chris

Not sure I quite follow your reasoning on the first paragraph.  I'm
pretty sure it's the temperature gradient (for a constant resistance)
that is the absolute determinant for the rate of heat transfer.  The
"rate of heat supply" has nothing to do with it.  (Consider the
case
when there is no gradient, it doesn't matter how much energy is pushed
through the slab in terms of volume of water, no heat will be
transferred).  As the gradient tends to zero, so does the rate of
transfer.

When there is more resistance, the rate of transfer is, of course,
reduced and it slows the warming of the cold side (i.e. it takes
longer for the gradient to reduce).

Essentially, all that means is that the more insulation you have, the
longer it takes to warm up (you experience greater thermal lag), so no
great surprise there then, ;-)  Raising the supply side water temp can
compensate for this but in the real world the problem is first, more
overrun (room heats up more than you wanted it to due to the residual
energy in the slab) and, second,  you go outside the sensible
boundaries of the materials.

In reality, for normal floor coverings, these things seem to make
little difference, underfloor heating is just very subtle. You barely
notice it as the house tends temperatures are constant (no hot spots
near rads or cold ones in the corners).

I hope that makes some kind of sense.  In reality it just works in my
experience.

On the other points:

- Loose floating does need an expansion area - usually under the
skirting.  I can see it being problematic if you don't want
skirting!!! I did see other systems where wooden battens are laid into
the screed and well seasoned t&g planks are nailed down onto that.  I
took one look at that and thought no-way was I going to find someone
who could lay battens into wet screed and get it flat.  A more
realistic system is to stick the engineered boards to the screed.
There is a special adhesive (sikabond???) that is designed for exactly
this over UF.  I looked at this closely and it's certainly possible
but it was a lot more expensive (just for the glue) and might be more
of a pro job.  IIRC this system still needs some expansion gaps at the
edges - at the end of the day, wood moves.  I'd love to find out how
those no-skirting floors are done - they do look great.

- A friend had an old parquet floor glued down.  Flooded and the floor
rose up in a dome about 12-18 inches high - didn't go back down
either.  But that was the least of his worries!

- polished screed - interesting. Add an interesting aggregate perhaps...

- Epoxy paint - interesting - garage floor???

- Lino - I fancied this but, guess what, its a great insulator and one
of the few finishes that the UF guys didn't recommend (really).  (I
wondered if it might get soft if it was warmed???)

Please do that the last few with a pinch of salt. Good luck.

--- In ukha_d@xxxxxxx, Chris Hunter <cjhunter@...> wrote:
>
> Richard -
>
> thanks ... interesting ...
>
> rather than temperature gradient, I guess it'll be rate of heat
> supply, that would be the constant, for a given room, with a higher
> temperature gradient between UFH pipe & air in the room being
needed
> to drive the heat through if there's more resistance, because of
> carpet or underlay, say ... and the higher temperature in the pipes
> that that would need would lead to some loss of efficiency, thanks to
> greater heat losses upstream from the UFH and basic thermodynamics
> (small temperature differences being more efficient in any
> thermodynamic / heat-cycle, IIRC) ...
>
> 'must say, I'm edgy about loose-floating the wooden covering &
> leaving a gap at the edge .... noise issues & what happens if
there's
> a flood !   Plus, we intend not having skirting boards !
>
> when we started our build, we had floor-grade hardboard on our list
> of options ... didn't sound a good idea, until I got a sample of the
> material ... it's still an option (suitably sealed) !
>
> 'wonder if it would be possible to leave the screed (anhydrous)
> uncovered ('might have to be sealed, I guess) ... or if an epoxy
> paint could be good ??
>
> if it was up to me, I think I'd go for welded linoleum, but 'wife
> wants wood !
>
> Chris
>
>
>
> On 29 Apr 2007, at 09:13, rb_ziggy wrote:
>
> > Bit of a gap - been away since your post!
> >
> > I wouldn't worry about the underlay. All these 'engineered'
wooden
> > floors work this way.  The planks are glued/locked together and
the
> > whole floor 'floats' loose on the screed.  This is what allows it
to
> > expand and contract without self destructing.  As long as the
whole
> > floor is subject to the same conditions (and it will be with UF)
then
> > there are no problems with differential expansion (i.e caused by
damp
> > one side and dry the other).
> >
> > I think the underlay does two things, it reduces noise (as stated
> > before) and it can (if you use the thick stuff) give a bit more
> > insulation to the slab.  You don't need the latter in a
under-slab
> > insulated house so just go for the 2-3mm underlay.
> >
> > It doesn't need any additional calculations / pipe as such.
(Adding
> > more pipe running at a lower temperature is actually a waste of
money
> > as it's the temperature gradient that is the determining factor.)
> > From what I remember, the wood + underlay creates no more of a
thermal
> > barrier than carpet. The company supplying can easily take these
> > factors into account when they design the pipe layout.  Most
supply
> > you with a specific piping layout on your plans.
> >
> > With underlay, it doesnt feel markedly 'softer' - just like a
'normal'
> > (slightly 'sprung'???) wood floor.  But it's a lot less hard than
> > ceramic tiles.
> >
> > We something like 120m2 of engineered wood flooring over uf and
it
> > works flawlessly for over 5 years.
> >
> > Richard
> >
> > --- In ukha_d@xxxxxxx, Chris Hunter <cjhunter@> wrote:
> >>
> >> Underlay ???   'hadn't thought of that !
> >>
> >> I imagined it would be glued to the screed, rather than laid
> >> loose ... interlocked, presumably, but loose ... ?
> >>
> >> which seems odd, because ceramic tiles wouldn't be laid
loose,
> >> surely, so glues must be available ... ?
> >>
> >> 'wonder how much hotter must the water be to cope with this
... maybe
> >> it's a specially conductive underlay ... maybe doubling the
pipe
> >> would compensate (IIRC Ian's used more pipe, to run cooler,
so might
> >> work) ... ?
> >>
> >> being softer underfoot might be good, of course, but it
rather puts
> >> me off the idea !
> >>
> >> Chris
> >>
> >>
> >>
> >>
> >> On 19 Apr 2007, at 01:10, rb_ziggy wrote:
> >>
> >>> We have a Kahrs 'engineered' (i.e. laminated not
laminate) wood
> >>> floor
> >>> throughout the ground floor.  Absolutely no probs with UF
in over 5
> >>> years.  Works fine.
> >>>
> >>> But as Nigel says, don't go for the thick (i.e.
insulating)
> >>> underlay,
> >>> that is rather counter-productive.  (N.B. do use underlay
though, a
> >>> friend laid the same floating flooring without and it
sounded like a
> >>> drum when the kids ran around).
> >>
> >>
> >>
> >> [Non-text portions of this message have been removed]
> >>
> >
> >
> >
> >
> >
> >
> >
>