RE: Re: Underfloor heating...

["Timothy Morris" <timothy.morris@xxxxxxx>]

I'll echo Ben's comments. I'm on my second house with underfloor
heating, and things have moved on significantly in the last ten years.
All the loops (I've got 20 covering 85 sq metres) are fitted with flow
rate regulators and individual stats, so that each loop is balanced
according to the volume of room it has to heat. Latency is much
improved
too now. The plumber that fitted mine is now putting it in more and
more
now in 7 figure new builds in the South of England.

The system I've got comes from Polyplumb, and my control system is
desperately un-sophisticated, I've got 4 room stats! The plumber did
mention that I can fit wireless stats to it in the future that can be
controlled via PC if the need ever took me.

Tim

> -----Original Message-----
> From: bensbarn2001 [mailto:ben_wilkinson@xxxxxxx]
> Sent: 04 December 2002 17:56
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] Re: Underfloor heating...
> 
> Mark,
> 
> Sorry for the delay in replying but thought I'd contribute my
> experiences to this debate....
> 
> 
> > 1: Would you recommend it?
> Yes, absolutely.  It does have some issues with response time,
but I
> find these manageable.  As the house response time is pretty
much
> predictable, it lends itself very well to advanced forms of
control.
> Other thoughts on this:-
> Underfloor heating primarily works via radiant heat.  As this is
the
> type of heat which the human body is most sensitive to, you should
be
> able to run u/f heating systems at a degree or 2 lower than
> conventional systems.  Hence they should ultimately use less
power.
> Radiators are primarily convectors and the air currents which are
set
> up are a bit counter productive in terms of heating.
> 
> The response time varies depending on what substrate is being
> heated.  Some have mentioned heating plates.  These are
attached to
> floor boards in the case of a non-solid floor (such as wooden
joists)
> and therefore are mostly used upstairs.   They add to the
cost and
> complexity of installation, although I'm sure some mfrs have been
> working on that since I researched this.  Wood floors using
these
> plates don't have the response time issues associated with heating
a
> large concrete base.  Neither do they have the large thermal
mass
> when the system is turned off.
> 
> There is a limit to the temperature of the floor which is a
> compromise between comfort and heat output.  I think the
standard
> temperature is about 29deg C.  When U/f systems were around in
the
> 70s they got a lot of bad press because they were too warm.
> 
> At 29deg, the heat output from stone (or similar high thermal
> conductivity) is 100Watts/sqm.  It's 70W/sqm for wood and
somewhere
> between for carpet on a concrete floor.
> As you can't take the temperature too much above this, then this
> becomes the limiting feature for heat output, and so calculating
heat
> losses is critical to ensure that heat in will more than
compensate
> for heat out (generally done at -1 deg C).
> 
> Someone mentioned that putting the pipes closer together increases
> heat output.  That's not strictly true, as all it does is
reach
> operating temperature more quickly (ie decreases response time),
> although more heat will be generated during any ramp to normal
> operating temperature.
> 
> For solid floors and a wet system, the normal installation is to
> insulate the floor (minimum 25mm of celotex or similar), then put
> some grid or something to attach the pipes at 250-300mm centres),
> then put a layer of cement screed over the top.  Minimum
thickness
> for this is about 65mm.  Then you have to add the floor
covering.
> Wooden floors need attaching.  YOu can do this with glue,
although I
> used screws (shorter than distance to pipes).  So it's quite a
lot of
> depth all told.
> 
> I think others have described the electrical systems.
> 
> For my system I've got about 100mm of screed over the pipes, which
is
> a heck of a lot of concrete to heat, but once system has been used
> for a couple of days (eg at the moment, mine is on for about 2-3
> hours twice per day), the concrete never cools down.  It's very
nice
> when going walkabout in the middle of the night.  The house needs
to
> be reasonably insulated because of the inflexibility of heat
output.
> I haven't had the response time issues that Mark M (I think)
talked
> about.  I have individual control of each room and for some
reason
> the control system works very well as we're pretty much always
very
> close to the selected temperature.  It's always surprised me
that
> that's the case.
> 
> 
> > 2: Can it co-exist in a house that also has radiators in
other
> rooms.
> Yes.  The u/f manifolds (I have 2, with a total of 20 loops of
pipe)
> need special mixing valves to reduce the temperature (done by
mixing
> in return flow water).  Each manifold has a very big pump
because
> it's pumping water around a km or 2 of pipe.
> 
> U/F heating is particularly suited to condensing boilers as the
> return flow temp is so low which helps the condensor work
efficiently.
> 
> >
> > We have a lot of work to do in the sitting room, including
> replacing the
> > old, nasty carpet, with a wooden floor. Mary would like
individual
> > control of each room's temperature, and is happy to do this
with
> xAP /
> > Homevision... but would also like underfloor heating.
> >
> > Comments, suggestions, recommended suppliers?
> 
> Mine is from Wirsbo.  Very well established, reputable and
first-rate
> support.  I've had the system going for 5+ years with no
issues.
> Some suppliers change pipe regularly and I liked the 25 year pipe
> guarantee Wirsbo offered.  A lot of other suppliers have grown
up
> around the self-build industry and I would be very careful to
ensure
> they've got some pedigree before paying money.
> 
> That's it
> 
> Ben
> 
> 
> 
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