Is it OK to have underfloor heating as your primary heat source for a
room (I'm looking at installing it into my kitchen)?

If so, what type and output would I need to get? I'm only looking at
covering about 9 square metres.

TIA.

Is it OK to have underfloor heating as your primary heat source for a
room (I'm looking at installing it into my kitchen)?

Yes, it is fine as the primary heating, provided that the room is well
insulated. The output is limited, and can't heat a room on its own that is
poorly insulated.

If so, what type and output would I need to get? I'm only looking at
covering about 9 square metres.

Assuming you have wet central heating, the best method is to use PEX pipe
buried in the floor (concrete floor) or between the joists (wooden floor).
This is easier to retrofit to wooden floors, as the concrete will normally
need digging out to add insulation and pipework.

Christian.

Christian McArdle wrote:

Yes, it is fine as the primary heating, provided that the room is well
insulated. The output is limited, and can't heat a room on its own that is
poorly insulated.
Christian.

Thanks yet again Christian, is there anything you can't help with?

Can you suggest any cheap, but good systems?

Christian McArdle wrote:
Can you suggest any cheap, but good systems?

Well the cheapest method is just to buy lots of PEX pipe and some clips.
However, there are lots of companies that will sort you out with kits. For
recommendations, you will need to say what your existing floor construction
is.

One issue is that underfloor heating must be run at a much lower temperature
than normal central heating or hot water heating. This means that you must
also install a thermostatic mixing valve and pump for the underfloor system
(this can be shared amongst all underfloor systems within the house). This
is easy to do and not expensive, but you need somewhere accessible nearby to
install the valve and pump.

Christian.

I have a solid concrete floor which we are ripping up and going to
re-lay.

I have a solid concrete floor which we are ripping up and going to
re-lay.

You could try something like a Continental Solution 10 kit. Make sure,
whatever you choose, that the floor construction is appropriate before
laying any concrete.

http://www.discountedheating.co.uk/s...lution_10.html
http://www.continental-ufh.com

Christian.

"mkkbb" wrote in message
ups.com...
Is it OK to have underfloor heating as your primary heat source for a
room (I'm looking at installing it into my kitchen)?

If so, what type and output would I need to get? I'm only looking at
covering about 9 square metres.

A waste of time. Use a Myson Kickspace fan convector. It goes in the
kickspace under the units. All you see is a neat grill, chrome or many
other colours. Blows heat across your feet. You can even have a wall
thermostat on it to ensure the kitchen doesn't overheat. No long lag in
warm up, as it warms up very fast and heat is instantly gone when the fan is
off. With UFH in a kitchen the heat hangs around for hours, meaning you may
have to open windows wasting heat which you have paid for, when the oven is
put on adding heat to the kitchen.

On 14 Aug 2006 03:25:41 -0700 someone who may be "mkkbb"
wrote this:-

I have a solid concrete floor which we are ripping up and going to
re-lay.

In addition to operating the underfloor heating at a lower
temperature to radiators, so that people can stand on the floor,
underfloor heating also has different time characteristics. It can
be turned off earlier than radiators (because the floor provides
thermal storage) and will probably need to be turned on earlier.
Thus it should be on a separate time control, have a room thermostat
and ideally the pump and mixing valve should be arranged to
compensate for outside temperature. All this is no great hardship as
controllers are available to do all of this.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Christian McArdle wrote:
I have a solid concrete floor which we are ripping up and going to
re-lay.

You could try something like a Continental Solution 10 kit. Make sure,
whatever you choose, that the floor construction is appropriate before
laying any concrete.

http://www.discountedheating.co.uk/s...lution_10.html
http://www.continental-ufh.com

Christian.
If you really want to be warm, forget about underfloor heating.
Whenever I look at a these systems they invariably are used in
conjunction with other heaters and the owners just wont admit that they
are useless because they spent so much money putting them in.

Put a decent layer of insulation under the floor and leave it at that.

wrote:
If you really want to be warm, forget about underfloor heating.
Whenever I look at a these systems they invariably are used in
conjunction with other heaters and the owners just wont admit that they
are useless because they spent so much money putting them in.

IMHO - this is utter rubbish.

Pretty much our entire downstairs is UFH and is wonderful - gently warm
underfoot, invisible, economical and not expensive to install.

I'm yet to hear of anyone complain about a well-designed and installed
*wet* UFH system. Now *electric* is another matter....

Jon.

If you really want to be warm, forget about underfloor heating.
Whenever I look at a these systems they invariably are used in
conjunction with other heaters and the owners just wont admit that they
are useless because they spent so much money putting them in.

Certainly, the numbers suggest that unless the room is well insulated, the
total heat output will be insufficient. However, they have significant
advantages over other methods. In particular, they are very useful in rooms
with tiled floors, such as bathrooms and kitchens, as they enable you to use
the room without having to find shoes or slippers. They are also useful in
wetter rooms, as puddles of water will evaporate more readily. Finally, the
heating will be much quieter than the alternative, which in most kitchens
would be a fan convector, as wall space is too valuable to use for passively
convected radiators.

That said, the fan convector has a considerable advantage in terms of
rapidity of heating. I think the best solution for a kitchen is to actually
have both underfloor and fan convector. This gives the best of both worlds,
with warm feet, rapid response and high total heat output.

In my own kitchen, I have a fan convector (plus an absolutely tiny radiator
that was there already that couldn't heat a cupboard, let alone a kitchen).
This does provide very effective and rapid heating. However, I do miss
having a warm floor and it is a pain in winter having to find footwear for
every foray into the room, unless the heating has been on for hours.

Christian.

"Tournifreak" wrote in message
ps.com...

wrote:
If you really want to be warm, forget about underfloor heating.
Whenever I look at a these systems they invariably are used in
conjunction with other heaters and the owners just wont admit that they
are useless because they spent so much money putting them in.

IMHO - this is utter rubbish.

It isn't at all. UFH needs well thought out control to be effective. Many
installers (plumbers really not know too much about it) throw lots of
plastic pipe under the floors, thinking this will solve everything. It
doesn't.

Pretty much our entire downstairs is UFH and is wonderful - gently warm
underfoot, invisible, economical and not expensive to install.

I'm yet to hear of anyone complain about a well-designed and installed
*wet* UFH system. Now *electric* is another matter....

Jon.

"Christian McArdle" wrote in message
...
If you really want to be warm, forget about underfloor heating.
Whenever I look at a these systems they invariably are used in
conjunction with other heaters and the owners just wont admit that they
are useless because they spent so much money putting them in.

Certainly, the numbers suggest that unless the room is well insulated, the
total heat output will be insufficient. However, they have significant
advantages over other methods. In particular, they are very useful in
rooms
with tiled floors, such as bathrooms and kitchens, as they enable you to
use
the room without having to find shoes or slippers.

A new floor with lots of foam insulation under, and to the sides up to
screed level, forming a tray, will not be cold. The tiles will eventually
heat up with the heating system and not lose heat to the ground beneath.

Having UFH and a Myson convestor is expensive madness. A kitchen needs heat
instantly and to be able to stop heat instantly. A kitchen is the last
place UFH should be considered.

A new floor with lots of foam insulation under, and to the sides up to
screed level, forming a tray, will not be cold. The tiles will eventually
heat up with the heating system and not lose heat to the ground beneath.

The problem is that heat rises, so the floor is the last thing to warm up,
unless it forms part of the heating system itself, or there is a heated room
below it.

Christian.

Doctor Drivel wrote:



Having UFH and a Myson convestor is expensive madness. A kitchen needs
heat instantly and to be able to stop heat instantly. A kitchen is the
last place UFH should be considered.


Not if your spouse suffers from serious cramp in her feet as a
consequence of arthritis. Why do you suggest that a kitchen requires
instantaneous heat? We spend more waking hours in our kitchen and
breakfast room than in any other part of the house.

And the cats love the Myson Kickspace heater ;-)

Richard

Not if your spouse suffers from serious cramp in her feet as a
consequence of arthritis. Why do you suggest that a kitchen requires
instantaneous heat? We spend more waking hours in our kitchen and
breakfast room than in any other part of the house.

There is an advantage in having rapidly responding heat output in a kitchen.
This is because the kitchen can hold other considerable heat producing
devices, such as ovens, microwaves, washing machines and hobs. A responsive
system can rapidly shut down, whilst a slow acting system may overheat the
room.

This is why I think a composite system containing both fan convectors and a
low output underfloor system would work most effectively in a kitchen. It
is, however, I concede, not the cheapest option by a large marign.

Christian.

Interesting thoughts brought up. I think the underfloor option will
probably be too expensive for me, but I will definately look into the
fan heaters. Thanks everyone.

Interesting thoughts brought up. I think the underfloor option will
probably be too expensive for me, but I will definately look into the
fan heaters. Thanks everyone.

You can hedge your bets if you like. You can install the pipework, but not
fit the expensive manifolds/pump assemblies. Then, if you change your mind
later, you can complete the install. Once the floor is down, the opportunity
won't arise again!

BTW, the Myson Kickspace is very good. I have a 600 hydronic and it heats up
the kitchen very rapidly. It is best fitted on its own heating zone,
although this isn't essential. If you don't install a zone valve at all,
then balancing will be critical, or it will short circuit your heating
system even when off. A room stat is absolutely essential, too. They are so
powerful, the room would rapidly overheat without one.

Christian.

"Richard" wrote in message
...
Doctor Drivel wrote:



Having UFH and a Myson convector is expensive madness. A kitchen needs
heat instantly and to be able to stop heat instantly. A kitchen is the
last place UFH should be considered.

Not if your spouse suffers from serious cramp in her feet as a consequence
of arthritis.

That is not the norm and a special circumstance. Also the Myson blow warm
air across the floor, so beneficial in your case.

Why do you suggest that a kitchen requires instantaneous heat?

As the cooking appliance can generate heat quite quickly and the heating
should be capable of being off immediately. The Myson will do this.

We spend more waking hours in our kitchen and breakfast room than in any
other part of the house.

And the cats love the Myson Kickspace heater ;-)

Richard

You got itn then.

Doctor Drivel wrote:




You got itn then.


Almost! The Myson is the only heat source (apart from hob and oven as
you so rightly observe). I had sorted a supplier of electric UFH and
bought the tiles when spouse decided that it would be a good idea to
rebuild the back of the house - removing and replacing the breakfast
room in the process. sigh So we _will_ have Myson + electric UHF
in the kitchen and breakfast room when everything settles plus UHF in
the new sitting room (possibly wet as a new slab will be required for
what is effectively a new extension) supported by a wood burner.

Richard

Christian McArdle wrote:



There is an advantage in having rapidly responding heat output in a kitchen.
This is because the kitchen can hold other considerable heat producing
devices, such as ovens, microwaves, washing machines and hobs. A responsive
system can rapidly shut down, whilst a slow acting system may overheat the
room.

This is why I think a composite system containing both fan convectors and a
low output underfloor system would work most effectively in a kitchen. It
is, however, I concede, not the cheapest option by a large marign.

Christian.



Hi Christian

Sorry, I intended to convey in my posting that I think a composite
system is sensible, but wanted to see why Dr D doesn't.

Richard

On Mon, 14 Aug 2006 01:15:12 -0700, mkkbb wrote:

Is it OK to have underfloor heating as your primary heat source for a
room (I'm looking at installing it into my kitchen)?

If so, what type and output would I need to get? I'm only looking at
covering about 9 square metres.

I've done a cheap'n'cheerful one in my kitchen. I had to take up the
(suspended) floor anyway so I insulated between the joists with rockwool
laid on garden netting slung over them, then ran 15mm polybutylene pipe
(Hep2O or equivalent) up and down between the joists suspended just below
the floor level by tiewrapping it to lengths of screwfix builders band
fixed across the top of the joists. Then I laid the new plywood floor and
tiled on top of the wood. The pipe is connected directly into the CH
circuit via a TRV under the floor set to open when the air temperature in
the unheated void below the floor drops to a coldish temperature (I forget
what). In practice the heating is a bit patchy with some areas
feeling quite warm and some cool (to bare feet or hands) but generally the
room is a comfortable temperature in all but the coldest weather.

If I were doing one professionally I'd calculate the heatloss of the room
using the standard method (U values of surfaces + ventilation losses) and
compare the heat output available from any of the construction methods for
UFH for which figures are available to see if it's possible to match
the heatloss. If the room has a large heatloss e.g poorly insulated
external walls and windows and a small floor area (allowing for the area
taken up by units etc) it may not be possible to entirely heat the room
with UFH. In this case extra heating from a radiator or kickspace heater
may be required in the coldest weater. (Depending on how much of a
shortfall there is it may be acceptable to supplement the UFH with an
electric fan heater in cold weater, rather than going to the expense of a
kickspace heater on the central heating.)

Doing it 'properly' one should also fit a separate pumped
thermostatically mixed supply to the UFH so that it runs at a lower
temperature than the main CH circuit.

On Mon, 14 Aug 2006 13:12:59 +0100, Christian McArdle wrote:

Not if your spouse suffers from serious cramp in her feet as a
consequence of arthritis. Why do you suggest that a kitchen requires
instantaneous heat? We spend more waking hours in our kitchen and
breakfast room than in any other part of the house.

There is an advantage in having rapidly responding heat output in a kitchen.
This is because the kitchen can hold other considerable heat producing
devices, such as ovens, microwaves, washing machines and hobs. A responsive
system can rapidly shut down, whilst a slow acting system may overheat the
room.

Ovens and hobs (used intensively) yes, but microwaves and washing
machines? These should produce a negligible contribution to space heating.

Also because UFH produces radiant heat whereas ovens & hobs heat the air I
wonder whether the excess heating would subjectively feel as much as if
the central heating were an unregulated radiator or fan heater producing
the same comfort levels. I think an argument could be made for UFH as
primary heating in a kitchen because of its greater efficiency in areas of
more frequent air changes (such as kitchens and bathrooms).

mkkbb wrote:
Is it OK to have underfloor heating as your primary heat source for a
room (I'm looking at installing it into my kitchen)?

Definitely if the insulation is up to snuff and teh density of pipe is
great enough to match the heatloss.


If so, what type and output would I need to get? I'm only looking at
covering about 9 square metres.


between 50W/sq meter and 200W/sq meter depending on room insulatuon and
heatloss.

So between 450W and 2KW...

You MUST insulate the floor though, or it will be bearer 400W/sq meter,
with you providing a nice little soil heater for the worms..


TIA.

Christian McArdle wrote:
Is it OK to have underfloor heating as your primary heat source for a
room (I'm looking at installing it into my kitchen)?

Yes, it is fine as the primary heating, provided that the room is well
insulated. The output is limited, and can't heat a room on its own that is
poorly insulated.

It can, but a floor in direct contact with a cold bit of earth is only
about 25% efficient..it costs a fortyne and leasds to very heavy pipe
density.

If so, what type and output would I need to get? I'm only looking at
covering about 9 square metres.

Assuming you have wet central heating, the best method is to use PEX pipe
buried in the floor (concrete floor) or between the joists (wooden floor).
This is easier to retrofit to wooden floors, as the concrete will normally
need digging out to add insulation and pipework.


Yup.

www.polyplumb.co.uk has some data that I used.

I went for 200mm pipe spacing IIRC.

I think that was around 50W/square meter. Its enough - just - in the
very coldest weather. Frankly 100mm spacing might be better in all but
modern insulated rooms, and then simply use a thermostat to limit the
temp rise.


Christian.

Christian McArdle wrote:
Can you suggest any cheap, but good systems?

Well the cheapest method is just to buy lots of PEX pipe and some clips.
However, there are lots of companies that will sort you out with kits. For
recommendations, you will need to say what your existing floor construction
is.

One issue is that underfloor heating must be run at a much lower temperature
than normal central heating or hot water heating. This means that you must
also install a thermostatic mixing valve and pump for the underfloor system
(this can be shared amongst all underfloor systems within the house). This
is easy to do and not expensive, but you need somewhere accessible nearby to
install the valve and pump.

Yup. Not recommened to run pipe-in-screed much over 45C whereas CH can
be up to 70C IIRC.

Simply restricting the flow ain't good enough - you just get high entry
and low exit temps.

You need an aux pump, thermo mixing valve and a relay, cos that pump
will be running (and need to run) independently of the main CH pump.

Christian.

mkkbb wrote:
Christian McArdle wrote:
Can you suggest any cheap, but good systems?
Well the cheapest method is just to buy lots of PEX pipe and some clips.
However, there are lots of companies that will sort you out with kits. For
recommendations, you will need to say what your existing floor construction
is.

One issue is that underfloor heating must be run at a much lower temperature
than normal central heating or hot water heating. This means that you must
also install a thermostatic mixing valve and pump for the underfloor system
(this can be shared amongst all underfloor systems within the house). This
is easy to do and not expensive, but you need somewhere accessible nearby to
install the valve and pump.

Christian.

I have a solid concrete floor which we are ripping up and going to
re-lay.


Stout lad!

You need AT LEAST 50mm, and the more the better, isnulation in it
somewhere. I used blue styrene foam. Celotex type is even better, though
not as strong. On a total green field type install its cheaper to use
e,.g 75mm blue than 50mm celotex..

Mine was first of all a block and beam concrete floor..yours will
probably be a slab, and this MUST finish at least 6" below finished
floor. and below damp course level. 8" is better..

THEN you blind that with a dry sand cement mixtuire to level it off and
get rid of any sharp edges and lay the insulation - slabs of whatever -
and the DPM - big plastic sheet - over it. Take the DPM up to over the
existing DPM level up the walls..you cut it off once its all finished -
and also run insulation up to finished floor level as well - this allows
a bit of expansion of the screed slab and prevents heat leaking into the
walls.

What you now have is a bowl shaped insulation layer. 50-75mm thick in
the middle, maybe 25mm up the edges. And at least 75mm deep..

Now you have a choice. yoiu CAN buty formers to lay teh plastic pipe
into, but I didn't bother. I shad to install metal reinforcing grid
anyway, so we simply tie wrapped the pipes to every other rod.

Pipe runs should never exceed 100 meters, and never ever be joined - use
a single length of pipe. If they have to pass thresholds slip a bit of
flexible conduit over to allow movement.

Pipes are ideally laid in a double spiral - think of it as a loop that
is coiled up -look at an old electric cooker element :-)

Once laid fit to your manifold and fill the pipes up and seal, and then
use a pressure gauge and pressure pump (I hired on for peanuts for a gew
days) to make sure no leaks are there, and *keep the pressure up at
around 5-6bar whilst laying screed*. Make sure that pipes are NOT run
where there is no need (under kitchen units: These simply will retain
the heat under the plinth, unless you punch holes in it) and where you
need to bolt or scew anything to the floor.

Then screed up to the finished floor level, cutting any excess DPM and
insulation with a stanley knife or serrated kitchen knife.

Add floor of your choice (UHH works REALLY well with stoine and tiles,
less well with laminate and vinyl, and is useless with carpet by and large)

The great advantage of UFH we have found is that in winter, its warm and
cosy, but in summer also, the slab stays cool..because we have mo
insulation between the room and the floor, it acts as a heat bank
stablizing temperatures during hot days to the daily mean.

wrote:
Christian McArdle wrote:
I have a solid concrete floor which we are ripping up and going to
re-lay.
You could try something like a Continental Solution 10 kit. Make sure,
whatever you choose, that the floor construction is appropriate before
laying any concrete.

http://www.discountedheating.co.uk/s...lution_10.html
http://www.continental-ufh.com

Christian.
If you really want to be warm, forget about underfloor heating.
Whenever I look at a these systems they invariably are used in
conjunction with other heaters and the owners just wont admit that they
are useless because they spent so much money putting them in.

Total ********


Its the sole form of heating here apart from open wires we only use on
the very coldest days, and they keep 250sq meters totally warm.

Done properly, its better than anything else.


Put a decent layer of insulation under the floor and leave it at that.

That is mandatory anyway.

Christian McArdle wrote:
If you really want to be warm, forget about underfloor heating.
Whenever I look at a these systems they invariably are used in
conjunction with other heaters and the owners just wont admit that they
are useless because they spent so much money putting them in.

Certainly, the numbers suggest that unless the room is well insulated, the
total heat output will be insufficient. However, they have significant
advantages over other methods. In particular, they are very useful in rooms
with tiled floors, such as bathrooms and kitchens, as they enable you to use
the room without having to find shoes or slippers. They are also useful in
wetter rooms, as puddles of water will evaporate more readily. Finally, the
heating will be much quieter than the alternative, which in most kitchens
would be a fan convector, as wall space is too valuable to use for passively
convected radiators.

That said, the fan convector has a considerable advantage in terms of
rapidity of heating. I think the best solution for a kitchen is to actually
have both underfloor and fan convector. This gives the best of both worlds,
with warm feet, rapid response and high total heat output.

In my own kitchen, I have a fan convector (plus an absolutely tiny radiator
that was there already that couldn't heat a cupboard, let alone a kitchen).
This does provide very effective and rapid heating. However, I do miss
having a warm floor and it is a pain in winter having to find footwear for
every foray into the room, unless the heating has been on for hours.

Christian.


Actually the best kitchen heater is an Aga.

You can cook on it too.

Christian McArdle wrote:
Not if your spouse suffers from serious cramp in her feet as a
consequence of arthritis. Why do you suggest that a kitchen requires
instantaneous heat? We spend more waking hours in our kitchen and
breakfast room than in any other part of the house.

There is an advantage in having rapidly responding heat output in a kitchen.
This is because the kitchen can hold other considerable heat producing
devices, such as ovens, microwaves, washing machines and hobs. A responsive
system can rapidly shut down, whilst a slow acting system may overheat the
room.


Not with a ruddy great slab of screed under it. That acts to stabilise
the temperatures.

Or 30 sq meter kitchen is totally heated except in the coldest of
conditions by an 700W output oil fired aga.

Cooking can kick out up to 2KW. Nothing can cope with losing that apart
from ventilation and fans or open windows.

In summer we shut the Aga down, and use the barbecue. Or an electric
stove ..The massive floor and its insulation keeps the kitchen cool.



This is why I think a composite system containing both fan convectors and a
low output underfloor system would work most effectively in a kitchen. It
is, however, I concede, not the cheapest option by a large marign.


Christian, your logic is wrong. Once the heat output on the room rises
above its heat loss, it doesn't matter how its heated. What matters is
how is cooled. UFH is ideal for places that are used a LOT. Its not so
ideal for - e.g/. a room used occasionally where you want fast heat up
and otherwise its left cool.

With the modern trend towards large kitchen/dining areas, UFH is
perfect. The kitchen is no longer the place you go into to prepare a
meal, it's where you live.



Christian.

mkkbb wrote:
Interesting thoughts brought up. I think the underfloor option will
probably be too expensive for me, but I will definately look into the
fan heaters. Thanks everyone.


If you are doing it from scratch is is very cheap.

I think that I spent around £300 on the pump/manifold and relay
stiff..beyond that teh cost of the pipe was no more than radiators, and
piping and the cost of laying it was a day on a computer drawing program
to plan the pipes, and about a morning laying it before the screeders
got busy. FAR less work than soldering up copper pipework is.

Given the cost of plumbers and the time it takes to lay copper, I think
it was actually cheaper.

Wiring it all up took me a day..probably he most challenging part
really. Got a Eurobox, DIN rails, stuck some large connector blocks in
and a relay, and a 3 zone timer, and spent a merry day connecting it all
together. There's a LOT of wire in there..

Richard wrote:
Christian McArdle wrote:



There is an advantage in having rapidly responding heat output in a
kitchen.
This is because the kitchen can hold other considerable heat producing
devices, such as ovens, microwaves, washing machines and hobs. A
responsive
system can rapidly shut down, whilst a slow acting system may overheat
the
room.

This is why I think a composite system containing both fan convectors
and a
low output underfloor system would work most effectively in a kitchen. It
is, however, I concede, not the cheapest option by a large marign.

Christian.



Hi Christian

Sorry, I intended to convey in my posting that I think a composite
system is sensible, but wanted to see why Dr D doesn't.

I don't think the very small advantages are worth the extra cost.
If the room is in use and heated the floor will come up to room temp
whether its heated or not. Kickspace only useful if you leave it cold,
and require rapid heating just when you are using it. I've got fan blown
heaters here, and they are great in the bedrooms - take up almost no
space, and heat them from icy to cosy in an hour or so..but they are
pretty useless if what you want is all day heat. Noisy and sometimes
smelly due to dust getting trapped in them.

Dr Drivel can safely be ignored on all issues - I think that the rest of
us who may disagree on other things, would agree on that point.



Richard

David Hansen wrote:
On 14 Aug 2006 03:25:41 -0700 someone who may be "mkkbb"
wrote this:-

I have a solid concrete floor which we are ripping up and going to
re-lay.

In addition to operating the underfloor heating at a lower
temperature to radiators, so that people can stand on the floor,

So that the floor is not destroyed...

underfloor heating also has different time characteristics. It can
be turned off earlier than radiators (because the floor provides
thermal storage) and will probably need to be turned on earlier.
Thus it should be on a separate time control, have a room thermostat
and ideally the pump and mixing valve should be arranged to
compensate for outside temperature. All this is no great hardship as
controllers are available to do all of this.

Yes to all of that.

I run about a three hour lead on hours..strangely enough it only takes
about half an hour from switchoff before you notice that its off..the
heating is SO constant and even that the slightest change - a door
opening etc - makes you realise its changed. In deepest winter I run it
24x7 anyway, because we have so much thermal mass it scarcely makes any
difference to the cost.

We find that we don't have any hot or cold spots though - apart from
under the sofa. THAT is up to maybe 35C sometimes..the pets LOVE UFH.

The message
from The Natural Philosopher contains these words:

You MUST insulate the floor though, or it will be bearer 400W/sq meter,
with you providing a nice little soil heater for the worms..

Not to mention being illegal. Though some of the recent rules are rather
daft, the one insisting on proper insulation under solid floors makes
sense. I've got 4" under the conservatory floor.

--
Skipweasel
Pay no attention to that man behind the curtain.

The message
from The Natural Philosopher contains these words:

Pipes are ideally laid in a double spiral

That's important, that bit. Without it you'll end up with one end of the
floor getting a lot hotter than the other.

The spiral in then spiral back out again in between the incoming spiral
system means that the slab warms up evenly.

--
Skipweasel
Pay no attention to that man behind the curtain.

This is why I think a composite system containing both fan convectors and
a
low output underfloor system would work most effectively in a kitchen. It
is, however, I concede, not the cheapest option by a large marign.

Christian, your logic is wrong. Once the heat output on the room rises
above its heat loss, it doesn't matter how its heated.

Not quite. Take an example:

The heat loss is 1kW and the UFH is kicking out a 1kW, which is quite
reasonable. A nice stable temperature.

Now start cooking at about 1.5kW. You are now shoving in 2.5kW which will
rapidly heat the room by 1.5kW excess. Even if the stat kicks in
immediately, the UFH will give 1kW for some time.

If you had a fan convector, it would shut down immediately, giving 1.5kW,
which gives only 500W too much, which could be easily dissipated by opening
an internal door and using the heat in other rooms.

If you had a composite system, you'd probably set the floor temperature to
25C, which is comfortable to the feet, but would not add significantly to
the heating of a room already to temperature, perhaps a few hundred watts at
most.

Christian.

The message
from "Christian McArdle" contains
these words:

Now start cooking at about 1.5kW. You are now shoving in 2.5kW which will
rapidly heat the room by 1.5kW excess.

That assumes the 1.5kW is constant. In the case of a modern oven it'll
only be for a few minutes at the outset, and again every now and again
to keep it hot. In the case of boiling something, again you'd be using
that much perhap to raise something to the boil but with a lid on you
don't need anything like that much to keep it boiling. If the extractor
fan's running and removing steam that's much of your energy gone
straight away as water vapour carries a lot of heat.

--
Skipweasel
Pay no attention to that man behind the curtain.

Now start cooking at about 1.5kW. You are now shoving in 2.5kW which will
rapidly heat the room by 1.5kW excess.

That assumes the 1.5kW is constant. In the case of a modern oven it'll
only be for a few minutes at the outset, and again every now and again
to keep it hot.

1.5kW is a nice average for cooking a meal, rather than reheating something
in the oven. The peak output could be as high as 10kW for Christmas dinner.

Christian.

The Natural Philosopher wrote:
Christian.
If you really want to be warm, forget about underfloor heating.
Whenever I look at a these systems they invariably are used in
conjunction with other heaters and the owners just wont admit that they
are useless because they spent so much money putting them in.

Total ********


Its the sole form of heating here apart from open wires we only use on
the very coldest days, and they keep 250sq meters totally warm.

Done properly, its better than anything else.


Put a decent layer of insulation under the floor and leave it at that.

That is mandatory anyway.


Seems to me that you are dishing out advice to people and you really
dont even know what you are talking about.
In another thread you were offering your inside wisdom on wood burning
stoves and you dont even have one.
Then you said you had a large open fire and now you claim to have under
floor heating.
And you then rubbish other people's advices.
I really think you should change that misleading name you put on
yourself.
If the UFH is so great why do you need a large open fire?
If the open fire is so great why do you need the UFH?
Your advice is seriously misleading to genuine enquirers so please
restrain your advice to matters that you actually know about.

If the UFH is so great why do you need a large open fire?
If the open fire is so great why do you need the UFH?

They do different things. UFH is great at heating a house very comfortably
and efficiently.

An open fire is great to look at. Pathetic at providing low maintenance, low
cost comfortable day to day heat, but really nice now and again.

Christian.

On Tue, 15 Aug 2006 11:05:33 +0100, Christian McArdle wrote:

An open fire is great to look at. Pathetic at providing low maintenance, low
cost comfortable day to day heat, but really nice now and again.

Hmm, I find an open fire with a properly designed back boiler to be an
excellent source of cheap comfortable heat. If the back boiler is feeding a
heat bank, it's also a good way to provide UFH as well.