hello again,
my flat is ground floor and has concrete floors throughout. it
currently has central heating run from a year-old combination boiler.
the central heating, i think, was installed some years after the
property was built, as there are twin pipes running along the bottom
of various walls, linking the radiators.
i am planning to replace all the floors in time, and was wondering
whether underfloor heating is an option? my kitchen has just been re
plastered and has no radiator, so i was going to start in there, using
it under ceramic tiles.
has anybody any experience of underfloor heating? is it the future?
should i use a water system and run it from the combi boiler? or go
electric (and use the combi solely for hot water).
i'd like to end up with an energy efficient home, and am prepared to
spend if it will be worthwhile. it would also mean i can get rid of
all the radiators and ugly pipes running along the walls!
thanks

The message

from benpost contains these words:

hello again,
my flat is ground floor and has concrete floors throughout. it
currently has central heating run from a year-old combination boiler.
the central heating, i think, was installed some years after the
property was built, as there are twin pipes running along the bottom
of various walls, linking the radiators.
i am planning to replace all the floors in time, and was wondering
whether underfloor heating is an option? my kitchen has just been re
plastered and has no radiator, so i was going to start in there, using
it under ceramic tiles.
has anybody any experience of underfloor heating? is it the future?
should i use a water system and run it from the combi boiler? or go
electric (and use the combi solely for hot water).
i'd like to end up with an energy efficient home, and am prepared to
spend if it will be worthwhile. it would also mean i can get rid of
all the radiators and ugly pipes running along the walls!
thanks

I am currently considering much the same except that I intend to leave
the kitchen as it is (it is at a lower level) and only dig up the floor
in the main part of the house. If you have gas then I would have thought
that gas has much the cheaper operating costs.

Wet underfloor heating operates at a lower temperature than conventional
radiators (max 45C IIRC) so it needs to be a separate circuit with a
separate control system to any remaining radiators (which might not be a
problem in your flat). It also has a much slower response time which
means it is better suited to those who are at home more often than not.

But be aware that digging up a concrete floor, particularly a modern
one, is a major undertaking and one that would in all probability
require some additional excavation to cope with the extra thickness of
the floor resulting from the insulation layer and the pipe layer. Even
if you have some insulation under the floor it is unlikely to be
sufficient for an underfloor heating system.

I don't know whether your property being a flat (and presumably being
leasehold) effects the case but you would be wise to explore that issue
before you start ripping up your floor.

--
Roger Chapman

benpost wrote:
hello again,
my flat is ground floor and has concrete floors throughout. it
currently has central heating run from a year-old combination boiler.
the central heating, i think, was installed some years after the
property was built, as there are twin pipes running along the bottom
of various walls, linking the radiators.
i am planning to replace all the floors in time, and was wondering
whether underfloor heating is an option? my kitchen has just been re
plastered and has no radiator, so i was going to start in there, using
it under ceramic tiles.
has anybody any experience of underfloor heating? is it the future?
should i use a water system and run it from the combi boiler? or go
electric (and use the combi solely for hot water).
i'd like to end up with an energy efficient home, and am prepared to
spend if it will be worthwhile. it would also mean i can get rid of
all the radiators and ugly pipes running along the walls!
thanks

Currently its very inefficiennt unless used with a lot of underfloor
insulation. So yiu have to dig out the whole floor and replace.

Currently water baseed systems are cheaperto run than electric.

Unless you are prepared to do it properly, don't do it at all. You will
be disappointed.

i am property thinking bigger than is realisticly possible...

back to the kitchen, which currently has no radiator, and needs a new
floor (once i remove the 70% covering of ceramic tiles). could i try
installing the electrical underfloor heating before laying new ceramic
tiles?

perhaps that would be an easier introduction to underfloor heating...

benpost wrote:
i am property thinking bigger than is realisticly possible...

back to the kitchen, which currently has no radiator, and needs a new
floor (once i remove the 70% covering of ceramic tiles). could i try
installing the electrical underfloor heating before laying new ceramic
tiles?

perhaps that would be an easier introduction to underfloor heating...

Unless you insulate under, you will be bleeding about 85% of the heat to
warm the planet, not your kitchen.

And the electric costs are about 3 times what oil gas would cost.

If you just want a warm kitchen put in fan blown under unit heaters
'kickspace' and connect them to your wet system.

Add a nice spongy vinyl floor and it will be very nice for your feet.

Use a kitchen stat to control the fans otherwise it will rapidly
overheat when cooking.

Fan blown wet heaters are pretty damn efficient at bringing a room up to
temperature quickly.

In article
,
benpost wrote:
i am property thinking bigger than is realisticly possible...

back to the kitchen, which currently has no radiator, and needs a new
floor (once i remove the 70% covering of ceramic tiles). could i try
installing the electrical underfloor heating before laying new ceramic
tiles?

perhaps that would be an easier introduction to underfloor heating...

The big snag with underfloor heating is that it is extremely slow to react
to ambient temperature. So not a brilliant idea with the UK climate. Can
be very useful for background heating if the energy used is cheap - like
say from a heat pump source. But will be extremely costly to run using
full price electricity.

--
*You! Off my planet!

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article
,
benpost wrote:
i am property thinking bigger than is realisticly possible...

back to the kitchen, which currently has no radiator, and needs a new
floor (once i remove the 70% covering of ceramic tiles). could i try
installing the electrical underfloor heating before laying new ceramic
tiles?

perhaps that would be an easier introduction to underfloor heating...

The big snag with underfloor heating is that it is extremely slow to react
to ambient temperature. So not a brilliant idea with the UK climate. Can
be very useful for background heating if the energy used is cheap - like
say from a heat pump source. But will be extremely costly to run using
full price electricity.

The great thing about underfloor heating is that it doesn't HAVE to
react to ambient temperatures,. It CONTROLS them by dint of a large slab
of concrete floor.

I can some some issues in a kichen, which may get hot and steamy
quickly, and need fans to remove this, but thats what happens in
kitchens. They tend - when used purely to cook - to be kept cool, and
ventilated when being used.

I have never quite understood this trend towards 'kitchen diners'

The last thing I want to do is sit down to eat and gaze at a pile of
dirty saucepans and plates etc..kitchens are industrial areas.

On 10 Jan, 14:25, The Natural Philosopher wrote:
benpost wrote:
i am property thinking bigger than is realisticly possible...

back to the kitchen, which currently has no radiator, and needs a new
floor (once i remove the 70% covering of ceramic tiles). could i try
installing the electrical underfloor heating before laying new ceramic
tiles?

perhaps that would be an easier introduction to underfloor heating...

Unless you insulate under, you will be bleeding about 85% of the heat to
warm the planet, not your kitchen.

And the electric costs are about 3 times what oil gas would cost.

If you just want a warm kitchen put in fan blown under unit heaters
'kickspace' and connect them to your wet system.

Add a nice spongy vinyl floor and it will be very nice for your feet.

Use a kitchen stat to control the fans otherwise it will rapidly
overheat when cooking.

Fan blown wet heaters are pretty damn efficient at bringing a room up to
temperature quickly.

As usual, I second what the NP has said in this post and agree with
the chap who said
either do the lot or not

Lot of effort to dig up old concrete and oversite and lay at least 4"
of insulation needed ... complete waste of money unless rest of house
up to scratch as only about 10% is lost thru floors
best spend the money elsewere on insulation
chris

In article ,
The Natural Philosopher wrote:
The big snag with underfloor heating is that it is extremely slow to
react to ambient temperature. So not a brilliant idea with the UK
climate. Can be very useful for background heating if the energy used
is cheap - like say from a heat pump source. But will be extremely
costly to run using full price electricity.

The great thing about underfloor heating is that it doesn't HAVE to
react to ambient temperatures,. It CONTROLS them by dint of a large slab
of concrete floor.

And when the sun streams in through windows?

I can some some issues in a kichen, which may get hot and steamy
quickly, and need fans to remove this, but thats what happens in
kitchens. They tend - when used purely to cook - to be kept cool, and
ventilated when being used.

Hence the need for a system that reacts quickly to avoid wasting energy
while making the room comfortable at the start of the day.

I have never quite understood this trend towards 'kitchen diners'

The last thing I want to do is sit down to eat and gaze at a pile of
dirty saucepans and plates etc.

No dishwasher to hide them in?

.kitchens are industrial areas.

Some consider cooking more of a pleasure than just work.

--
*How many roads must a man travel down before he admits he is lost?

Dave Plowman London SW
To e-mail, change noise into sound.

On 10 Jan, 10:43, benpost wrote:
hello again,
my flat is ground floor and has concrete floors throughout. it
currently has central heating run from a year-old combination boiler.
the central heating, i think, was installed some years after the
property was built, as there are twin pipes running along the bottom
of various walls, linking the radiators.
i am planning to replace all the floors in time, and was wondering
whether underfloor heating is an option? *my kitchen has just been re
plastered and has no radiator, so i was going to start in there, using
it under ceramic tiles.
has anybody any experience of underfloor heating? is it the future?
should i use a water system and run it from the combi boiler? or go
electric (and use the combi solely for hot water).
i'd like to end up with an energy efficient home, and am prepared to
spend if it will be worthwhile. it would also mean i can get rid of
all the radiators and ugly pipes running along the walls!
thanks

AFAIK the wet systems are more efficient but then you have concern of
if there are any leaks.
The pure electric systems don't have that concern but are more
expensive to run

One advantage is it tidies the rooms up as no radiators & pipes...
good for new 'minimalist' flats. But I am not sure if it is 'central'
heating or metered to individual flats. There is the issue of who is
responsible for 'common' parts of a block of flats (which should be
spelt out in the lease).

I definitely wouldn't change from what you currently have, it just
sounds like a lot of aggravation.

On 10 Jan, 14:54, The Natural Philosopher wrote:
Dave Plowman (News) wrote:
In article
,
benpost wrote:
i am property thinking bigger than is realisticly possible...

back to the kitchen, which currently has no radiator, and needs a new
floor (once i remove the 70% covering of ceramic tiles). could i try
installing the electrical underfloor heating before laying new ceramic
tiles?

perhaps that would be an easier introduction to underfloor heating...

The big snag with underfloor heating is that it is extremely slow to react
to ambient temperature. So not a brilliant idea with the UK climate. Can
be very useful for background heating if the energy used is cheap - like
say from a heat pump source. But will be extremely costly to run using
full price electricity.

The great thing about underfloor heating is that it doesn't HAVE to
react to ambient temperatures,. It CONTROLS them by dint of a large slab
of concrete floor.

I can some some issues in a kichen, which may get hot and steamy
quickly, and need fans to remove this, but thats what happens in
kitchens. They tend - when used purely to cook - to be kept cool, and
ventilated when being used.

I have never quite understood this trend towards 'kitchen diners'

The last thing I want to do is sit down to eat and gaze at a pile of
dirty saucepans and plates etc..kitchens are industrial areas.

I think what is interesting is how often we have actually to drive our
guests through from our diner/kitchen (living room) away through to
the lounge. Unless you, and I mean you NP, have a particularly lounge
area which has so much space that people feel comfortable in it, there
is a whole lot of us who have a general living space that is in the
end the most comfortable area in the house and that's where our guests
tend to congregate. Can't remember now quite what the song said about
parties in the kitchen, but it was totally accurate.

Rob

Dave Plowman (News) wrote:
In article ,
The Natural Philosopher wrote:
The big snag with underfloor heating is that it is extremely slow to
react to ambient temperature. So not a brilliant idea with the UK
climate. Can be very useful for background heating if the energy used
is cheap - like say from a heat pump source. But will be extremely
costly to run using full price electricity.

The great thing about underfloor heating is that it doesn't HAVE to
react to ambient temperatures,. It CONTROLS them by dint of a large slab
of concrete floor.

And when the sun streams in through windows?

Blinds. In pur houyse, in winter, teh sun strems in, and that mens the
UFH comes on less. Thats all,. In summer it doesn;lt come on at all, and
w draw the curtians by day.

In spring and autimn, instead of cycling between about 15 and 20C sing
the UFH on a timer, the UFH simply doesn't come on unless there is a
really cold night followed by a dull day.

The massive concrete floors reduce diurnal fluctuatains to 3-5 degrees
at the most,and slow down temp rises to at most about 1C per hour from
solar - well within a UFH response time.



I can some some issues in a kichen, which may get hot and steamy
quickly, and need fans to remove this, but thats what happens in
kitchens. They tend - when used purely to cook - to be kept cool, and
ventilated when being used.

Hence the need for a system that reacts quickly to avoid wasting energy
while making the room comfortable at the start of the day.

I have never quite understood this trend towards 'kitchen diners'

The last thing I want to do is sit down to eat and gaze at a pile of
dirty saucepans and plates etc.

No dishwasher to hide them in?


Well you still have to take them out to wash them. No dishwasher yet can
cope with carbonised stew at the bottom of the pan, or porridge, or a
roasting tin..or..about 30 other dishes that leave a sticky residue.
Scrambled eggs is another one. They don't even get dried coffee out of
the cups.


I guess if you microwave pizzas and pot noodles, its fine..



.kitchens are industrial areas.

Some consider cooking more of a pleasure than just work.

Some consider working at a lathe or milling machine pleasure. I do
personally. Doesn't mean I want to eat my luncch off an angle grinder,
or look at a swarf covered floor while I do it.

wrote:
On 10 Jan, 10:43, benpost wrote:
hello again,
my flat is ground floor and has concrete floors throughout. it
currently has central heating run from a year-old combination boiler.
the central heating, i think, was installed some years after the
property was built, as there are twin pipes running along the bottom
of various walls, linking the radiators.
i am planning to replace all the floors in time, and was wondering
whether underfloor heating is an option? �my kitchen has just been re
plastered and has no radiator, so i was going to start in there, using
it under ceramic tiles.
has anybody any experience of underfloor heating? is it the future?
should i use a water system and run it from the combi boiler? or go
electric (and use the combi solely for hot water).
i'd like to end up with an energy efficient home, and am prepared to
spend if it will be worthwhile. it would also mean i can get rid of
all the radiators and ugly pipes running along the walls!
thanks

AFAIK the wet systems are more efficient but then you have concern of
if there are any leaks.

With continuous runs of plastic pipe, there are no leaks.

The pure electric systems don't have that concern but are more
expensive to run

One advantage is it tidies the rooms up as no radiators & pipes...
good for new 'minimalist' flats. But I am not sure if it is 'central'
heating or metered to individual flats. There is the issue of who is
responsible for 'common' parts of a block of flats (which should be
spelt out in the lease).

I definitely wouldn't change from what you currently have, it just
sounds like a lot of aggravation.

I would IF you have the balls to do the job properly.

Otherwise the kickspace units are high output per unit area, and use
dead space under the units, and produce warm air at tootsie level.
Excellent.

robgraham wrote:
On 10 Jan, 14:54, The Natural Philosopher wrote:
Dave Plowman (News) wrote:
In article
,
benpost wrote:
i am property thinking bigger than is realisticly possible...
back to the kitchen, which currently has no radiator, and needs a new
floor (once i remove the 70% covering of ceramic tiles). could i try
installing the electrical underfloor heating before laying new ceramic
tiles?
perhaps that would be an easier introduction to underfloor heating...
The big snag with underfloor heating is that it is extremely slow to react
to ambient temperature. So not a brilliant idea with the UK climate. Can
be very useful for background heating if the energy used is cheap - like
say from a heat pump source. But will be extremely costly to run using
full price electricity.
The great thing about underfloor heating is that it doesn't HAVE to
react to ambient temperatures,. It CONTROLS them by dint of a large slab
of concrete floor.

I can some some issues in a kichen, which may get hot and steamy
quickly, and need fans to remove this, but thats what happens in
kitchens. They tend - when used purely to cook - to be kept cool, and
ventilated when being used.

I have never quite understood this trend towards 'kitchen diners'

The last thing I want to do is sit down to eat and gaze at a pile of
dirty saucepans and plates etc..kitchens are industrial areas.

I think what is interesting is how often we have actually to drive our
guests through from our diner/kitchen (living room) away through to
the lounge. Unless you, and I mean you NP, have a particularly lounge
area which has so much space that people feel comfortable in it, there
is a whole lot of us who have a general living space that is in the
end the most comfortable area in the house and that's where our guests
tend to congregate. Can't remember now quite what the song said about
parties in the kitchen, but it was totally accurate.


Well we have three 30 sq meter spaces..kitchen plus eating, full blown
dining room and the 'horizontal' area with the telly.

The dining room gets the lest use, but did sterling service over
Xmas,when we actually had three cookers on the go..in two kitchens..ask
not why the place is organised this way..history..

We eat in the kitchen mainly, because its quick. Or on trays in front of
the TV,. cos we are slobs. I keep intending to part partition te kitchen
to increase the separation a bit more.


Rob

In article ,
AJH wrote:
On Thu, 10 Jan 2008 17:06:09 +0000 (GMT), "Dave Plowman (News)"
wrote:
NP wrote
The great thing about underfloor heating is that it doesn't HAVE to
react to ambient temperatures,. It CONTROLS them by dint of a large
slab of concrete floor.

And when the sun streams in through windows?

One of the theories behind having low temperature circulating water
in the slab was that if the slab was at 25C and the air temperature in
the room rose then as the temperature difference decreased less heat
left the slab. Given a large slab area for heat exchange this should
be largely self regulating, in theory. In practice I see a number of
problems with one multi occupancy building with underfloof heating and
a limited heat input.

Like all thermal mass systems it also depends on having a fairly constant
energy input to it. So ok if only providing background heating to say 55F.
If required to provide the more usual 70F or so it simply won't react
quickly enough to a change in room temperature for whatever reason.

Nothing new about underfloor heating. It's been round long enough for the
disadvantages to be known. As has the conventional water
circulation/radiator type - which is why it dominates the market.

AJH

--
*Stable Relationships Are For Horses. *

Dave Plowman London SW
To e-mail, change noise into sound.

On Fri, 11 Jan 2008 13:14:01 +0000, Dave Plowman (News) wrote:

And when the sun streams in through windows?

One of the theories behind having low temperature circulating water
in the slab was that if the slab was at 25C and the air temperature in
the room rose then as the temperature difference decreased less heat
left the slab. Given a large slab area for heat exchange this should
be largely self regulating, in theory. In practice I see a number of
problems with one multi occupancy building with underfloof heating and
a limited heat input.

Like all thermal mass systems it also depends on having a fairly constant
energy input to it.

I don't see this. I'm not intending to defend underfloor heating as I
don't have much experience of it, that I do have is from brief visits to a
system that appears to be marginal in longer periods of cold weather,
exacerbated by unexpected heat bleeds as the thermal store is depleted.
The heat inputs to this can be both unscheduled or on demand for the wood
fired back up system (which runs 24/7 except for a forced reboot every 4
hours in weather like now).


So ok if only providing background heating to say 55F.
If required to provide the more usual 70F or so it simply won't react
quickly enough to a change in room temperature for whatever reason.

I'm not saying you are wrong but you missed the point of my post, which
was the power emitted by the slab is subject to negative feedback from the
air above.

So if the slab emits 10kW(t) into the room when the slab is at 25C and
the room is at 10C it should emit no power when the room is at 25C.
Having said that I do know from looking at the circulating temperature
in the underfloor pipes that the water circuit return is still ~39C when
I was expecting to see only a bit above 25C.

AJH

On Thu, 10 Jan 2008 14:25:36 +0000, The Natural Philosopher wrote:

Fan blown wet heaters are pretty damn efficient at bringing a room up to
temperature quickly

I advocated these in series with the underfloor heating ( or rather having
their return into the underfloor heating circuit injector) to get the air
temperatures up whilst still returning low temperature water to the
thermal store. to give people a quick warmth after being out for the day
without having to anticipate how the underfloor system would be working
when they got home.

In practice people were leaving the room stat too high and then finding it
hot when they got in, which could only be mitigated by opening windows.

AJH

The message . uk
from andrew heggie contains these words:

In practice people were leaving the room stat too high and then finding it
hot when they got in, which could only be mitigated by opening windows.

Was this due to the widespread belief that turning the room stat up
increases the heating rate or lack of a predictive controller which I
would have thought was essential with a large time constant in the
equation.

--
Roger Chapman

On Fri, 11 Jan 2008 20:46:57 +0000, Roger wrote:

In practice people were leaving the room stat too high and then finding it
hot when they got in, which could only be mitigated by opening windows.

Was this due to the widespread belief that turning the room stat up
increases the heating rate or lack of a predictive controller which I
would have thought was essential with a large time constant in the
equation.

That may have been a part of it but I'm thinking it's a foible of the
ethos of the designers and owners, it's sort of social housing for key
workers. There is no provision for monitoring any tenant's heat use and I
have no way of knowing if the software has any predictive element to it.
In the event it would make no difference because without sunshine there's
no way the backup can meet the power demanded of it by the tenants. As I
said this leads to this, and another, heat bleed that just makes things
worse.

They are so tight that they wouldn't even allow for a link to the
internet and a webserver (which could have been by arrangement with a
tenant's broadband) so I could monitor what was happening, I am two hours
away and some failures are very easy to deal with but I don't get called
until the thermal store is depleted.

AJH

Dave Plowman (News) wrote:
In article ,
AJH wrote:
On Thu, 10 Jan 2008 17:06:09 +0000 (GMT), "Dave Plowman (News)"
wrote:
NP wrote
The great thing about underfloor heating is that it doesn't HAVE to
react to ambient temperatures,. It CONTROLS them by dint of a large
slab of concrete floor.
And when the sun streams in through windows?

One of the theories behind having low temperature circulating water
in the slab was that if the slab was at 25C and the air temperature in
the room rose then as the temperature difference decreased less heat
left the slab. Given a large slab area for heat exchange this should
be largely self regulating, in theory. In practice I see a number of
problems with one multi occupancy building with underfloof heating and
a limited heat input.

Like all thermal mass systems it also depends on having a fairly constant
energy input to it.
?
what?

Are?
You talking about?

So ok if only providing background heating to say 55F.

Total utter ********!
If required to provide the more usual 70F or so it simply won't react
quickly enough to a change in room temperature for whatever reason.

You haven';t a clue, have you?

Nothing new about underfloor heating. It's been round long enough for the
disadvantages to be known. As has the conventional water
circulation/radiator type - which is why it dominates the market.


It dominates teh market because we didn;t have propelt isnualted house,
and its gfar esier to istall after market.

UFH is FAR better and more comfortable and FAR more even in
temperature..if its done as part of the overall design.

Mine is perfectly capable of heating the rooms its in to well in excess
of 25C. And that's the temperature they STAY at. Because there's about 4
tons of floor in each one a..open a window, cold air flows in..shut it,
and within minutes that 4 tons of concrete has warmed it back up, using
nice natural convection.

The whole point about an in-screed UFH is that it is almost IMPOSSIBLE
to change the room temperature quickly. We have the UFH on, and then
light fires as well. Our open fire kicks out about 5Kw plus. It STILL
takes about an hour to pull the room up one and a half degrees. Theres
about 1500W of UFH in there. That takes even longer. But conversely, if
you shut it down at midnight, its only dripped three degrees by morning,
on the coldest nights.

Rooms which do NOT have the thermal mass like upstair rooms with wooden
floors, warm up just as quickly with UFH as with anything else, and cool
down as fast.
UFH is after all just a radaiotor spread flat across the floor.

The biggest advantage we find is this. In order to not feel cold, it
seems that you want the coldest part of your body to be at a given
temperature. With UFH there is no cold layer of air arund your feet. So
we actually feel warmer at lower temperures. ~The whole room is utterly
even in temperature. Ther are no hot spots near radiators, no problems
with them being blanked off by curatins or sofa..any cold air off
windows slips to the floor and get warmed befoire it rises to warm the
rest of the room. The walls being the coldest parts with the windows,
set up mild downward flows, so you get an overall convection in the
middle of the room, which is warmest, and cold edges.

With radiators the edges are warm, and the cooler downdraiught is in the
center, where you are sitting.

Net result, you run the room hotter at the edges- where the losses are -
to compensate. And hotter overall, to keep your feet warm.
Radiators are a triumph of convenience over results. UFH is way ahead in
the comfort and economy stakes, but its a total bitch to retrofit
PROPERLY, which is why its got a bad name.












AJH

andrew heggie wrote:
On Fri, 11 Jan 2008 13:14:01 +0000, Dave Plowman (News) wrote:

And when the sun streams in through windows?
One of the theories behind having low temperature circulating water
in the slab was that if the slab was at 25C and the air temperature in
the room rose then as the temperature difference decreased less heat
left the slab. Given a large slab area for heat exchange this should
be largely self regulating, in theory. In practice I see a number of
problems with one multi occupancy building with underfloof heating and
a limited heat input.
Like all thermal mass systems it also depends on having a fairly constant
energy input to it.

I don't see this. I'm not intending to defend underfloor heating as I
don't have much experience of it, that I do have is from brief visits to a
system that appears to be marginal in longer periods of cold weather,
exacerbated by unexpected heat bleeds as the thermal store is depleted.
The heat inputs to this can be both unscheduled or on demand for the wood
fired back up system (which runs 24/7 except for a forced reboot every 4
hours in weather like now).


So ok if only providing background heating to say 55F.
If required to provide the more usual 70F or so it simply won't react
quickly enough to a change in room temperature for whatever reason.

I'm not saying you are wrong but you missed the point of my post, which
was the power emitted by the slab is subject to negative feedback from the
air above.

So if the slab emits 10kW(t) into the room when the slab is at 25C and
the room is at 10C it should emit no power when the room is at 25C.
Having said that I do know from looking at the circulating temperature
in the underfloor pipes that the water circuit return is still ~39C when
I was expecting to see only a bit above 25C.

Yes. Plastic pipes do not conduct that well. I can put my hands on the
flow pipes at and alleged 60C and they do not burn. So thats one barrier
the heat has to overcome.

The most interesting thing I have found is that under the sofa, the
floor temps are as high as an estimated 30C. We have 4" of screed, a
layer of plastic underlay foam and wood laminate as well..that isn'y
hugley conductive either. So the screed center is fairly warm I giuess,
but it is cool on the outside..due really to that being teh most
conductive part. Airflow really works to cool it.

Rhe thermal; mass issue ois merely one of time. It acts to stabilise
temperature massively. The summer before last - the hot one - we stayed
inside with the windows CLOSED and the curtains drawn, and stayed below
25C while the air outside was in the mid /high 30's.

Airflow was minimal and via the fire underfloor vents, and chimney and
the underfloor space was shady and cool as well..

In another house where there is some unintentional UFH due to copper
pipes unlagged running under a bathroom floor, they rate of temperature
increase is totally different.Its warm within minutes..and cools just as
fast.

If you want rapid heat rises, just use a suspended floor and lay the
pipes in air over insulation. Its about the same as a conventional rad,
except the more diffuse heat source is far more pleasant.














AJH

andrew heggie wrote:
On Thu, 10 Jan 2008 14:25:36 +0000, The Natural Philosopher wrote:

Fan blown wet heaters are pretty damn efficient at bringing a room up to
temperature quickly

I advocated these in series with the underfloor heating ( or rather having
their return into the underfloor heating circuit injector) to get the air
temperatures up whilst still returning low temperature water to the
thermal store. to give people a quick warmth after being out for the day
without having to anticipate how the underfloor system would be working
when they got home.

In practice people were leaving the room stat too high and then finding it
hot when they got in, which could only be mitigated by opening windows.


Its impossible to legislate for stupidity. The same will happen in any
high thermal mass house that is subject to overheating.

We KNOW what temperature we like to sit in - 19C-21C depending on the RH.

Its imply a matter of setting the stat. No point in timers..not with te
thermal mass we have...with ANY form of heating.



AJH

In article ,
The Natural Philosopher wrote:
Dave Plowman (News) wrote:
In article ,
AJH wrote:
On Thu, 10 Jan 2008 17:06:09 +0000 (GMT), "Dave Plowman (News)"
wrote:
NP wrote
The great thing about underfloor heating is that it doesn't HAVE to
react to ambient temperatures,. It CONTROLS them by dint of a large
slab of concrete floor.
And when the sun streams in through windows?

One of the theories behind having low temperature circulating water
in the slab was that if the slab was at 25C and the air temperature in
the room rose then as the temperature difference decreased less heat
left the slab. Given a large slab area for heat exchange this should
be largely self regulating, in theory. In practice I see a number of
problems with one multi occupancy building with underfloof heating and
a limited heat input.

Like all thermal mass systems it also depends on having a fairly constant
energy input to it.
?
what?

Are?
You talking about?

I'm saying it is slow to react to any changes in input energy or heat
output.

So ok if only providing background heating to say 55F.

Total utter ********!
If required to provide the more usual 70F or so it simply won't react
quickly enough to a change in room temperature for whatever reason.

You haven';t a clue, have you?

Nothing new about underfloor heating. It's been round long enough for
the disadvantages to be known. As has the conventional water
circulation/radiator type - which is why it dominates the market.


It dominates teh market because we didn;t have propelt isnualted house,
and its gfar esier to istall after market.

It's still not common on new builds either.

UFH is FAR better and more comfortable and FAR more even in
temperature..if its done as part of the overall design.

I don't want an even temperature throughout the day. That would be a
disadvantage - apart from any running cost issues.

Mine is perfectly capable of heating the rooms its in to well in excess
of 25C. And that's the temperature they STAY at. Because there's about 4
tons of floor in each one a..open a window, cold air flows in..shut it,
and within minutes that 4 tons of concrete has warmed it back up, using
nice natural convection.

Very energy efficient. Not.

The whole point about an in-screed UFH is that it is almost IMPOSSIBLE
to change the room temperature quickly. We have the UFH on, and then
light fires as well. Our open fire kicks out about 5Kw plus. It STILL
takes about an hour to pull the room up one and a half degrees. Theres
about 1500W of UFH in there. That takes even longer. But conversely, if
you shut it down at midnight, its only dripped three degrees by morning,
on the coldest nights.

Which means it's using the energy input inefficiently.

Rooms which do NOT have the thermal mass like upstair rooms with wooden
floors, warm up just as quickly with UFH as with anything else, and cool
down as fast.
UFH is after all just a radaiotor spread flat across the floor.

Err, either the idea of a large thermal mass is a good one or not. So
which is it? You apparently seem to have both.

And I'd take issue that an underfloor system with wood floors can react as
quickly as conventional rads can. For a start there will be a much greater
mass of water in the heating coils than in equivalent rads. It then has to
find its way through the floor and covering - both of which will be decent
insulators.

The biggest advantage we find is this. In order to not feel cold, it
seems that you want the coldest part of your body to be at a given
temperature. With UFH there is no cold layer of air arund your feet. So
we actually feel warmer at lower temperures. ~The whole room is utterly
even in temperature. Ther are no hot spots near radiators, no problems
with them being blanked off by curatins or sofa..any cold air off
windows slips to the floor and get warmed befoire it rises to warm the
rest of the room. The walls being the coldest parts with the windows,
set up mild downward flows, so you get an overall convection in the
middle of the room, which is warmest, and cold edges.

So you've moved the draughts round a bit?

With radiators the edges are warm, and the cooler downdraiught is in the
center, where you are sitting.

Net result, you run the room hotter at the edges- where the losses are -
to compensate. And hotter overall, to keep your feet warm.
Radiators are a triumph of convenience over results. UFH is way ahead in
the comfort and economy stakes, but its a total bitch to retrofit
PROPERLY, which is why its got a bad name.

It's pointless in a house with suspended wood floors.












AJH


--
*If a pig loses its voice, is it disgruntled?

Dave Plowman London SW
To e-mail, change noise into sound.

The message
from "Dave Plowman (News)" contains these words:

With radiators the edges are warm, and the cooler downdraiught is in the
center, where you are sitting.

Net result, you run the room hotter at the edges- where the losses are -
to compensate. And hotter overall, to keep your feet warm.
Radiators are a triumph of convenience over results. UFH is way ahead in
the comfort and economy stakes, but its a total bitch to retrofit
PROPERLY, which is why its got a bad name.

It's pointless in a house with suspended wood floors.

My nearest neighbour has just had a bungalow built in his garden. He
opted for underfloor heating with a suspended wooden floor. He wouldn't
agree with you.

--
Roger Chapman