Hi all,

I am looking to fit underfloor heating in a room of around 40m2 in a
new extension. The floor slab is down and have plenty of room for
insulation, heating etc before we get to the finished floor level.
Looking at the polyplumb website, they seem to do 2 main types which
could be used on the ground floor on top of the slab...
1. the traditional solid floor type - ie the pipes are laid in the
screed
2. a "floating floor" type - where you lay some boards on the slab,
put some metal heat spreader plates on top and fit the pipes into the
plates. Over this you lay timber boards followed by your finished
floor.

I have been told that the "floating floor" type is better if you want
to control the heat easily as it is far more responsive than the
traditional screed type. I guess it is more like a radiator and will
heat up./ cool down more quickly than the screed.

Having had storage heaters many years ago when the room was either
boiling hot or freezing cold, I was keen not to go down that route
again.

Does anyone have the "floating floor" type fitted on top of a concrete
floor? Is it any good? Am I worrying about the standard type
unduely?

From a cost perspective, the floating floor one is at least 3 times
the price of the solid one.

All help appreciated.

thanks

Lee.

wrote:
Hi all,

I am looking to fit underfloor heating in a room of around 40m2 in a
new extension. The floor slab is down and have plenty of room for
insulation, heating etc before we get to the finished floor level.
Looking at the polyplumb website, they seem to do 2 main types which
could be used on the ground floor on top of the slab...
1. the traditional solid floor type - ie the pipes are laid in the
screed
2. a "floating floor" type - where you lay some boards on the slab,
put some metal heat spreader plates on top and fit the pipes into the
plates. Over this you lay timber boards followed by your finished
floor.

I have been told that the "floating floor" type is better if you want
to control the heat easily as it is far more responsive than the
traditional screed type. I guess it is more like a radiator and will
heat up./ cool down more quickly than the screed.

Having had storage heaters many years ago when the room was either
boiling hot or freezing cold, I was keen not to go down that route
again.

Does anyone have the "floating floor" type fitted on top of a concrete
floor? Is it any good? Am I worrying about the standard type
unduely?

From a cost perspective, the floating floor one is at least 3 times
the price of the solid one.


Mine is solid, and yes, it takes hours to warm up.

Conversely, it takes hours to cool down.


This is a plus and a minus: in summer, the rooms stay very cool.

In winter, you need to at laest maintain the rooms a couple of degrees
only lower than you need when you use them.


My biggest mistake was calculating on a steady-state basis how much pipe
I needed,. I went for 50W/sq meter. In very cold conditions this is a
VERY long warm up time.

In the corridoor, where a LOT of pipes run VERY close together, warm up
times are much better. ~200W/sq meter estimated.

So if you really lay in huge amounts of pipe, and have a suitably high
peak output boiler, you can get very fast warm up times indeed. BUT
beware the overshoot..where temps rise above the stat and go on
rising..leading to SWMBO opening the windows..;-)

There is something to be said for high thermal mass/steady temperature
versus low thermal mass/fast heat response: its really down to the use
the room will be put to. If its a living area in constant use, go for
high mass. If its a bedroom or workroom, often not occupied, go lower.

Oh, and all you NEED from polyplumb is the pipe, pump and manifold
stuff, and maybe some zone valves. In screed I laid a grid of rebar, and
tie wrapped the pipes to that. If I were making eg. a wood floor up, I
would screed, lay joists on top, insulation between, and use notched
bits of timber or bits of insulation to hold the pipes in place. Celotex
in partiucular is foil coated and reflects radiant heat.

These clever ways to lay pipes fast have application in a commercial fit
where stupid monkeys don't cost peanuts, but in a DIY context, pipe
laying is merely a matter of ensuring the pipes stay in a reasonable
relation to each other.

You should b able to fit a solid wood floor over the above, and provided
you stick to ot more tha about 40C water temp, have a very decent heatng
system. In screed you can go a bit higher, since the screed itself
'spreads the heat' but with simple pipes in an air space, the air will
circulate and do the spreading. Remember that at a given temp under the
wood floor, your watts per square meter are governed by how hot the
underside of the boards are, and what the thermal resistance of them is.
(and of course your final room temperature). There is a limit to how far
you can realistically go. I haven't calculated it myself..lemme see,
typical wood door is a U value of about 3.5, so a typical floor board
might be twice that..say 7..watts per square meter per degree C. So to
get 100W/sq meter you need at least you need 14C drop..from a room at
say 20C, thats 34C..and then you need to allow for carpets and rugs..

well its doable, but not exactly far from the limits. Which is why a
tiled screeded floor can produce more heat output..












All help appreciated.

thanks

Lee.

On 11 Nov, 13:18, wrote:
Hi all,

I am looking to fit underfloor heating in a room of around 40m2 in a
new extension. *The floor slab is down and have plenty of room for
insulation, heating etc before we get to the finished floor level.
Looking at the polyplumb website, they seem to do 2 main types which
could be used on the ground floor on top of the slab...
1. the traditional solid floor type - ie the pipes are laid in the
screed
2. a "floating floor" type - where you lay some boards on the slab,
put some metal heat spreader plates on top and fit the pipes into the
plates. *Over this you lay timber boards followed by your finished
floor.

I have been told that the "floating floor" type is better if you want
to control the heat easily as it is far more responsive than the
traditional screed type. *I guess it is more like a radiator and will
heat up./ cool down more quickly than the screed.

Having had storage heaters many years ago when the room was either
boiling hot or freezing cold, I was keen not to go down that route
again.

Does anyone have the "floating floor" type fitted on top of a concrete
floor? *Is it any good? *Am I worrying about the standard type
unduely?

From a cost perspective, the floating floor one is at least 3 times
the price of the solid one.

All help appreciated.

thanks

Lee.

Dear Lee
I echo all that the NP has said.
I would add the following things
a) I personally found for my ground floor living rooms that it is best
to have high thermal capacity with a low input temperature (I use a
heat pump at between 25 and 33 C max for my input temp) and live with
the resultant slow heat up and slow down times which do not
inconvenience me at all. If - as is the case - SWIMBO complains that
it is too hot sometimes and too cool others (when it is exactly the
same temp!) I merely say put on the thermostatically controlled
electric heater for a quick blast.
b) I would never in a month of Sundays use a wooden floor - it would
have to be ridiculously thin for the heat to get through quickly and
is a contradiction in terms laying what is effectively an insulant
between the heat source and the room (OK before the Pedants all reply
I am well aware that it can be done but it is clearly better to have a
conductor as a floor surface). I used tiles and if it is a living room
you can use slabs like York Stone or the like wiht the occassional
thin rug
c) I used Kestrin for my design and found them superb - material and
service wise but if price is the be all and end all then you have
little option but to DIY the design. Kestrin use Uponor products and
larger pipes (22mm) at about 150 cc which we have found to be fine


chris

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember saying
something like:

Does anyone have the "floating floor" type fitted on top of a concrete
floor? Is it any good? Am I worrying about the standard type
unduely?

I fitted one of those seven-ish years ago and it was cracking. Heated up
fairly quickly and cooled down reasonably so, so you avoid the boiling
storage heater effect you describe. Approx 60sq metres of flooring,
heating a barn conversion. German in origin, iirc. You must rememember
to stuff underneath the spreader plates with rockwool.

From a cost perspective, the floating floor one is at least 3 times
the price of the solid one.

That's the rub - it's not cheap, but it's effective. On balance I'd
deffo go for the floating floor heat spreader type as it's a one-off
cost and you'll be glad you did.

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember ConfusedCarbuyer
saying something like:

b) I would never in a month of Sundays use a wooden floor - it would
have to be ridiculously thin for the heat to get through quickly and
is a contradiction in terms laying what is effectively an insulant
between the heat source and the room (OK before the Pedants all reply
I am well aware that it can be done but it is clearly better to have a
conductor as a floor surface).

Wood is only a partial insulator and every bit heat under it will get
through eventually.

ConfusedCarbuyer wrote:
On 11 Nov, 13:18, wrote:
Hi all,

I am looking to fit underfloor heating in a room of around 40m2 in a
new extension. The floor slab is down and have plenty of room for
insulation, heating etc before we get to the finished floor level.
Looking at the polyplumb website, they seem to do 2 main types which
could be used on the ground floor on top of the slab...
1. the traditional solid floor type - ie the pipes are laid in the
screed
2. a "floating floor" type - where you lay some boards on the slab,
put some metal heat spreader plates on top and fit the pipes into the
plates. Over this you lay timber boards followed by your finished
floor.

I have been told that the "floating floor" type is better if you want
to control the heat easily as it is far more responsive than the
traditional screed type. I guess it is more like a radiator and will
heat up./ cool down more quickly than the screed.

Having had storage heaters many years ago when the room was either
boiling hot or freezing cold, I was keen not to go down that route
again.

Does anyone have the "floating floor" type fitted on top of a concrete
floor? Is it any good? Am I worrying about the standard type
unduely?

From a cost perspective, the floating floor one is at least 3 times
the price of the solid one.

All help appreciated.

thanks

Lee.

Dear Lee
I echo all that the NP has said.
I would add the following things
a) I personally found for my ground floor living rooms that it is best
to have high thermal capacity with a low input temperature (I use a
heat pump at between 25 and 33 C max for my input temp) and live with
the resultant slow heat up and slow down times which do not
inconvenience me at all. If - as is the case - SWIMBO complains that
it is too hot sometimes and too cool others (when it is exactly the
same temp!) I merely say put on the thermostatically controlled
electric heater for a quick blast.

We do exactly the same. The downstairs living areas are high thermal
contant, but we have open fires for a quick blast. Huge ones.

It wasn't practical to fit UFH upstairs really. I have fan convectors
and teh odd radiator in bathrooms etc etc.

WE seldom heat them at all...the UFH ges upwards nicely. And ou dint
need them to be that warm. Currently SWMBO hits the 'one hour boost'
button a half hour before a shower..




b) I would never in a month of Sundays use a wooden floor - it would
have to be ridiculously thin for the heat to get through quickly and
is a contradiction in terms laying what is effectively an insulant
between the heat source and the room (OK before the Pedants all reply
I am well aware that it can be done but it is clearly better to have a
conductor as a floor surface). I used tiles and if it is a living room
you can use slabs like York Stone or the like wiht the occassional
thin rug

I have screed with engineering floor over.Including a foam underlay. It
ain't optimal, but it works.

A friend has uninsulated copper pipes under floorboards under tiles in
a bathroom. Accidental UFH, but works very well indeed.

The issue with using non optimal materials between pipes and riom are to
first make sure that the U value DOWNWARDS is at leats 1/10th of the U
value upwards, to achieve 90% heat transfer into the room, and secondly
that the actual U value upwards does not necessitate very high
temperatures underneath. A combined U value of much less than 7 is
probably never going to be satisfactory.

Ber in mind that much conventional thinking about flooring is predicated
on the assumption that the floor, and floor level draughts , will be the
coldest part of the room. Ergo shag pile fitted carpets, 'warm' wood,
and the like are Good Things. With UFH the reverse is true and teh more
conductive the floor, the better radiator it will make. Hence stone and
tiles are preferred.

Ive just dug out my bookie wookie.

It gives a k value for timber as 0.14, so 19mm of wood has a u value of
7.3 appx.

My engineering floor is less than that..probably 10mm so will have a
U-value of 14 or so, but the 1/8th of foam underlay - say 3mm at 0.03 or
so has a U value of about 10, bringing the overall 'to the bare wood'
value down to about 5.8, and then if you add the rugs..its no wonder I
don't get rapid heating. At 50W/sq meter I am up around 10 C over
ambient at the pipes..say 30C..or more..

Which shows overall that it isn't the wood floor that is the problem, so
much as the foam underlay and the rugs and sofa on top!


c) I used Kestrin for my design and found them superb - material and
service wise but if price is the be all and end all then you have
little option but to DIY the design. Kestrin use Uponor products and
larger pipes (22mm) at about 150 cc which we have found to be fine
I used teh polyplumb stuff, simply beca

chris


Well I used polyplumb, and frankly the pipe size and material aren't a
huge issue as long as they don't degrade in the floor! Its the manifolds
and flow valves and temp reducer that was nice with poly.

For a suspended wood floor, you might argue that copper pipe gives
better heat transfer..but the price!!

At the end of the day all a UFH system is , i a damned great radiator
laid on its side and built into the house: it needs inuslation between
it and the outside world, and good conductivity to the room its to heat,
and to be built to lats.

The rest is just about how you control the temperature inside it to
avoid breaking it.

In article
,
ConfusedCarbuyer wrote:
b) I would never in a month of Sundays use a wooden floor - it would
have to be ridiculously thin for the heat to get through quickly and
is a contradiction in terms laying what is effectively an insulant
between the heat source and the room (OK before the Pedants all reply
I am well aware that it can be done but it is clearly better to have a
conductor as a floor surface). I used tiles and if it is a living room
you can use slabs like York Stone or the like wiht the occassional
thin rug

Are you saying stone *isn't* an insulator? If so the space shuttle makers
must be told...

--
*If you try to fail and succeed, which have you done? *

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

In article , Grimly Curmudgeon wrote:
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember ConfusedCarbuyer
saying something like:

b) I would never in a month of Sundays use a wooden floor - it would
have to be ridiculously thin for the heat to get through quickly and
is a contradiction in terms laying what is effectively an insulant
between the heat source and the room (OK before the Pedants all reply
I am well aware that it can be done but it is clearly better to have a
conductor as a floor surface).

Wood is only a partial insulator and every bit heat under it will get
through eventually.

Only if you have a perfect insulator underneath will every last bit
get through eventually, otherwise some of it will be wasted going in
the wrong direction. But we have underfloor heating and a wood floor
downstairs (in most rooms), and it works. It works under carpet too.

In article , Dave Plowman (News) wrote:
In article
,
ConfusedCarbuyer wrote:
b) I would never in a month of Sundays use a wooden floor - it would
have to be ridiculously thin for the heat to get through quickly and
is a contradiction in terms laying what is effectively an insulant
between the heat source and the room (OK before the Pedants all reply
I am well aware that it can be done but it is clearly better to have a
conductor as a floor surface). I used tiles and if it is a living room
you can use slabs like York Stone or the like wiht the occassional
thin rug

Are you saying stone *isn't* an insulator? If so the space shuttle makers
must be told...

Space Shuttle tiles aren't stone.
http://en.wikipedia.org/wiki/Space_S...tem#Tile_types

wrote:

Hi all,

I am looking to fit underfloor heating in a room of around 40m2 in a
new extension. The floor slab is down and have plenty of room for
insulation, heating etc before we get to the finished floor level.
Looking at the polyplumb website, they seem to do 2 main types which
could be used on the ground floor on top of the slab...
1. the traditional solid floor type - ie the pipes are laid in the
screed
2. a "floating floor" type - where you lay some boards on the slab,
put some metal heat spreader plates on top and fit the pipes into the
plates. Over this you lay timber boards followed by your finished
floor.

I have been told that the "floating floor" type is better if you want
to control the heat easily as it is far more responsive than the
traditional screed type. I guess it is more like a radiator and will
heat up./ cool down more quickly than the screed.

Having had storage heaters many years ago when the room was either
boiling hot or freezing cold, I was keen not to go down that route
again.

Does anyone have the "floating floor" type fitted on top of a concrete
floor? Is it any good? Am I worrying about the standard type
unduely?

From a cost perspective, the floating floor one is at least 3 times
the price of the solid one.

All help appreciated.

thanks

Lee.

The floating floor you describe is very similar to the situation you
meet fitting UFCH upstairs where the pipes sit between the joists,
directly below the floorboards.
I used the PolyPlumb manifold, pump and mixer along with thier
spreader plates but with speedfit tube. The plates really do spread
the heat, they are very thin aluminium which provide a very heat-
conductive path sideways. The system responds fairly quickly and no-
one has complained about the rooms not heating up fast enough.
I fitted Celotex under the speader plates (20mm in the parts between
the tubes and 40mm under all of it). As others have said the
important thing is to control the ratio of thermal conductivity
downwards and upwards.
The plates and the Celotex helped keep the tube in place while the
boards were fitted too.

My next job is to fit my downstairs system which will be a high
thermal mass "traditional" type. Once again the trick is to have lots
of resistance downwards (lots of Celotex) and much less resistance
upwards (in my case a tiled floor because that's the finish we want
anyway). I won't be using PPs spacer system, I can see why it makes
sense for professionals for whom time is money but my time is free at
point of use and I can't see why (with a little planning and care) I
can't clip the tube to the celotex - after all it only needs to be
held until the screed sets.

As a complete OT aside I used the same principles to make an in-wall
CH radiator behind the mirror which forms one wall of my shower
cabinet. I fitted a 20mm slab of Celotex and groved it slightly to
accept 10mm Speedfit tube which runs in a double serpentine. A sheet
of ply on top and the mirror glued on to that (I got the glass company
to do that bit - I was scared!) and I have a shower wall which gives
off a little heat but more importantly which doesn't stay steamed up
for very long. It's on an inside wall so any heat getting through the
Celotex isn't wasted. You might notice there is no spreader plate
involved and it's really easy to see where the pipes are as the
condensation burns off.

Good luck with whatever you decide.

Alan Braggins wrote:
In article , Grimly Curmudgeon wrote:
We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember ConfusedCarbuyer
saying something like:

b) I would never in a month of Sundays use a wooden floor - it would
have to be ridiculously thin for the heat to get through quickly and
is a contradiction in terms laying what is effectively an insulant
between the heat source and the room (OK before the Pedants all reply
I am well aware that it can be done but it is clearly better to have a
conductor as a floor surface).
Wood is only a partial insulator and every bit heat under it will get
through eventually.

Only if you have a perfect insulator underneath will every last bit
get through eventually, otherwise some of it will be wasted going in
the wrong direction. But we have underfloor heating and a wood floor
downstairs (in most rooms), and it works. It works under carpet too.

Yes, it works. But not as well. But well enough if you can cope with not
much more than 100W/sq meter rather than say 200W/sq meter.

Calvin wrote:
wrote:

Hi all,

I am looking to fit underfloor heating in a room of around 40m2 in a
new extension. The floor slab is down and have plenty of room for
insulation, heating etc before we get to the finished floor level.
Looking at the polyplumb website, they seem to do 2 main types which
could be used on the ground floor on top of the slab...
1. the traditional solid floor type - ie the pipes are laid in the
screed
2. a "floating floor" type - where you lay some boards on the slab,
put some metal heat spreader plates on top and fit the pipes into the
plates. Over this you lay timber boards followed by your finished
floor.

I have been told that the "floating floor" type is better if you want
to control the heat easily as it is far more responsive than the
traditional screed type. I guess it is more like a radiator and will
heat up./ cool down more quickly than the screed.

Having had storage heaters many years ago when the room was either
boiling hot or freezing cold, I was keen not to go down that route
again.

Does anyone have the "floating floor" type fitted on top of a concrete
floor? Is it any good? Am I worrying about the standard type
unduely?

From a cost perspective, the floating floor one is at least 3 times
the price of the solid one.

All help appreciated.

thanks

Lee.

The floating floor you describe is very similar to the situation you
meet fitting UFCH upstairs where the pipes sit between the joists,
directly below the floorboards.
I used the PolyPlumb manifold, pump and mixer along with thier
spreader plates but with speedfit tube. The plates really do spread
the heat, they are very thin aluminium which provide a very heat-
conductive path sideways. The system responds fairly quickly and no-
one has complained about the rooms not heating up fast enough.
I fitted Celotex under the speader plates (20mm in the parts between
the tubes and 40mm under all of it). As others have said the
important thing is to control the ratio of thermal conductivity
downwards and upwards.
The plates and the Celotex helped keep the tube in place while the
boards were fitted too.

My next job is to fit my downstairs system which will be a high
thermal mass "traditional" type. Once again the trick is to have lots
of resistance downwards (lots of Celotex) and much less resistance
upwards (in my case a tiled floor because that's the finish we want
anyway). I won't be using PPs spacer system, I can see why it makes
sense for professionals for whom time is money but my time is free at
point of use and I can't see why (with a little planning and care) I
can't clip the tube to the celotex - after all it only needs to be
held until the screed sets.

As a complete OT aside I used the same principles to make an in-wall
CH radiator behind the mirror which forms one wall of my shower
cabinet. I fitted a 20mm slab of Celotex and groved it slightly to
accept 10mm Speedfit tube which runs in a double serpentine. A sheet
of ply on top and the mirror glued on to that (I got the glass company
to do that bit - I was scared!) and I have a shower wall which gives
off a little heat but more importantly which doesn't stay steamed up
for very long. It's on an inside wall so any heat getting through the
Celotex isn't wasted. You might notice there is no spreader plate
involved and it's really easy to see where the pipes are as the
condensation burns off.

Good luck with whatever you decide.


Fsscinating stuff.

I am thinking of making in wall panels myself for where the floors are
not deep enough, due to exposed beams..

Even in screed, you can see - as I discovered whne I PVA'ed mine before
levelling it, where the pipes run by the dry patches. Screed ain't a LOT
better tan wood, conduction wise.

The Natural Philosopher wrote:
Calvin wrote:
wrote:

Hi all,

I am looking to fit underfloor heating in a room of around 40m2 in a
new extension. The floor slab is down and have plenty of room for
insulation, heating etc before we get to the finished floor level.
Looking at the polyplumb website, they seem to do 2 main types which
could be used on the ground floor on top of the slab...
1. the traditional solid floor type - ie the pipes are laid in the
screed
2. a "floating floor" type - where you lay some boards on the slab,
put some metal heat spreader plates on top and fit the pipes into the
plates. Over this you lay timber boards followed by your finished
floor.

I have been told that the "floating floor" type is better if you want
to control the heat easily as it is far more responsive than the
traditional screed type. I guess it is more like a radiator and will
heat up./ cool down more quickly than the screed.

Having had storage heaters many years ago when the room was either
boiling hot or freezing cold, I was keen not to go down that route
again.

Does anyone have the "floating floor" type fitted on top of a concrete
floor? Is it any good? Am I worrying about the standard type
unduely?

From a cost perspective, the floating floor one is at least 3 times
the price of the solid one.

All help appreciated.

thanks

Lee.

The floating floor you describe is very similar to the situation you
meet fitting UFCH upstairs where the pipes sit between the joists,
directly below the floorboards.
I used the PolyPlumb manifold, pump and mixer along with thier
spreader plates but with speedfit tube. The plates really do spread
the heat, they are very thin aluminium which provide a very heat-
conductive path sideways. The system responds fairly quickly and no-
one has complained about the rooms not heating up fast enough.
I fitted Celotex under the speader plates (20mm in the parts between
the tubes and 40mm under all of it). As others have said the
important thing is to control the ratio of thermal conductivity
downwards and upwards.
The plates and the Celotex helped keep the tube in place while the
boards were fitted too.

My next job is to fit my downstairs system which will be a high
thermal mass "traditional" type. Once again the trick is to have lots
of resistance downwards (lots of Celotex) and much less resistance
upwards (in my case a tiled floor because that's the finish we want
anyway). I won't be using PPs spacer system, I can see why it makes
sense for professionals for whom time is money but my time is free at
point of use and I can't see why (with a little planning and care) I
can't clip the tube to the celotex - after all it only needs to be
held until the screed sets.

As a complete OT aside I used the same principles to make an in-wall
CH radiator behind the mirror which forms one wall of my shower
cabinet. I fitted a 20mm slab of Celotex and groved it slightly to
accept 10mm Speedfit tube which runs in a double serpentine. A sheet
of ply on top and the mirror glued on to that (I got the glass company
to do that bit - I was scared!) and I have a shower wall which gives
off a little heat but more importantly which doesn't stay steamed up
for very long. It's on an inside wall so any heat getting through the
Celotex isn't wasted. You might notice there is no spreader plate
involved and it's really easy to see where the pipes are as the
condensation burns off.

Good luck with whatever you decide.


Fsscinating stuff.

I am thinking of making in wall panels myself for where the floors are
not deep enough, due to exposed beams..

Even in screed, you can see - as I discovered whne I PVA'ed mine before
levelling it, where the pipes run by the dry patches. Screed ain't a LOT
better tan wood, conduction wise.

I must say that my aim wasn't to make a radiator in the sense that I
wasn't looking to heat the room. I was looking for a way to keep a
2m2 mirror from steaming up. In-wall heating is becoming trendy in
Germany (at least) apparently although I can't help but worry that the
wall is an obvious target for a drill... I figured that I didn't need
to worry about anyone ever drilling into mine as no-one's stupid
enough to drill into a mirror... are they?

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember (Alan
Braggins) saying something like:

Wood is only a partial insulator and every bit heat under it will get
through eventually.

Only if you have a perfect insulator underneath will every last bit
get through eventually, otherwise some of it will be wasted going in
the wrong direction. But we have underfloor heating and a wood floor
downstairs (in most rooms), and it works. It works under carpet too.

I just knew someone would pick up on that as soon as I hit 'send'.

Ok. Most.

In article ,
Alan Braggins wrote:
Are you saying stone *isn't* an insulator? If so the space shuttle
makers must be told...

Space Shuttle tiles aren't stone.

http://en.wikipedia.org/wiki/Space_S...tem#Tile_types

They are ceramic which is to all intents and purposes stone.

--
*OK, so what's the speed of dark? *

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