I have a large room to screed at work, 75mm celotex with 75mm of screed on
top. It's for office and dry storage. Currently there's only electrcity for
heating but there's a possibility of ground source heat pump or gas heating
in the future (gas main 150 metres away but this is part of a larger
development).

Will it be worth embedding UFH pipes in the screed just in case, if so
what's the minimimum I can do now? My guess is staple pipes to celotex in 3
loops for zones and terminate them but how? I've been quoted GBP2400 for
the installation but the cost of pipes looks like GBP800.

AJH

On Sun, 21 Mar 2010 15:22:24 +0000, andrew wrote:

I have a large room to screed at work, 75mm celotex with 75mm of screed on
top. It's for office and dry storage. Currently there's only electrcity for
heating but there's a possibility of ground source heat pump or gas heating
in the future (gas main 150 metres away but this is part of a larger
development).

Will it be worth embedding UFH pipes in the screed just in case, if so
what's the minimimum I can do now? My guess is staple pipes to celotex in 3
loops for zones and terminate them but how? I've been quoted GBP2400 for
the installation but the cost of pipes looks like GBP800.

It would have to be a *very* large room to need 800 quid's worth of pipe,
even including whatever system you use for holding the pipework in place
before screeding. (You can use the sort of giant lego stuff that polyplumb
sell, but you'll probably want more than 75mm screed on top, or plastic
combs into which the pipes clip and plastic spiked 'U' clips pushed into
the insulation below, which you can get from various suppliers including
Toolstation and, IIRC, screwfix.

You will need to calculate the heatloss of the room to determine the
required heat output of the floor, and from that the pipe spacing. You
also need to do mass flow calculations to work out how many parallel loops
to divide the UFH into: much over about 10m^2 at 100mm spacing the
pressure required to drive the necessary flow of water through the
pipework gets more than you can get from a standard circulation pump.
Unfortunately the calculations involve non-linear components so you can't
simply apply a formula: you need to look up values on a graph (I have an
ancient Hepworth one, part of a cyclostyled typescript guide to UFH from
back in the 1980s!) but it's not rocket science.

Lastly you need to plan out and actually lay your pipework, which can be a
bit fun!

Altogether not a matter of a trivial 'throw a bunch of pipe onto the floor
and then screed' operation, but as you have no doubt appraised it's now or
never!



--
John Stumbles -- http://yaph.co.uk

I'm more non-competitive than you

andrew wrote:
I have a large room to screed at work, 75mm celotex with 75mm of screed on
top. It's for office and dry storage. Currently there's only electrcity for
heating but there's a possibility of ground source heat pump or gas heating
in the future (gas main 150 metres away but this is part of a larger
development).

Will it be worth embedding UFH pipes in the screed just in case,

absolutely.

if so
what's the minimimum I can do now? My guess is staple pipes to celotex in 3
loops for zones and terminate them but how? I've been quoted GBP2400 for
the installation but the cost of pipes looks like GBP800.


No need to do any more than put pipes in, however a manifold may be
useful so you can terminate/pressurise them before screeding to test,
and prevent crushing.

Lay in concentric spirals at 4" pitch. That gives a very large transfer
area - ideal if you only have warm water.


All I used was rebar mesh with the pipes tie wrapped to it. Cheap as chips.


AJH

YAPH wrote:
On Sun, 21 Mar 2010 15:22:24 +0000, andrew wrote:

I have a large room to screed at work, 75mm celotex with 75mm of screed on
top. It's for office and dry storage. Currently there's only electrcity for
heating but there's a possibility of ground source heat pump or gas heating
in the future (gas main 150 metres away but this is part of a larger
development).

Will it be worth embedding UFH pipes in the screed just in case, if so
what's the minimimum I can do now? My guess is staple pipes to celotex in 3
loops for zones and terminate them but how? I've been quoted GBP2400 for
the installation but the cost of pipes looks like GBP800.

It would have to be a *very* large room to need 800 quid's worth of pipe,
even including whatever system you use for holding the pipework in place
before screeding. (You can use the sort of giant lego stuff that polyplumb
sell, but you'll probably want more than 75mm screed on top, or plastic
combs into which the pipes clip and plastic spiked 'U' clips pushed into
the insulation below, which you can get from various suppliers including
Toolstation and, IIRC, screwfix.

You will need to calculate the heatloss of the room to determine the
required heat output of the floor, and from that the pipe spacing. You
also need to do mass flow calculations to work out how many parallel loops
to divide the UFH into:


That is unecessary. Simply don't use more than one reel per loop. If
that means more reels, use more. I would say at 4" spacing (I used 8", a
slight mistake really) you meed a loop for every 7.5 sq meters I had two
for 30 squares, and its a bit light on peak power - only about 50W/sq
meter.Thinking about that if the pipe spacing is 100mm its effectively
doing 10 meters length per square meter floor area, so that looks like a
maximum recommended pipe length of 75 meters. IIRC I had 100 meter reels
and that was the recommended maximum per loop. I get good flow through 8
(parallel) lengths like that with a standard pump.

Never join pipe either. Throw the scraps away or use them to plumb the
house elsewhere.

much over about 10m^2 at 100mm spacing the
pressure required to drive the necessary flow of water through the
pipework gets more than you can get from a standard circulation pump.
Unfortunately the calculations involve non-linear components so you can't
simply apply a formula: you need to look up values on a graph (I have an
ancient Hepworth one, part of a cyclostyled typescript guide to UFH from
back in the 1980s!) but it's not rocket science.


Too much detail. stick to 100 meter runs max and less if possible.

Lastly you need to plan out and actually lay your pipework, which can be a
bit fun!

Altogether not a matter of a trivial 'throw a bunch of pipe onto the floor
and then screed' operation, but as you have no doubt appraised it's now or
never!


It can be that simple actually. But to get the best out of limited
lengths, you need to lay in a double spiral So conceptually your hottest
flow is nearest the coldest outer wall, and the coldest return is next
to that, and you must take that double loop around till you get to the
middle where conceptually, the flow and return are joined in a rather
messy big loop. Its not good to bend the pipe too hard.


I'll add in a couple of other points: putting heating under things like
kitchen cupboards or sofas is a waste of time. The efficiency of the
whole thing is the ratio between the insulation downwards, to the cold
floor below, and the 'insulation' upwards, into the room. The more
carpets and furniture you have, the hotter the floor needs to run and
the better the insulation below has to be. UFH works best on conductive
floors like tiles, or at a pinch, wood. It suffers from rugs, and is a
disaster under thick carpets. If your idea of comfort is a fitted carpet
with underlay, forget UFH.

"The Natural Philosopher" wrote in message
...
YAPH wrote:
On Sun, 21 Mar 2010 15:22:24 +0000, andrew wrote:

I have a large room to screed at work, 75mm celotex with 75mm of screed
on
top. It's for office and dry storage. Currently there's only electrcity
for
heating but there's a possibility of ground source heat pump or gas
heating
in the future (gas main 150 metres away but this is part of a larger
development).

Will it be worth embedding UFH pipes in the screed just in case, if so
what's the minimimum I can do now? My guess is staple pipes to celotex
in 3
loops for zones and terminate them but how? I've been quoted GBP2400 for
the installation but the cost of pipes looks like GBP800.

It would have to be a *very* large room to need 800 quid's worth of pipe,
even including whatever system you use for holding the pipework in place
before screeding. (You can use the sort of giant lego stuff that
polyplumb
sell, but you'll probably want more than 75mm screed on top, or plastic
combs into which the pipes clip and plastic spiked 'U' clips pushed into
the insulation below, which you can get from various suppliers including
Toolstation and, IIRC, screwfix.

Indeed, £800 is a *lot* of plastic tube and Polypipe egg-boxes. Of course
if you're including the manifold etc then a large part of it will be that.
The Polyplumb egg-boxes (red plastic former that holds the pipe in place)
are wonderful. They are strong enough to walk on, they are easy to work,
they hold together well and they hold the pipe in just the right place. I'm
sure that it's cheaper to use re-bar and tie wraps but it can't possibly be
easier or more satisfying.


You will need to calculate the heatloss of the room to determine the
required heat output of the floor, and from that the pipe spacing. You
also need to do mass flow calculations to work out how many parallel
loops
to divide the UFH into:
That is unecessary. Simply don't use more than one reel per loop. If that
means more reels, use more. I would say at 4" spacing (I used 8", a slight
mistake really) you meed a loop for every 7.5 sq meters I had two for 30
squares, and its a bit light on peak power - only about 50W/sq
meter.Thinking about that if the pipe spacing is 100mm its effectively
doing 10 meters length per square meter floor area, so that looks like a
maximum recommended pipe length of 75 meters. IIRC I had 100 meter reels
and that was the recommended maximum per loop. I get good flow through 8
(parallel) lengths like that with a standard pump.


I'm with TNP on that, the rules say you mustn't have pipe joins in the
screed anyway and 100m is a sensible max length so laying multiple 100m runs
works just fine. If you use the PP boxes then the pipes will naturally sit
at 100mm spacing which is perfect.
If you lay at 100mm spacing you're giving yourself most flexibility. You
can always run cooler water if you've got too much heating.

Never join pipe either. Throw the scraps away or use them to plumb the
house elsewhere.

much over about 10m^2 at 100mm spacing the
pressure required to drive the necessary flow of water through the
pipework gets more than you can get from a standard circulation pump.
Unfortunately the calculations involve non-linear components so you can't
simply apply a formula: you need to look up values on a graph (I have an
ancient Hepworth one, part of a cyclostyled typescript guide to UFH from
back in the 1980s!) but it's not rocket science.

Too much detail. stick to 100 meter runs max and less if possible.

Lastly you need to plan out and actually lay your pipework, which can be
a
bit fun!

Altogether not a matter of a trivial 'throw a bunch of pipe onto the
floor
and then screed' operation, but as you have no doubt appraised it's now
or
never!

It can be that simple actually. But to get the best out of limited
lengths, you need to lay in a double spiral So conceptually your hottest
flow is nearest the coldest outer wall, and the coldest return is next to
that, and you must take that double loop around till you get to the middle
where conceptually, the flow and return are joined in a rather messy big
loop. Its not good to bend the pipe too hard.

I'll add in a couple of other points: putting heating under things like
kitchen cupboards or sofas is a waste of time. The efficiency of the whole
thing is the ratio between the insulation downwards, to the cold floor
below, and the 'insulation' upwards, into the room. The more carpets and
furniture you have, the hotter the floor needs to run and the better the
insulation below has to be. UFH works best on conductive floors like
tiles, or at a pinch, wood. It suffers from rugs, and is a disaster under
thick carpets. If your idea of comfort is a fitted carpet with underlay,
forget UFH.


Having done it I can confirm it's one of those jobs which appears to be
complex because all of the literature and lots of the people like to make it
sound "special". In reality it's trivial - it really is that easy.
The only thing I've not seen mentioned here so far and which really does
matter is that the pipe must be pressurised during the screeding and must
remain so while the screed goes off. This is important because the pipe
expands ever so slightly when filled with hot water and screed doesn't like
that. By pressurising during screeding you ensure there is space for that
expansion without cracking the screed.

Calvin Sambrook wrote:

The only thing I've not seen mentioned here so far and which really does
matter is that the pipe must be pressurised during the screeding and must
remain so while the screed goes off. Â*This is important because the pipe
expands ever so slightly when filled with hot water and screed doesn't
like that. Â*By pressurising during screeding you ensure there is space for
that expansion without cracking the screed.

How is it normally pressurised, compressed air?

Does the manifold have to sit in the screed or can the pipe be terminated
and left above the screed and manifold fitted later?

I confess I have never seen an UFH installation.

AJH

On Sun, 21 Mar 2010 21:52:24 +0000, andrew wrote:

How is it normally pressurised, compressed air?

Noooo!

Just connect to mains water: it'll be higher pressure than the UFH will
normally run at. (If the mains were stupidly high, like 6-7 bar, rather
than the 3.5 bar that's typical round here, I'd pressurise to less.)

Does the manifold have to sit in the screed or can the pipe be terminated
and left above the screed and manifold fitted later?

The manifold is external. If you're just putting in the pipework for
future-proofing you don't need to bother with a manifold until when/if you
want to use the system.



--
John Stumbles -- http://yaph.co.uk

Pessimists are never disappointed

On Sun, 21 Mar 2010 18:30:24 +0000, The Natural Philosopher wrote:

No need to do any more than put pipes in, however a manifold may be
useful so you can terminate/pressurise them before screeding to test,
and prevent crushing.

A manifold is expensive if you're not going to use it yet: get a bagful of
speedfit, join it all together and pressure up from the mains. Re-use the
speedfit afterwards!



--
John Stumbles -- http://yaph.co.uk

Time flies like an arrow
Fruit flies like a banana
Tits like coconuts

On 21 Mar 2010 23:38:39 GMT, YAPH wrote:

The manifold is external. If you're just putting in the pipework for
future-proofing you don't need to bother with a manifold until when/if
you want to use the system.

But it might be worth checking the layout of the flows/returns on the
maifold so the pipes can come out of the floor in a sensible order in
relation to where they need to be in the floor and to connect to the
maifold. But that could just be my dislike of "rats nests". B-)

--
Cheers
Dave.

On Sun, 21 Mar 2010 21:52:24 +0000
andrew wrote:

Calvin Sambrook wrote:

The only thing I've not seen mentioned here so far and which really does
matter is that the pipe must be pressurised during the screeding and must
remain so while the screed goes off. Â*This is important because the pipe
expands ever so slightly when filled with hot water and screed doesn't
like that. Â*By pressurising during screeding you ensure there is space for
that expansion without cracking the screed.

How is it normally pressurised, compressed air?

Does the manifold have to sit in the screed or can the pipe be terminated
and left above the screed and manifold fitted later?

I confess I have never seen an UFH installation.

AJH

I filled mine with water and pressurised it to 8 bar with a
Rothenburger pump. This was through the manifold as a connections
test. Manifold about a metre above the floor, watch out not to kink
the pipe as it goes through the 90 deg. to the floor - smooth curve
former recommended. After an hour I lowered the pressure to 6 bar until
after the screed was laid. The pressure protects against builders boots
as well as kinks and makes sure the screed doesn't crack. The pressure
was removed 24 hours after the screen was laid. Screed finished with
travertine. 3 years later, still in love with my floor, sometimes I lay
down and cuddle it.

R.

In message , andrew
writes
Calvin Sambrook wrote:

The only thing I've not seen mentioned here so far and which really does
matter is that the pipe must be pressurised during the screeding and must
remain so while the screed goes off. *This is important because the pipe
expands ever so slightly when filled with hot water and screed doesn't
like that. *By pressurising during screeding you ensure there is space for
that expansion without cracking the screed.

How is it normally pressurised, compressed air?

I didn't pressurise mine. 85mm of dryish screed though. No signs of
cracking or other problems... yet:-)

Does the manifold have to sit in the screed or can the pipe be terminated
and left above the screed and manifold fitted later?

I put the manifold on the wall behind what may be some kitchen units.

I confess I have never seen an UFH installation.

I have some photos. I opted for 200mm spacing as there did not seem much
likelihood of future heat pump water.

My mistake was in allowing a plumber to lay the *eggshells* and do an
initial pipe layout. In a single space there should not be a problem but
the *interlocking* nature of the pipe spacers prevents one from doing
two rooms and expecting a neat lap where they meet.

As TNP says, you must use the 100mm spacing in a double helix for the
low water temperatures of green heat and don't try to turn plastic pipe
in 100mm for the final loop. Use flexible ducting where the pipes enter
the screed and when going through walls. I found doing a paper trial
layout essential.

regards
--
Tim Lamb

andrew wrote:
Calvin Sambrook wrote:

The only thing I've not seen mentioned here so far and which really does
matter is that the pipe must be pressurised during the screeding and must
remain so while the screed goes off. This is important because the pipe
expands ever so slightly when filled with hot water and screed doesn't
like that. By pressurising during screeding you ensure there is space for
that expansion without cracking the screed.

How is it normally pressurised, compressed air?

water.


Does the manifold have to sit in the screed or can the pipe be terminated
and left above the screed and manifold fitted later?


Mo, pipes 'emerge' from the screed and manifold sits in your CH arae or
in a cupboard or something.

I confess I have never seen an UFH installation.


I could post pics I suppose.

AJH

YAPH wrote:
On Sun, 21 Mar 2010 21:52:24 +0000, andrew wrote:

How is it normally pressurised, compressed air?

Noooo!

Just connect to mains water: it'll be higher pressure than the UFH will
normally run at. (If the mains were stupidly high, like 6-7 bar, rather
than the 3.5 bar that's typical round here, I'd pressurise to less.)


I hired a pump for a few days and put it at 10 bar.


Does the manifold have to sit in the screed or can the pipe be terminated
and left above the screed and manifold fitted later?

The manifold is external. If you're just putting in the pipework for
future-proofing you don't need to bother with a manifold until when/if you
want to use the system.


Except its hard to pressurize without it.

YAPH wrote:
On Sun, 21 Mar 2010 18:30:24 +0000, The Natural Philosopher wrote:

No need to do any more than put pipes in, however a manifold may be
useful so you can terminate/pressurise them before screeding to test,
and prevent crushing.

A manifold is expensive if you're not going to use it yet: get a bagful of
speedfit, join it all together and pressure up from the mains. Re-use the
speedfit afterwards!



Very smart idea. Didn't think of that!

"The Natural Philosopher" wrote in message
...
YAPH wrote:
On Sun, 21 Mar 2010 21:52:24 +0000, andrew wrote:

How is it normally pressurised, compressed air?

Noooo!


Just for completeness, that's Nooooooooooooooooooooo! because it would be
bloody dangerous, you can store a lot of energy as compressed air in 100m of
15mm pipe. Sudden uncontrolled reslease of that energy would be exciting.

Just connect to mains water: it'll be higher pressure than the UFH will
normally run at. (If the mains were stupidly high, like 6-7 bar, rather
than the 3.5 bar that's typical round here, I'd pressurise to less.)

I hired a pump for a few days and put it at 10 bar.


No need to hire a pump. Screwfix and others sell a "dry pressure test kit"
for about £20, essentially it's a 15mm Speedfit with a Schreader valve and a
pressure meter. You fill the pipe with water (easiest is to flush it
through from the mains) then connect the ends together with a 15mm T with
the pressure test kit on one leg of the T. Pump it up with a bike pump and
you can hold it at any pressure you want.
The more air you leave in the pipe the more you have to pump and the more
control you have over the pressure.


Does the manifold have to sit in the screed or can the pipe be
terminated
and left above the screed and manifold fitted later?

The manifold is external. If you're just putting in the pipework for
future-proofing you don't need to bother with a manifold until when/if
you
want to use the system.

Except its hard to pressurize without it.


Easy, see above.

Polyplumb have some good photos in their brochures which should give you an
idea of how a finished installation should look.

"TheOldFellow" wrote in message
. ..

3 years later, still in love with my floor, sometimes I lay
down and cuddle it.

So do I !

Calvin Sambrook
wibbled on Monday 22 March 2010 12:00

"TheOldFellow" wrote in message
. ..

3 years later, still in love with my floor, sometimes I lay
down and cuddle it.

So do I !

Overlooking the problems hanging pictures[1], it would be an intriguing
to consider UFH in the surface of a wall, assuming the wall is either
internal or well insulated.

Seeing as someone mentioned large area low temp rads a while back. Wonder if
anyone has ever done this?

[1] If the pipe is foil coated or has a tracer, judicious use of a metal
locator...

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

"Tim Watts" wrote in message
...
Calvin Sambrook
wibbled on Monday 22 March 2010 12:00

"TheOldFellow" wrote in message
. ..

3 years later, still in love with my floor, sometimes I lay
down and cuddle it.

So do I !

Overlooking the problems hanging pictures[1], it would be an
intriguing
to consider UFH in the surface of a wall, assuming the wall is either
internal or well insulated.

Seeing as someone mentioned large area low temp rads a while back. Wonder
if
anyone has ever done this?

[1] If the pipe is foil coated or has a tracer, judicious use of a metal
locator...


Been there, done that, got one.

I saw the idea on a German manufacturer's website but I forget which one. I
used it myself alongside my shower.
One wall of my shower is constructed of a 20mm Celotex panel into which I
cut small V-shaped grooves and set into those grooves is 10mm speedfit tube.
There is a thin plywood panel on top with a large mirror as the visible
surface. It's run as a circuit off my underfloor heating.

I must admit I didn't do this in order to make a radiator, the bathroom
almost has the opposite problem of too much heat as I really want the towel
rail on to make the towels all nice and cosy even when the room is already
warm enough. With one whole wall of the shower a mirror I was looking for a
way to keep it clear of condensation. It works rather well.

In my case the problem of screwing something in to it was not an issue as
no-one would try to drill into a mirror (would they?) but I think it would
be a major issue if one were to use the same idea elsewhere.

On Mon, 22 Mar 2010 09:25:29 +0000, The Natural Philosopher wrote:

Very smart idea. Didn't think of that!

Thanks. It also just occurred to me that connecting the loops in series
with speedfit rather than in parallel via a manifold probably makes it
easier to be sure when one's got all the air out of the pipe (which you
probably want, because water at 2 or 3 bar will make the pipe really rigid
and resistant to the weight of screed or builders' barrows & boots,
whereas air at the same pressure won't). And it takes a surprisingly long
time from when you open the mains stopvalve at one end of the combined
loops to when you get water coming out of the other end!



--
John Stumbles -- http://yaph.co.uk

The ant has made himself illustrious through constant industry industrious
So what? Would you be calm and placid if you were full of formic acid?

Calvin Sambrook wrote:

No need to hire a pump. Screwfix and others sell a "dry pressure test
kit" for about £20,

against a hire of £5?

No brainer.

Tim Watts wrote:
Calvin Sambrook
wibbled on Monday 22 March 2010 12:00

"TheOldFellow" wrote in message
. ..

3 years later, still in love with my floor, sometimes I lay
down and cuddle it.
So do I !

Overlooking the problems hanging pictures[1], it would be an intriguing
to consider UFH in the surface of a wall, assuming the wall is either
internal or well insulated.

Seeing as someone mentioned large area low temp rads a while back. Wonder if
anyone has ever done this?

I've certainly considered it as an alternative to rads.

I mean heating is really crassly simple. Get something warmer than you
want the room to be, and stop the heat escaping. Its that simple.,

Radiators are perfect for aftermarket CH install like wot we did the
60;'s but why on earth are we still using them?

Heating should be built in to the structure.

a zigzag of pipework in front of rockwool and in the studwork overplated
with plasterboard, has to be a doddle to do.



[1] If the pipe is foil coated or has a tracer, judicious use of a metal
locator...


wont work on plastic pipe. BUT if the wall is warm assume its ALL pipe.


And find the coldest spot with an IR thermometer.