HI,

I was wondering about retro-fitting underfloor heating to my house and
am interested to know peoples opinions about the practicality of
this ?  The house was built in 1980 and has a concrete floor
downstairs and normal chipboard on beams for the top floor.  Is it a
practila matter to chip away channels in the concrete and run the
pipes in those then re-screed over the top ?  Any ideas about how much
that might cost for 50 sqm of downstairs floor area ?  Also, I've
heard references to the amount of insulation being needed below the
heting pipes,  would a 1980s house have been built with enough below
the floor ?  How does this apply to the top floor ?

Thanks,

Mike

"Mike"  wrote in message 
news:be4c6558-f52c-459c-bc0a-8c327b66fb6d@25g2000hsx.googlegroups.com...
> HI,
>
> I was wondering about retro-fitting underfloor heating to my house and
> am interested to know peoples opinions about the practicality of
> this ?  The house was built in 1980 and has a concrete floor
> downstairs and normal chipboard on beams for the top floor.  Is it a
> practila matter to chip away channels in the concrete and run the
> pipes in those then re-screed over the top ?  Any ideas about how much
> that might cost for 50 sqm of downstairs floor area ?  Also, I've
> heard references to the amount of insulation being needed below the
> heting pipes,  would a 1980s house have been built with enough below
> the floor ?  How does this apply to the top floor ?

There are foam slabs with built-in grooves for the pipes to lay over an 
existing floor.  See Speedfit and Polyplum for the kits.

Best draughtproof your house and pack it with insulation - 15-18 inches in 
the loft. Seal the loft with a silicon gun.  Sealed hatch door.  Insulated 
outer doors. underground insulation against the foundations. Then no need 
for UFH.

On 7 Aug, 19:50, Mike  wrote:
> HI,
>
> I was wondering about retro-fitting underfloor heating to my house and
> am interested to know peoples opinions about the practicality of
> this ?  The house was built in 1980 and has a concrete floor
> downstairs and normal chipboard on beams for the top floor.  Is it a
> practila matter to chip away channels in the concrete and run the
> pipes in those then re-screed over the top ?  Any ideas about how much
> that might cost for 50 sqm of downstairs floor area ?



No, daft idea. You need a good slab of insulation under the pipes to
minimize heat loss into the ground. Your channel plan would lose heat
sideways and then into the ground.

>  Also, I've
> heard references to the amount of insulation being needed below the
> heting pipes,  would a 1980s house have been built with enough below
> the floor ?  How does this apply to the top floor ?

No, probably none at all.

The other problem is the hest output per sq. m. is limited and because
the wall and glazing insulation isn't so good in old houses, you can't
get adequate heat out of UFH without having the floor surface too hot.

Thanks for the replies,  I alsoi am curious about UFH for the first
floor which is a normal wooden (chipboard) floor suspended on beams.
Is there any way of retro-fitting UFH to this type of floor ?

Thanks,

Mike

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

>Thanks for the replies,  I alsoi am curious about UFH for the first
>floor which is a normal wooden (chipboard) floor suspended on beams.
>Is there any way of retro-fitting UFH to this type of floor ?

If you want to do it properly, you'd have to lift the flooring and put
down 6" of insulation, then heat spreader plates, lay the pipes in, then
lay the floor again.
A quick and dirty way of doing it would be to use pre-routed boards [1],
lay them on top of the existing floor, lay the pipes in and cover them
with more chipboard. You have to be bloody careful you don't drive a
screw through a pipe, but that's a normal concern for this type of UFH.
You'd nearly treble the weight of the floor though and lose at least
1.5" of height, necessitating cutting your door bottoms, etc.

[1] Instead of pre-routed boards, you could clip the UFH pipe to the
existing floor in the necessary pattern and then fill in with chipboard.
-- 
Dave
GS850x2 XS650 SE6a

"It's a moron working with power tools.
 How much more suspenseful can you get?"
 - House

Mike wrote:
> Thanks for the replies,  I alsoi am curious about UFH for the first
> floor which is a normal wooden (chipboard) floor suspended on beams.
> Is there any way of retro-fitting UFH to this type of floor ?
> 
> Thanks,
> 
> Mike
Sue. Rip it up lay poly or other insulation between joists, and pipe 
over..then re-floor it.

Thanks for the replies.  Is it normal for UFH for each floor to have a
single giant heating pipe circuit or is it more normal for each room
to have its own set of pipes and temperature controlled valves,  kind
of like a big underfloor radiator per room ?

Thanks,

Mike

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

>Thanks for the replies.  Is it normal for UFH for each floor to have a
>single giant heating pipe circuit or is it more normal for each room
>to have its own set of pipes and temperature controlled valves,  kind
>of like a big underfloor radiator per room ?

Have a look here...

http://www.earthnrg.co.uk/ufh-principles.php

Basically, the second part of your question is the answer - each room is
a seperate entity, connected back at the manifold, but part of the zone.
There's a limit to the size of the individual loops - about 15~20sqM, so
a bedroom generally won't push the limit. Small rooms may be combined,
as you suggest above.
Each zone would be fed from and back to a manifold, the supply to each
manifold being controlled by a zone valve to suit time of day, demand
for heat from stat, etc. Within the zone would be the downstairs rooms
or the upstairs bedrooms, and so on. The return water from the UFH zones
is blended with the incoming hot water to cool it to an acceptable
temperature for UFH.

There's no limit to how much control you put on it - you could have, if
you wanted, individual control of bedroom temperature, with the addition
of stats and zone valves for each room, but that's a bit overkill.
I've never tried a thermostatic valve on the input to a room UFH, but I
see no reason why it wouldn't work - just a question of mounting the
valve with an input pipe to and from it.

It's a very effective system and perfectly suited to lower-temp inputs
like ground heat recovery or solar heat banks, but running it off an oil
or gas boiler can be expensive - not that it needs to be pricey, just
that it can be.

I'm thinking of one I did a couple of years ago - 60sqM of UFH in a barn
conversion - cost an arm and leg to run over the winter, but the owner
was pushing 90 and felt the cold. It was a beautiful job, but there was
nothing I could do if he insisted on having it on all the time. Besides,
the old bugger was loaded and could well afford it.
-- 
Dave
GS850x2 XS650 SE6a

"It's a moron working with power tools.
 How much more suspenseful can you get?"
 - House

Mike wrote:
> Thanks for the replies.  Is it normal for UFH for each floor to have a
> single giant heating pipe circuit or is it more normal for each room
> to have its own set of pipes and temperature controlled valves,  kind
> of like a big underfloor radiator per room ?
> 
> Thanks,
> 
> Mike
No normal really.

You can do it anyway you want.

"Grimly Curmudgeon"  wrote in message 
news:g81q7p$vol$1@registered.motzarella.org...
> We were somewhere around Barstow, on the edge of the desert, when the
> drugs began to take hold. I remember Mike 
> saying something like:
>
>>Thanks for the replies.  Is it normal for UFH for each floor to have a
>>single giant heating pipe circuit or is it more normal for each room
>>to have its own set of pipes and temperature controlled valves,  kind
>>of like a big underfloor radiator per room ?
>
> Have a look here...
>
> http://www.earthnrg.co.uk/ufh-principles.php
>
> Basically, the second part of your question is the answer - each room is
> a seperate entity, connected back at the manifold, but part of the zone.
> There's a limit to the size of the individual loops - about 15~20sqM, so
> a bedroom generally won't push the limit. Small rooms may be combined,
> as you suggest above.
> Each zone would be fed from and back to a manifold, the supply to each
> manifold being controlled by a zone valve to suit time of day, demand
> for heat from stat, etc. Within the zone would be the downstairs rooms
> or the upstairs bedrooms, and so on. The return water from the UFH zones
> is blended with the incoming hot water to cool it to an acceptable
> temperature for UFH.
>
> There's no limit to how much control you put on it - you could have, if
> you wanted, individual control of bedroom temperature, with the addition
> of stats and zone valves for each room, but that's a bit overkill.
> I've never tried a thermostatic valve on the input to a room UFH, but I
> see no reason why it wouldn't work - just a question of mounting the
> valve with an input pipe to and from it.
>
> It's a very effective system and perfectly suited to lower-temp inputs
> like ground heat recovery or solar heat banks, but running it off an oil
> or gas boiler can be expensive - not that it needs to be pricey, just
> that it can be.
>
> I'm thinking of one I did a couple of years ago - 60sqM of UFH in a barn
> conversion - cost an arm and leg to run over the winter, but the owner
> was pushing 90 and felt the cold. It was a beautiful job, but there was
> nothing I could do if he insisted on having it on all the time. Besides,
> the old bugger was loaded and could well afford it.
> -- 
> Dave
> GS850x2 XS650 SE6a
>
> "It's a moron working with power tools.
> How much more suspenseful can you get?"
> - House

A Keston Qudos boiler with integral outside weather compensation can be 
used.  Have a primary loop top the manifold(s). Have a high limit stat on 
this loop, set to 55C to protect the UFH pipes.  Then set the weather 
compensator curve to give no more than 50C max and the system runs itself. 
The Keston has a directly attached cylinder stat that will run the boiler to 
maximum temperature when DHW is called.  A three-way "divertor" valve should 
be used to divert the water from the boiler to the rapid heat recovery coil 
cylinder, or DHW heat bank, preferably a direct model.  Also Keston make a 
combi version of the boiler.  So when DHW is called no heat to the UFH and 
instant DHW at the taps. then it reverts back to the UFH when taps are off.

The great thing about this system is that no blending valves need be at the 
manifold(s).  The manifolds can be made up of cheap 2-port zone valves 
operated by local room stats.  Or no zone valves at all and a central room 
stat or sensor) that modulates teh boiler (UFH) temperature down, or boiler 
off.  Only one pump is needed.  It is a very cheap and effective system. The 
weather compensator on the boiler ensures the right UFH temperature. 
Centrral romm temperature control or individual room or zone control.