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

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

Christian.

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


Stout lad!

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

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

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

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

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

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

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

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

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

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

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