Hi,
John Stumbles coughed up some electrons that declared:
On Mon, 05 Jan 2009 21:56:30 +0000, Tim S wrote:
http://www.floorheater.co.uk/
Interesting. I've added a link to the Wiki UFH page
http://wiki.diyfaq.org.uk/index.php?...rfloor_Heating.
Have you priced up getting the existing floor dug out and replaced with
proper insulated slab with embedded UFH?
No - partly because the thought of the amount of work, mess and expected
cost scared me (even if I didn't do the job!). Perhaps it might be less bad
than I thought if I did price it, but it's too late now - I've made the
decision not to do that and I'm too single minded to change my mind at this
stage as work's started (which is probably a good thing IMHO with a large
project). The idea of adding any insulation to the surface was an
opportunistic one as it doesn't add much to the work and doesn't break the
basic plan. The UFH is even more opportunistic - but I'm not commited until
I prove it to not be an utterly stupid thing to do. At least the extra work
for UFL plumbing is offest by no radiator plumbing.
If I think for one minute that sticking stuff under floor tiles is going to
make them less than long lived, I'll scrap this and go back to the original
plan as robustness and longevity is a higher priority for us.
No system using thin insulation
on top of an existing uninsulated slab is going to give similar
efficiency.
Agreed. The whole thing started off due to discussion at work about how
effective 25mm of Jablite was compared to nothing. Of course, there'll be
more losses with UFL as it runs at 27C as opposed to the floor tiles
getting to maybe 18C with insulation but no UFH. There is an element of a
previous discussion suggesting losses away from the external walls may be
less due to the ground retaining some heat - I'll never calculate that
though. But a worse case calculation based on the board's k-value assuming
a certain (constant) ground temperature will be easy enough.
Plus is the existing slab properly DPCed?
No. None whatsoever. The email I got back from teh company said to use
cementous tile adhesive to stick the panels down as what they'd normally
recommend isn't very good in the damp. But I'm looking at a couple of coats
of Aquaseal (Aqua Stop IIRC) onto the concrete / screed anyway for good
measure. The floor has survived 50 years with a variety of floor coverings
including vinyl, clay tiles and wood tiles with no obvious problems so I'm
not particularly concerned. No mushrooms on the walls, though that may be
due to what looks like a chemical DPC that's been injected some time ago
(found the injection holes behind some skirting I pulled off last week).
On a job I've been working on the builders did just this - to an area of
about 7m x 3m total. Took 2 labourers about a day to dig it out, maybe
half a day to level the area with concrete, maybe another half day to lay
polythene DPC + 100m polystyrene (+ UFH piping), another day or so to
concrete. They were mixing up the concrete in a barrowmix: on a bigger job
with readymix one would obviously save some time over that.
That's interesting. The cost break point for me for 95m2 is about 2500 quid.
That is the combined cost of Marmox board (stronger jablite in effect) and
all the rads, soem vertical rads (not cheap but a necessity due to room
shapes) and a couple of Myson fan convectors (also not cheap, but
required).
I wonder why no-one's done a marmox type board based of PIR foam? Would seem
to be an obvious product, unless there's a technical difficulty... Did scan
the Celotex and Kingspan sites, but there's nothing identical in
application.
I'll come back when I have some more info from them.
Cheers
Tim