Underfloor heating

[anthony james]

I think I'm going to be spending a lot of time on this group over the next few years! Good info so far.

We're refurbing a large (24m2) kitchen which I suspect has a timber joist floor (a laminate floor is currently laid on top and we have not yet investigated but this is most likely - there is a small possibility the floor may be screeded). I want to lay tiles or natural stone of some kind but SWMBO is concerned about it being cold. The heating in the room is all at one end at the moment and it's cold in there anyway so we need to do something different. Naturally i'm interested in underfloor but know little about it.

My thought was for hot water based linked to the existing central heating system which runs off a Keston K130 running sealed CH. A QS friend has been advised that electric is the way to go for retrofits but having such an efficient CH system this seems wrong to me.

I've done a search here and picked up ref's to polypipe and i've contacted them but other ideas would be useful.

AJ

[Andy Hall]

We have a slate floor on concrete in our kitchen, conservatory, hallway, cloakroom. It is not cold underfoot at all even with no heating. This is in a reasonably modern house. In an older property with suspended floor or a damp solid floor, the story might be different.

In one sense your friend is right - electric may be easier to install, and for a smaller bathroom area can be a good way to go. For a larger area, it is going to be expensive to run, especially if you want it to provide a substantial amount of heat to the room.

It is certainly possible to do water based UFH, although if the floor is suspended, insulation needs to go underneath with pipework above that - just putting in pipes will lead to a lot of energy wastage. Specific controls are required for UFH pipework, because it needs to be run at a lower temperature than conventional heating. These are readily available, however.

.andy

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[Richard]

Install an Aga or Rayburn equivalent cooker. Ditch the Microwave and do some real Range cooking . The warmth of a continuous cooker keeps the kitchen at a welcoming temperature and there is then no need for any extra heating at all . Richard.

[Andy Hall]

I would endorse that idea as well.

(He said munching his lunch of Aga toast with Gentlemen's Relish...) :-)

.andy

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[Huge]

And for the summer, you can get a nice Swedish girl with a bucket of water and some birch twigs.

[Andy Hall]

Not a problem.

As far as the Swedish girl is concerned, sauna you than me.....

.andy

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[IMM]

There is unwelcome extra heating summer tho. Get yourself a proper modern range with modern controls that doesn't sweat the kitchen out in summer.

[RichardS]

I'd wondered about this as well - using UF in the kitchen as a secondary "comfort" heating rather than primary room heating.

However, I have been reading about heat pumps as a means of achieving this rather than electric elements or centrally heated wet supply.

Does anyone have any experience as to the economics or practicalilty of this? Do all systems rely upon a refrigerant in the pipes or can they also use plain water pumped around to utilise the seasonal ground temperature phase lag?

cheers Richard

-- Richard Sampson

email me at richard at olifant d-ot co do-t uk

[Andy Hall]

There's nothing improper about an Aga and the controls are built in.

I'm not going to repeat the same debate that has been had numerous times before because the content and the points haven't either.

.andy

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[The Natural Philosopher]

Polyplumb.

Even if you don't use their bits (IMM will immediately rubbish them, but my system is now towo years old and hasn't missed a beat) they have a lot of design stiff.

Electric is expensive to run, unless you only heat at night on lo rate.

Water is a bit more complex, and will require you to lay new screed. It is fabulous with tiled sufaces tho.

The key siiuse are laying teh correct pipe at teh correct spacing - ypu probably need to aim for 50W/sq meter for decent insulated rooms, or up to 3 times that for not. Pipe is relatively cheap compared with teh screeding ind finishing you will apply, so put plenty in.

You have to have a separate pump to pump warm - not hot - water round the special barrier pipe, and a temp reducing valve to get the water down to sensible temps. Again polyplumb do a kit of pump, manifold, motorised valve temp reducer and all ancillary bits, and its very easy to wire up.

You will need some form of separate zone control and some form of relay to get CH boiler running on UF demand, without e.g. HW demand causing the UF pump to spin up.

Think a bit about thermostat siting - you can get radio ones, but cables may be useful. If in doubt and a major refurb run lots of thermostat cables, and consider multiple zones. The polyplumb manifolds allow motorised valves to be applied to any or all zones, but it gets expensive, and IMHO not worth it - one or at most two zones with master thermos is adequate.

[The Natural Philosopher]

Better still, install both...

[The Natural Philosopher]

Nah, just do what we did, and get the aga with teh electric cooker bolted on the side...

>

[The Natural Philosopher]

I am pretty sure that at some level a refrigerant is needed, because teh majority of heat is dumped by turning the gas into a liquid, and cooling by letting it expand back to a gas. Or something. You need a liquid that will do a phase change at around teh temps and pressures you can practically hold to. If its a nuclear recator, sodium gas is indicated. Wtare is fine, if you are thinkingh of running at a few hundred centigrade and pressures of several atmospheres...but I'd stick to refrigeraant.

Having read other peoples commenst, the simple solution if its only one room and its big enough is an aga and a separate electric cooker, and

*insulate the floor well* If suspended, dig up and out, and lay screed floor over insulation. You CAN UF it as well at that stage., but with an aga in a well insulated kitxchen, I actually have the UF almost permanently off in there. Only in very cold spells is it needed. Aga bleeds 600W continuously. More when cooking. I've got slate over 4" screed over 2" polystyrene over supspended concrete block and beam floor. The floor is only cold near the outside of the house - near the aga its warm to touch, so the insulation DOES work.

Aga with electric cooker is BIG, and cots over 6 grand, plus installation of oil or gas etc. But its a nice beast, cooker and room heater combined, and very much recommended if it suits the lifestyle and cooking style.

As is inuslation, insulation and insulation! And extractor fans!

[Andy Hall]

So what do you do for flagellation??

.andy

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[PoP]

Sorry Andy, not wishing to pick you out on a personal level as I'm sure you will understand......

The same sort of comment has been made several times previously with regard to "....do a search on google to find previous comments....etc".

I'm wondering whether it might be appropriate to have a web site (or at least a web page) showing links to appropriate articles, so that the next time someone asks about using a doodah whatsit for their gaga-confangled installation they can be referred to an appropriate resource, rather than be given the brush-off by responding with "search google!"?

Perhaps this "general" idea can be discussed further?

PoP

[IMM]

How about ripping out the bathroom and having a tin bath in front of the fire as well.

[IMM]

Madness!

Then he goes on to say dig out the floor just to put in a 1930s piece of cast iron. Madness, total madness!!

[IMM]

I am not rubbishing the, Gledhill do. The only makers I know who specifically mention a particular plastic maker. BEWARE!!!

Look at Speedfit, they do something similar.

[IMM]

There is an FAQ, which if many had read they would not be asking the Qs they do.

[The Natural Philosopher]

Whatever for? Neither stylish nor comfortable.

Nutcase.