Underfloor heating?

[malcolm]

I'm going around in circles a bit so thought I'd come on here for a bit of (relative) sanity.

I've got a single story solid brick built barn 4m by 10m with concrete floor and pitched roof that the missus wants to become a kitchen/ dining room (I thought it might have been better as a workshop myself). Building regs want me to insulate the walls and roof before I do that. Currently it is stripped out to sort some roof issues and works begin in March next year.

The floor is going to be tiled and half of it will be filled with kitchen units so radiators only possible at one end. I was wondering about underfloor heating. I already have a heating zone dedicated to that area with a room thermostat. Half thinking about digging up the concrete floor and putting underfloor heating in.

Anyone have any experience of underfloor heating and could recommend a system I could connect up the existing heating zone? Preferably on a DIY basis as my budget already exceeds any money I've actually got. Can I just lay a load of pipes from a manifold and connect them up to the existing feed and return then control with a room thermostat?

Alternatively would radiators at one end be likely to heat a reasonably well insulated room well enough?

 

[captain-destructo]

digging up the concrete floor!!!!

could you get away with 2" polystyrene and chip board on top of the existing floor?

http://www.u-heat.co.uk/50mm-floati...2-1512-p.asp?gclid=CKatzI2qlsICFfLJtAodviIAww

 

[hunter27]

Been installing heating for many years but the company I worked for did not do underfloor. Couple of years ago I did a job for a mates daughter in a newly built stone house in my mates farm yard. We put around 75mm thick (I think) kingspan on the floor then the heating pipes were fitted on this which was then screeded over. The manufacturers designed the pipe runs under floor (amount of pipe runs per room) according to the supplied plan.
The pack came with it's own pump,manifolds,actuators,mixing valve,thermostats,motorised valve and pipe.
The upstairs was a normal radiator system.
The under floor system has to be able to turn on the boiler when required.

They love it that much my mate is thinking of digging up the old farm house floors to fit it there.

Only trouble was the builders cocked up the floor levels and it all had to be dug out and re-screeded at builders cost!
Pete

 

[Wendelspanswick]

We have electric underfloor heating in the kitchen, 1200W for approximately 10m2 (kitchen is about 20m2). I was dubious at first about the cost but once you have heated all that thermal mass up it seems to retain the heat with minimal input.
We have a thermostat set to 21°C and it rarely kicks in and then only for very short periods. Mind you we have a massive wood burner in the lounge which is just off the kitchen and that belts out loads of heat.
The heating cable, which is on a mesh, was laid on the concrete floor and set in the tile cement with porcelain tiles on top. An increase of about 20mm from the concrete floor level.

 

[brightspark]

as said above u need the kit to run it. it isnt as simple as running round the pipes and conecting to flow and return of a room thermostat ,the kit costs a few hundred quid

 

[malcolm]

I can't get away with any more height on that floor. This is an old place with split levels and the floor level in the barn might be better 6 inches lower than it is. Can imagine finding an old floor or two if I dig down a bit. Probably looking at digging down a bit, some insulation, the underfloor heating, then screed.

I wouldn't be keen on electric - gas seems a lot cheaper. A lot of the aftermarket underfloor heating suppliers seem to suggest connecting up before any zone valves. I guess that must only apply if there isn't already a zone in place. Mine turns on the boiler and opens the zone valve from the room thermostat.

Any good places to buy it?

 

[brightspark]

i do the wiring on the wet systems and do the electric underfloor mats. biggest ive fitted was 9kw through a contactor and thermostat

 

[brewdexta]

I've had water based underfloor heating for about 12 years. As the house was done in phases I have 3 different constructs
1.) the downstairs house - I couldn't dig down far, solid rock and no big machines so put down 50mm of Kingspan and but the PEX pipe in the structural slab tied to A142 mesh. Downside is that it takes a long time to warm up, but it stays warm. Regulation now is 100mm below the slab. We finished this off with imported sandstone - some call them indian tiles.
2.) Downstairs adjoining barn, we could get a digger in here so layed the structural slab, put kingspan on top of this, then mesh and tied the pipe the mesh and then a 50mm screed. We finished this off with stone from a local mill demolition, the ones that were less than 50mm thick.
3.) Upstairs we ripped out all the old woodwork as it was full of woodworm so we put in a new chipboard floor, , then purpose built polystyrene tiles down with cut outs for the pipes. Aluminium plates next then the pipe pushed into the grooves. We had put battens down first and you have to cut gaps for the pipes, this allowed us to finish with oak T&G. There's a plastic vapour barrier too, I think that was over the pipes before the T&G, would have to check.

All the above need expansion gaps, we used expanded edging. You also need some over temp protection, you don't want your slab too hot.

Also, if your using geothermal you need to overspec your pipe density so you can keep the water temp down, its worth doing this anyway, easier to put in now than later

I'm currently replacing the controls with a home made version as all the commercial ones are either crap, expensive or both. I have the hardware, just writing the software.

Regards
Andy

 

[brewdexta]

main problem with the electric ones is you can't put rugs or anything directly on the floor as you get over heating. I have that in my office, I left a 600mm border so I can put cabinets around the perimeter and it does stop you dumping crap on the floor

 

[brightspark]

[

main problem with the electric ones is you can't put rugs or anything directly on the floor as you get oveIr heating. I have that in my office, I left a 600mm border so I can put cabinets around the perimeter and it does stop you dumping crap on the floor

u can put whatever floor covering and carpets u like over them once fitted http://www.warmup.co.uk/products/electric-underfloor-heating/

 

[brewdexta]

Its pretty ubiquitous now, it wasn't 12 years ago so I bought it from Velta who's UK office isn't far from me. They did the calcs for the pipe density, I installed the manifolds and all the fittings so all they had to do was turn up with the pipe, loop it in, tie it down and terminate it on the manifold. It wouldn't be difficult to do it all yourself though. You can buy the PEX pipe and manifolds from most suppliers now, even ebay. I have separate loop per room except in big rooms where I have two. Each loop has its own valve and actuator. In big rooms the heating controls tie both the actuators into one zone. The controller is one of these really annoying pictorial LCD displays so there's no language to take into account. Trouble is that you not sure what the symbols are for and the instruction are also pictorial so once you have worked it out you make a cheat sheet. Its a pain to set up and use.

So I have 2 raspberry pi's with one-wire bus controller shields on them and sensors that cost about 3 quid each. These send temp data back to a mini fanless PC which I use as a controller. This sends XML over HTTP to 16 way relay boards with an IP interface which operate the zone actuators. Its still in very prototype mode at the moment however with a bit of help from a web programmer friend I should have a pictorial representation of the house that you can click on to zoom into any room. I have all the hardware up and running, and working with messages, just need the logic now. There is commercial software like Nest but that costs money

 

[brewdexta]

[
u can put whatever floor covering and carpets u like over them once fitted http://www.warmup.co.uk/products/electric-underfloor-heating/

Interesting, the one I bought definitely said nowt on top. Or is that just a description of me

EDIT this company mentions not putting very insulating things like bean bags on top. third answer down. I think my electric matting was a screw fix special and it was meant for laminate flooring only, I shall dig out the instructions, I think I still have 'em.

 

[lchris21]

I installed a small system in a kitchen extension i built 4 years ago. Its the best thing i ever did......I loves it, and more importantly her indoors does too.......

I went for a wet system, xtratherm, screed, etc etc. I had some faffing around with my existing system. it was a Y-plan setup, but I converted it to S-plan then added an additional zone for the UFH. This was run through its own mixer/pump system controlled by a stat in the kitchen. As stated it takes a long time to warm up, but stays warm for a very long time. With a separate zone i have mine to come on in the early hours, ready for the kitchen to be warm in the mornings, this means i can have the heating on just in the kitchen only and not pay to heat the rest of the house. I did all the install, inc wiring plumbing, testing etc. Its great especially this time of year.......................also good when you come in with wet clothes / boots on, just dump em on the floor and happy days they are dry in an our or two

 

[julianf]

I know nothing about gas boilers, but...

If youre going for wet underfloor heating, try and work out a way for your boiler to run in full condensing mode.

Most boilers only work in condensing mode as theyre heating up, which is a bit of a nonsense really, but, with UFH, your surface area is large enough to be able to run the fluid cooler, and hence, if you can figure out how to do this without wrecking the rest of your setup, youll see some efficiency gains.


Ive not done UFH here yet but, when i do, ill just get a whole load of PEX, and peg it down somhow. Im too much of a cheapskate to pay crazy money for a 'kit'.

 

[brewdexta]

You can get condensing boilers designed for low temp outputs, however I believe all they do is internalize the mixing valve you get as an add on. If you have mixed radiator and UFH system then your underfloor typically wants a lower temp than your rads so you need some way of mixing it down before it hits your UFH, something like these.

 

[Malvern]

From your dimensions a radiator at the one end is only going to give you uneven heat in the room and you'll be disappointed! You could put a kick space heater under the kitchen units at the other end but I wouldn't recommend it, in fact I always try to talk my customers out of this! Horrible things.
To put underfloor heating in properly you will need a minimum of 75mm Kingspan, or equivalent. The pipe work can't be connected to an existing circuit as it needs to work independently of the existing circuits and controlled by its own thermostat. It will need its own manifold, the manifold includes a mixing valve and pump.
The good news is most u/f manufactures will do all the calcs and drawings for you and then supply the whole kit.
The even better news is out of the many systems I've installed everyone loves the comfort and running costs of u/f heating.
PM me if you need any more info.
Martin

 

[mike os]

ufh os fairly simple...
As you have no insulation in the floor and are installing UFH building regs come into play and you have to do it right (with all the other work you are not going to get away without )

100mm concrete slab on suitable DPM ( may need Radon, ask building control) on 50 sand blinding on min 15o compact hardcore
100mm kingspan under or over floor slab, (I prefer over as easier with pipework install) with minimum 25mm perimeter insulation (under takes longer to heat up and slower to cool because of the greater mass)
get a kit for the pipework, polypipe and Nuheat will both design for you and supply a complete kit, usually in 50- 75mm sand cement screed

kits are complete with controls and motorised valves, blending valve, and room stat

don't put under units

 

[Kayos]

Condensing boilers only really condense when they are up to temp, as it's the difference in the flow and return temp that puts it in condensing mode.

As said previously, single room add on kit is best bet, they are available for various size rooms, they have a mixer valve to maintain the correct temp

 

[julianf]

Condensing boilers only really condense when they are up to temp, as it's the difference in the flow and return temp that puts it in condensing mode.

I generally try not to disagree with people, but...

Its something like 62c. If the heat exchanger is above that temperature, the vapor does not condense. If its below that temperature, the vapor condenses, and releases its state change energy.

If the exchanger is above the magic number, the water stays as a vapor, and the boiler is no longer condensing.

If you plumb it such as the secondary exchanger (again, im talking oil - i dont know how gas are configured) takes the return, and the return is below the temperature at which water condenses, then the exchanger will condense, but, again, it will do this at any temperature up to the magic number.

 

[mike os]

Ufh typically runs sub 30c