Hi, I am thinking to refurbish a first floor flat with screed floors and install water underfloor heating. I know that I have to raise floors around 10 cm but the height between floor and ceiling is just 235 cm. Has anyone had the same problem ? Would you suggest to go on with the project ?
Thank you, Mirco
I would actually.
In this case I would actually go for a raised timber floor. Less messy than screeding and you wont get away with 10cm with screed plus necessary isluation either.
I reckon 2.2m is the minimum room height..beware friends who are 6'8" tall though ;-)
If you want more than half the heat to go into your flat, not the one downstairs, use about 50mm of celotex as a minimum, or one of these proprietary foam mouldings to carry the pipes, and follow manufacturers recommendations.
Here is a typical, but by no means the only, product
Also, despite heatloss calcs, go for at least 100W/sq meter. UFH is great if you have large empty rooms that are tiled: Its a loss less effective under sofas and rugs. With a thin floor and with wood, you don't want too much local heat, so LOTS of pipes..cram them in. Its easy enough to turn UFH down, Its very hard to turn it up.
Another point: you cannot and should not go for more than about 50C outflow temps on the CH circuit. Normally this means a temp reducing valve which costs. HOWEVER consider running the whole boiler at lower temps - it will be more efficient, and if hot water needs to be hotter, use am immersion heater in the tank as well.
IF its a small flat, one thermostat is enough, and then balance individual rooms for desired result. If its large or has areas you dont use, consider zoning it.
Be prepared for very long warm-up times. Although a timber floor is vastly better than screed in this rep sect , and set any timer accordingly. This is another reason to have high pipe density..things te warmer faster.
You can roll your own proper themostatic mixing system for approx £100 with a UFH mixing valve (from Toolstation) pump and cylinder stat (or two: one as overheat cutout) and handful of fittings. Well worth the efort for a smaller installation.
DEFINETLY NOT
DONT FORGET THAT DOORS WILL ALSO BE 10cm SMALLER.
Cylinder stata? Prey tell.
No, ceiling will be too low, nobody will want to live there. Says, I, having just returned from staying at a house with 10 foot ceilings. Sadly, my house only has 8 foot ceilings, and it seems slightly oppressive to me now. I'm a shade under 6 feet tall. At 225cm, you'd be walking into light fittings. Simon.
You mean "stats" and "pray"?
One to switch the UFH pump on when the flow from the boiler is hot enough to be worthwhile, another as an overheat to cut out the pump if the flow temperature is too high.
This is of course for a set-up where the UFH is not being run as a separate zone. Yes I know UFH takes longer to warm up so it should be a separate zone with its own time & temp controls: this is the budget system. If it is a separate zone then you just have the overheat stat, wired to close the zone valve.
So use uplighters on the walls.
Ah!! you mean pipe stats, not cylinder stats. The overheat is a backup in case the TMV fails. It still needs a room stat in case the room overheats. It needs a non-returnvalve in front of the pump to trpevent any circuoation frommthe systems primary pump. So, three stat in all, a TMV, non-return valve and a pump. .and a coil of plastic pipe and some fittings. I would say more than £100.
Best, is a heat bank using giving cheap and effective UFH using a dual temperature boiler, like the Broag, Keston and others (avoid Keston though). With dual temperature boilers with internal weather compensation, using a boiler controlled 3-way diverter valve, they can reheat the DHW store top section ASAP under full boiler heat, when heated the valve closes and it heats the lower CH section under low temperature weather compensation control - duel temperature boiler output. The rads or UFH pumps, pump this water, which is the right temperature to the heating loop(s) (zones). Using rads a Smart pump with TRVs all around can be used and no central room stat screwing up the CH air temperature control. Then no UFH TMVs as the water in store is the correct temperature set by the boilers integral weather compensator. Of couse have a high limir pipe stats on the UFH loop(s).
With low ceilings wall lights have to be used to five the impression of height. Also a smooth very white ceiling.
Tommy coughed up some electrons that declared:
Arrgh my ears!
Don't shout, mate...
Mirco Simoni coughed up some electrons that declared:
My rooms are 2.47m floor screed to ceiling.
I am installing a layer of insulation (Marmox) leaving the finished floor about 35-40mm higher than the screed level, so about 20-30mm higher than previous floor finishes.
This is right at the limit of my door frames, having nailed a batten across the door to simulate the new opening height. Any lower and it felt claustrophobic.
Don't forget that people bounce as they walk, so standing head height clearance is not a good indicator alone.
Now, I don't know what you plan to do with your doors, but I think 10cm off a 2.35m height is going to make the ceilings horrible.
I presume you are looking at 40mm insulation and 60mm screed or variations.
Some variant solutions:
1) You can run sand/cement screed down to 10mm thick if you use an SBR modified mix. I've done this - my only problem was getting it tamped level (had to finish with some self leveller) - but my rooms were weird shapes making the use of several tamping bars necessary and the errors occurred generall where the walls changed direction.2) You can get UFH (wet) panels in polystyrene which can be glued to a subfloor (bad from heat loss POV) or glued to marmox (better) which itself can be glued to the subfloor if that's reasonably flat.
That setup is not as rigid, requiring larger format tiles, but allegedly will also take a floating wood floor.
Cheers,
Tim
Sorry, yes. Though many cyl stats can be used as pipe stats also, and that's what I've been using. Really need a bit of pipelag with an appropriate cutout to ensure the stat is really sensing the pipe temp and not ambient.
Wot I said :-)
If you're not using the UFH as a separate zone then you'd want a room stat, in the same way you'd want a TRV on a rad.
How would you fit this valve to allow circulation from the UFH pump but prevent circulation caused by the system pump?
Of course if the UFH is a separate zone its 2-port zone valve carries out this function.
I wasn't including the pipe in the price since you'd need this whether you were rolling your own UFH mixer or buying a £300+ proprietary mixer/manifold assembly.
And that would be less than £100?
Thanks Tim for spoiling my day:)
I have measured the heights of my ceilings. 2.32m upstairs on every ceiling. But downstairs they are 2.30m for the rooms at the front of the house and
2.38m for the rooms at back of the house. A quick check with two neighbours show they that have identical ceiling heights to my house.Adam
why?
even without insulation underneath you're not going to lose a lot of heat to the flat below, since that will probably have something like an air gap and plasterboard on its side of the slab (unless you're in some Eastern European cell, or perhaps Peckham :-)).
Look up the uk.d-i-y wiki's article on UFH and there are links to some thin wet UFH systems. One is just 15mm thick.
YAPH coughed up some electrons that declared:
You can get 12mm now...
With no NRV the TMV may be open and circulation into the UFH zone. It needs a positive stop to circulation. The room stat switches the pump.
Yep.
No. But a "cheap to install", fully pro, efficient, cheap to run system. Use the dual temperature boiler's controls to maximum advantage. This saves a hell of a lot on expensive, bulky UFH control, and gives mains pressure DHW that will not blow up.
The boiler maintains the UFH temp to the weather - set slope of compensator. One UFH pump can be used off the store and each UFH zone uses a cheap 2 port zone valve and room stat - simple and cheap. Or a pump for each zone from a small manifold off the store, at the store. No TMVs on zones or whatever. And the boiler is operating at a very low, highly efficient return temp all the it reheats the UFH section of the store. Even when reheating DHW is will be condensing about 80-90% of the time.
Where?
I agree with the desirability of preventing the system pump pushing water through the UFH even when the UFH pump is off. I just don't see how you can arrange a NRV to prevent the first without also preventing flow through the UFH from the UFH pump itself.
Assuming we have an arragement like this:
CH FLOW >--------- | ------ UFH | TMV |-----( > )------> UFH FLOW ------ PUMP | CH RETURN
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Mirco Simoni saying something like:
Use the alloy plate heat-spreader system and you lose no height. Under the alloy plates is packed with fibreglass or rockwool insulation.
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