Blocking UFH heat

[divorcingjack]

Hi all,

 

I've got a bit of a UFH dilemma which I need to try and resolve pretty quickly to meet materials ordering deadlines. We have a large kitchen/dining/living room downstairs. The architect and us have different opinions on where the kitchen island/units should be. We're pretty convinced on our placing, but the architect has proven himself correct on many occasions and I'm aware of the possibility of having to move the kitchen when the frame goes up.

 

Unfortunately, by this point, the UFH pipes will be in the slab, so we are left with the possibility of an unheated area where we wanted the island, and a warm bin in the new position. So, my question is - if there are UFH pipes under a kitchen island, will putting down a sheet of insulation on top (in the base of the units) or a high tog carpet block the heat enough? Will it overheat/damage the UFH?  We looked at trying to have the island locations as separate loops but it was really complicated.

 

The build is MBC passive slab and frame, so very airtight and isulated. MBC have suggested 200mm spacing for the pipe, and I've asked for a counter-flow arrangement.

 

Any suggestions would be really appreciated.

 

Thanks,

dj

[Jeremy Harris]

Insulation won't help, I'm afraid, as the temperature will just equalise both sides of it, as the heat loss through the kitchen units will be pretty low.  Given that it's unlikely that your floor will get warmer than about 23 to 24 deg C, even in cold weather, I'd not be overly worried about it.

 

200mm spacing for the pipe is fine, and works very well at the sort of very low heating requirement such a house needs.

 

Bear in mind that the floor will get a lot hotter in summer sun than it ever will from the UFH in winter!

[divorcingjack]

Thanks for your reply, that's a bit annoying that the insulation idea isn't a goer. All these worries about UFH not working under carpet ect, and I can't stop mine heating up! I'm more worried about the bin and the dishwasher than anything. I think we'll prob keep dishes etc in the island drawers, so not too worried about food spoilage.

 

We need a field experiment! Someone put their bin on a heating pad at 24 degrees and report back!

 

Cheers, dj

 

 

[Jeremy Harris]

It really isn't going to heat up, though.  UFH in a house like this doesn't even get the floor warm enough to feel as if it's heated when you're walking around in bare feet on it.  The highest surface temperature I've seen is around 23 deg C, so only a couple of degrees warmer than the room, and not enough to worry about.  Many houses will get to over 23 deg C in summer, anyway.  The dishwasher will get massively hotter than this when it's running, and will heat the floor a lot, rather than the other way around.

Edited April 4, 2017 by JSHarris

[bassanclan]

why don't you put one loop in areas which definitely need heat in either layout, one loop which needs heat in layout a) your idea and one loop in layout b) your architects idea?

Probably more loops than you had planned, but would give you that flexibility

[Jeremy Harris]

Because the UFH pipes are deep in the slab, the heat will tend to just spread until the whole slab is very close to the same temperature, whether there are pipes there or not.  I've found that the floor area under our stairs (which has no UFH pipes) is the close to the same surface temperature as the adjacent hall that does have pipes in.  In the kitchen, the boiler for the boiling water tap tends to make the under-plinth area very slightly warmer than the room, and we have bins in the unit next to the sink, so I expect that they will be sitting at around 24 to 25 deg C, not from the UFH, but from the small amount of waste heat coming from the boiler and waste pipe.

[Temp]

Insulation will increase the temperature of the UFH pipe and screed and reduce the temperature in the island units. I suppose there might be a small risk that the screed and tiles will crack due to differing rate of expansion?

 

We omitted the UFH under our island and had no issues with the screed and tiles there.

 

With bare feet we can definitely tell where the UFH was omitted at an internal doorway so I'm not so sure the heat spreading effect always occurs.

[Jeremy Harris]

19 minutes ago, Temp said:

Insulation will increase the temperature of the UFH pipe and screed and reduce the temperature in the island units. I suppose there might be a small risk that the screed and tiles will crack due to differing rate of expansion?

 

We omitted the UFH under our island and had no issues with the screed and tiles there.

 

With bare feet we can definitely tell where the UFH was omitted at an internal doorway so I'm not so sure the heat spreading effect always occurs.

 

This depends on the temperature differential and the amount of heat the UFH is delivering. 

 

This house is like mine, same builder, same sort of heating requirement per m².  There's one place on the floor surface where I can spot with a thermal camera or IR thermometer that the temperature is around 1/2 to 1 deg C warmer when the heating is on, and that's in the doorway to the utility room, where all the UFH pipes run through to the rest of the house.  You can't tell by walking on the floor in bare feet that this area is any warmer at all.

 

There is a significant difference between an UFH heating system like this that is delivering around 5 to 10 W/m² and a typical UFH heating system that may be delivering 50 W/m² or more.

[Nickfromwales]

@divorcingjack

I think your panicking over a quite insignificant item here. For starters, the cupboards / units have kick space so are immediately isolated from the floor, ( by the legs of the unit ), so the only 'worry' is over the bin.

My bin, out of circumstance, is next to the kitchen rad, literally 70mm away from it. As I bought a good quality Curver bin with a good swing lid I don't ever smell any guffs from it unless the kids have wedged something in there and the lid won't shut. 

Bearing in mind that food waste is separated now ( at least in Wales ) so what exactly is going to stink? 

Relax, and move on to worrying about how expensive a floor tile your missus will take a shine to  

[Declan52]

Maybe it's just me but if the bin starts to smell i empty it. And like nick all our food waste goes into a brown bin outside for composting by the council so very rarely smells.

[divorcingjack]

Thanks for all the responses, I think we are going to just put UFH in the lot for simplicity. I realised of course, that we are going to have a waste disposal unit in the island sink, so probably only recyclables in the actual bin. The floor finish will be powerfloated concrete, so no expensive tiles to worry about. I'm sure the husband will find something else to spend the cash on though @Nickfromwales.

 

@JSHarris, very useful to have a real-life comparison of a similar system, so thank you. Can I ask, is your floor comfortable to walk on in bare feet or does it feel cool? 

 

@bassanclan - just about at the same time you posted that, we had the same idea and were very chuffed with our problem solving! Great minds.

 

[Nickfromwales]

7 minutes ago, divorcingjack said:

I'm sure the husband will find something else to spend the cash on though @Nickfromwales.

I only open my mouth to change feet

[Jeremy Harris]

28 minutes ago, divorcingjack said:

@JSHarris, very useful to have a real-life comparison of a similar system, so thank you. Can I ask, is your floor comfortable to walk on in bare feet or does it feel cool? 

 

 

My other half walks around in bare feet, as did my brother's partner last weekend, and both say that the travertine stone we have laid directly on to the slab feels fine.  Our heating hasn't been on at all for at least a week, and I've just pointed the IR thermometer at a bit of floor on the North side (that gets no sun) and the surface is at 21.7 deg C.  The room temperature at the moment is 21.8 deg C, so pretty close to the floor temperature.

[jack]

1 hour ago, divorcingjack said:

 

@JSHarris, very useful to have a real-life comparison of a similar system, so thank you. Can I ask, is your floor comfortable to walk on in bare feet or does it feel cool? 

 

We have an MBC slab with a ~65mm polished concrete overlay.  I too tend to walk around barefoot all year round and find it perfectly pleasant.  My wife prefers warmer feet so tends to wear socks except when it's really warm, but she'd do that with any floor covering other than carpet I'd say!

 

Some will remember that we had an accidental puncturing of the UFH heating circuit in our study.  I've just gone through the entire winter with that UFH circuit turned off.  I wasn't able to measure the floor temperature, unfortunately, but it was markedly colder than that of the rest of the house, especially by Jan/Feb.  Even so, as long as I had any form of shoes or socks on, it was fine, and the room itself never felt hugely colder than the rest of the house despite the absence of any heating whatsoever.

 

 

@divorcingjack, if you're planning to polish an MBC slab, have you been following @MikeSharp01's threads about this? His latest one is here.

 

[SteamyTea]

7 hours ago, JSHarris said:

My other half walks around in bare feet, as did my brother's partner last weekend

Proper Cornish then me hansom

[divorcingjack]

@Nickfromwales Me too, very often

 

@JSHarris, very reassuring, thank you. Sounds very reasonable. We've moved from a very old stone cottage with slate floors, so this should be a nice change  to hopping about in the morning trying to find slippers. 

 

@jack - I remember reading about your UFH puncture. I assume there was nothing that could be done, once you discovered the leak? I will have a look at Mike's threads now, I must say, MBC are not keen to do it at all, but we have a contractor who's business  is polishing farm shed floors and MBC have agreed to let him take over the power floating of the slab once they have finished to the level they normally do. We've seen his work and it really is great. We're not looking for a highly polished surface, we like the imperfect industrial look. 

 

 

 

Edited April 8, 2017 by divorcingjack

[divorcingjack]

Actually, I just had one more question - based on the advice on this thread, I had decided to put UFH under both islands so as to have coverage whatever the layout turned out to be. We confirmed with the kitchen guy that he wouldn't need to nail anything into the floor and/or could use glue if necessary, but MBC have pointed out another issue that concerns them. 

 

Obviously, as the concrete cures and dries, quite an amount of moisture will come off it - they are worried that this could damage the kitchen units. Am I correct in thinking that we probably won't be fitting the kitchen for 5-6 months after the pour, by which time most of the moisture should be out, and leaving off the kick boards should allow air to circulate sufficiently. I had also thought of a small fan pointing under the island. 

 

Thoughts? 

[Jeremy Harris]

Pretty much all of the moisture in the slab will be incorporated into the curing concrete after about 4 to 6 weeks, so fitting the kitchen 5 to 6 months later will be fine.  I fitted our kitchen around 5 months after the slab was poured, and by then the slab was bone dry.

[divorcingjack]

That's what I thought tbh, Good to get a second opinion though, cheers. 

[bassanclan]

employ the old "1 day per mm" rule of thumb

 

[Nickfromwales]

3 hours ago, bassanclan said:

employ the old "1 day per mm" rule of thumb

 

Deffo good enough for concrete, and I allow a day per 2mm for dry screed. 

See the customers moan when they have to wait for the tiles to go down. ?

Got to go behind Everest and re lay one of their conservatory floors, ( laid in haste over liquid screed ), and not one single tile has stayed stuck down.