So what’s it like?

We’re mid extension build and I’m starting to think about heating it, primarily the downstairs bathroom and hallway.

The slab is built to modern standards, so we’ll insulated with 150mm of kingspan beneath the concrete.

We don’t have mains gas or oil, so it’s all electric anyway and as it stands the rest of the house is on economy7

It’s great. Based on the the fact you have no gas or oil, it sounds like your best option. Be sure that if you’re fitting it under tile, you follow the manufacturers instructions to the letter.

We’ve got wet underfloor heating downstairs. It gives a lovely even temperature to the rooms.

Not having radiators helps with furniture placement too.

If we had the money I’d do upstairs.

Just to add confusion. ..I to have no gas or oil,but have a wet underfloor system heated by a back boiler on the wood burner.
Love it, but I do get cheap/free wood.

Mine is superb. Fitted by velta in Huddersfield which were recently bought out by upanor. Mine is the entire ground floor. Under York stone flags in kitchen/orangery. Carpet in living room. It’s set out into four zones so you can play about with the comfort settings. Underlay for the carpet is a specific one to underfloor heating. A certain tog rating, I can’t remember precisely which one. Works very efficiently, and only require mine to be set at 19 degrees.
You do need to remove a lot of floor substrate to get the depth for insulation, and screed plus your final floor finish.
Obviously York stone flags are very thick so take that into consideration if that’s an option.

Sorry. I never read that you don’t have. Gas. Sorry. One is the wet u floor heating. Never mind

I’ll sneak into your house and nap on your floor.
Something to consider.

I’m not going to rubbish it, because it might be fine for your application and the builders of my place may have not done the proper maths. However, I’ve found it to be not adequate as only source heating, in my home anyway. Your feet are constantly warm, which is very nice, but that’s about it, I’ve sometimes resorted to laying on the floor to get warm. The other thing is that rads are just instant, so you turn them on about 20mins beforehand and turn them off when finished, simple. Underfloor, you have to have it on more than an hour beforehand to get any benefit and then the floor retains heat for hours afterwards, like when you’re out or in bed (but never enough to heat the room), so there’s more planning involved, which with my chaotic work rotas is just not practical. I can’t wait to get back into a house with adequate heating and radiators.

The other thing is, how am I supposed to dry towels after showering, throw them on the floor?

I probably should point out that my main room has 4 massive windows without curtains, which probably doesn’t help.

We’ve electric underfloor in our conservatory, when it kicks in you can hear the electricity meter mutter “Jesus Christ” . For that reason other than the frost protection setting it only gets switched on over Xmas.

We also have electric underfloor heating in our kitchen and conservatory and I can concur with Ming. ^. I asked about trying to get a water heated underfloor heating system for the kitchen connected to our rads system but was told it wasn’t possible.

Works well with a wet system and insulated walls/floor/roof, not sure about electric but may work in smaller rooms such as a shower room.
BAN if you have a wet system off gas worth experimenting with times, one hour before does not sound like enough to warm up screed as ours works like a heat sink, also worth leaving on low but for longer periods, maybe even try overnight. Partly depends on how efficient your heat source is and if it works on a modular level (so can be turned low efficiently).
Anyhow I like ours in an insulated extension, the old house has radiators as it bleeds energy! It is a different way of heating and will take some getting used to as not instant.

I come from the insulate the crap out of the house to minimise the need for heating, and if you have a conservatory, you deserve everything you get. 😛
But my main question with underfloor heating is what happens when it goes wrong?

Wet system connected to rads doesn’t work. For starters the water temp is too high and underfloor heating efficiency comes from the thermal lag of heating up the floor, so having it come on and off twice daily won’t work. Electric is too expensive to run. Ok in a small bathroom/en suite but for the floor of a big room in a house it would cost a fortune, and forget it in a conservatory.

What happens when it goes wrong? What’s to go wrong? You don’t generally worry about pipes running in walls and other inaccessible places. There is even less to go wrong with underfloor heating as pipes are one continuous run with no joints underfloor, and usually there is less risk from you puncturing a hole in there as you won’t have the need to be drilling holes in your floor.

If you have the opportunity to install the it then do it. It’s cheap to install, even if you run the pipes and worry about connecting them further down the line,

Hi yes wet system on a gas boiler. I’m kind of aware that I’m probably using it wrong, but I can’t stop myself from using it like a rad system. if it has to be on when I’m out in order to maintain a temp, then there’s something fundamentally wrong with that in my mind.

I’m like others here, all I see is the boiler constantly working at ramming speed

What happens when it goes wrong? What’s to go wrong? You don’t generally worry about pipes running in walls and other inaccessible places. There is even less to go wrong with underfloor heating as pipes are one continuous run with no joints underfloor, and usually there is less risk from you puncturing a hole in there as you won’t have the need to be drilling holes in your floor.

It must come with some pretty healthy guarantees then. Cool.

We have ours set to 18° through night and 20° for the day time (wife’s home with the little one). Once up to temp the floor holds the heat so needs very boiler action to keep a constant temperature.

I fitted electric UFH in my last house, in the hallway and downstairs loo. Underneath travertine tiles.

It was lush. Every visitor loved it.

And we didn’t notice much of an increase in leccy bills.

Might be a different story heating a full house, but in that area it was perfect.

The controller is set to the time you want the room warm, the system then works out the current temp and the time to heat up the room and switches on in time to hit the temp at the desired time.

Wet system connected to rads doesn’t work. For starters the water temp is too high and underfloor heating

It’s perfectly OK to combine rads and UFH on the same system. The UF, if installed correctly, will have a separate manifold, pump, controls and blending valve. The temperature of the water in the rads will obviously be higher than that in the UF system.
However, if you read the OP’s question. You will see that his slab is already in place. liquid UFH is not an option for him. Unless he wants to dig it all up?

Woulnt have to dig it up. Could always go with something like uponor minitec so build hieght would be kept around 20mm. Benefits from faster heat up time as there is less mass to heat more like a traditional rads system with heat up times.

Lots of companies do an overlay system with minimum build up.

You could consider a thermal store type arrangement heated up on economy 7 overnight if you wanted a wet system. Or an electric boiler on maybe economy 10 tariff. I would think that an electric system would be very expensive to run, although you could use economy 10 and only have it come on at those times and use the floor as a heat store. Downside to that is you need to know if you are going to need the heating the next day as you will warm the slab up overnight.

We had it installed in an extension that we built. It’s lovely, a really nice even heat throughout the rooms. Under the screed and above 150mm of kingspan. It takes about 3 hours to heat up but holds the temperature for aaaaages.

Had it fitted at the same time as we had solar PV fitted, so can’t really comment on the cost of running it. I set the on/off times biased to daylight so that any electricity being generated is channelled into the floor.

The controller is supposed to ‘learn’ how quickly the room heats up, so you can set it to be at a certain temperature by a certain time, but it can’t really take account of the variability of the British weather.

Edit: It has gone wrong however – a cable fault means that the last 2 foot of one of the rooms doesn’t work. The rest works, so it’s not a massive issue, but rectification work will involve digging into the screed. It’s quite easy to find the fault (the cut-off between warm floor and cold floor is quite marked) so I think it could be quite a surgical repair and having a tiled floor means that the finish shouldn’t be too bad.

Hi yes wet system on a gas boiler. I’m kind of aware that I’m probably using it wrong, but I can’t stop myself from using it like a rad system.

You have read the manual right ?

Bit like buying a petrol car and filling it with diesel then wondering why it dont work and then having a good old moan about it.

In the right house with the right construction and a correctly designed system it can be good. I’m my insulated but drafty 1950s brick built with suspended concrete floor -not so much

To second what’s already been said –

Wet underfloor, in slab, is brilliant in a well insulated house but is not a sensible way to heat a poorly insulated house that’s only occupied at breakfast and evenings. Trying to use it like radiators is doomed to failure – you’re going to be trying to heat it up quickly and then get it hot so that it heats the room quickly.

Ours runs constantly but at a temperature only just above room temp (the flow temperature at the moment to the concrete floors is only 24C with the room sitting at a comfortable 20C). On the upper floors under wood it runs a bit hotter – the tiled bathroom floors feel warm when it’s below about 2C outside).