Underfloor heating over existing floor

[h-magic]

Have a look at Variotherm.
I’ve laid just under 100sq/m in there with tiles on top, in a caravan and it’s been totally fine so far and much improvement in heat output.
No cracks which I was dreading but the tiler said because of the screed they supplied was flexible it would be fine which it has been so far and only a build up of 18mm.

https://underfloorheating1.co.uk/ca...ting/premium-plus-variotherm-low-profile-kits

 

[deema]

I’m intrigued by the suggestion of needing a larger boiler. Naïvely I assumed that since the boiler was (big assumption I know)matched to the radiators, and the heat loss from each room remains the same the total heat required would remain the same??.

This is for my new house that we’ve just purchased. It has about 600mm of insulation in the roof, cavity wall insulation and triple glazing. I have another thread on trying to understand the plumbing of the system.

The house has about half of the downstairs as underfloor.

We are trying to make the house suitable for the years to come including working out how to get upstairs when we can’t manage steps anymore / accommodate my ageing parents needs. So, we hope that once done apart from pipe failures / blockages etc we should not need to go under the floors again

I’m about to refurbish all of the bathrooms so, putting in UFH before tiling makes sense if I’m going to do it. I like the idea of making the house ready for lower heating water temperatures ready for air source or other heating system to future proof the house. It’s presently heated by LPG…..a while unpleasant learning curve from oil, just to say getting gas is far from easy and the underground gas tank is about to run dry! Thank goodness it’s spring.

 

[Spectric]

I’m intrigued by the suggestion of needing a larger boiler.

Have you done the calcs, the UFH uses lower temperature water than the radiators. The UFH loops are not connected like a radiator where they have constant flow when there is a demand, instead they are fed via a mixer valve to " top up the heat " and the water is circulated round the UFH loops and hence the need for that extra pump.

 

[Pedronicus]

It’s presently heated by LPG…..a while unpleasant learning curve from oil, just to say getting gas is far from easy and the underground gas tank is about to run dry! Thank goodness it’s spring.

Slightly off-topic but I'm intrigued by your comment*. We are in the process of buying a house fuelled by LPG and the current supplier tops up when required as the gas levels are monitored remotely. They also own the bulk tank and carry out the required 10 year testing and 30 year replacement. Might be worth you researching the issues and regulations regarding bulk LPG tank installations which are far stricter than oil. Do you actually own the tank?

*I assume that you are hoping to shop around for best price LPG as one can with oil. Is that actually possible with LPG?

 

[Bingy man]

My time with b gas no pipe work buried in concrete or similar was covered under any of their various maintenance contracts, the same applied to under floor heating. I’m old school and believe most pipe work should be accessible ( I say most as obviously drainage pipes are difficult to access at the best of times) but in looking into ufh there are no joints under the floor for obvious reasons so I guess it comes down to how long will that plastic pipe work last underground, and what guarantees do the manufacturers give you and do insurance companies take the b gas aproach and don’t actually cover it for leaks .

 

[ian33a]

The pipework in our system is supposed to last for more than 50 years. It's about twenty in so far and will probably outlast our tenure. As far as I am aware, each circuit is a continuous loop with no joins, the manifolds being in the centre of the house. I believe that each pipe run can be up to 100m in length and this is why some rooms have two circuits supply them.

I'm not aware of a need for a larger boiler with UFH - but I didn't specify or install the system, so cannot be sure.

I was a bit nervous about moving from a house with radiators fired by a gas boiler to an oil fired boiler, thermal store and UFH. To be honest, in the short time that we had to view the property, it wasn't that clear to me what the system was and the agent certainly had no idea. That said, almost a year in and having understood the system and how best to run it, it's pretty decent in everything but extremely cold weather. The heating bills are frightening but I suspect that they would be even higher with radiators - it seems like the boiler isn't running madly trying to keep the place heated and most rooms feel comfortable rather than oppressively hot or chillingly cold (we run at about 18/19 degrees C 24/7 {with a modest set back at night} ). At least oil is starting to come down in price now.

 

[Spectric]

I believe that each pipe run can be up to 100m in length and this is why some rooms have two circuits supply them.

This is the important design aspect of UFH, you have pipe diameter, pipe spacing, pipe loop length, number of loops and layout pattern.

If you think of each loop as a temperature gradient starting from supply to the return then to ensure an even floor temperature requires careful thought, all layouts and designs will have some element of compromise. The two main layouts are a snail pattern or a serpentine patern where in the first the pipes run in a spiral towards the middle of a room and the later run up and down a room but it all depends on room sizes and room layouts.

 

[DRC]

I’m considering having underfloor heating added to my upstairs. The floor is wooden, and I’d dismissed it as I thought it involved taking the floor up adding insulation into the void, adding metal reflectors laying pipe and the floor back down. However, it’s been suggested that pipes can by layer on top of the floor and a thin screed spoiled, around 16mm total thickness added to the floor height. Does anyone know anything about this type of system, any good? Things to watch out for reasons not to do it? Best system?
Thanks

An alternative I have used on wooden floors is electric tape heating worked well underneath ceramic tiles in the bathroom & a wetroom.

 

[deema]

Slightly off-topic but I'm intrigued by your comment*. We are in the process of buying a house fuelled by LPG and the current supplier tops up when required as the gas levels are monitored remotely. They also own the bulk tank and carry out the required 10 year testing and 30 year replacement. Might be worth you researching the issues and regulations regarding bulk LPG tank installations which are far stricter than oil. Do you actually own the tank?

*I assume that you are hoping to shop around for best price LPG as one can with oil. Is that actually possible with LPG?

You are tied in for 2 years with a supplier so yes I need to shop around initially…….But they are saying it can take 3 months to transfer to a new supplier!!! I am therefore bottom of the pile with the supplier who had it under the last owner as I don’t want a contract just an interim top up.
I wouldn’t chose LPG based on my experience so far with supply. Oil was a doddle and twice the calorific value per ltr.

 

[XTiffy]

deema,
Back to your original post, I used NuHeat's LoPro upstairs and was completely happy with it. Having now had another look at NuHeats website, things have moved on a little. We used the poly sheets with the metal heat deflectors, the pipework was around 12mm in dia.and then 6mm ply wood sheeting before carpeting We zoned each bedroom (2), bathroom and landing. Manifolds were in a cabinet in the bathroom. From the website they now seem to use a self leveling screed. The underlay and carpet was rated for under floor heating. I paid for my employee to attend a training course at NuHeat and we installed all of the underfloor heating ourselves. Hope this helps!

 

[Speaker]

I’m considering having underfloor heating added to my upstairs. The floor is wooden, and I’d dismissed it as I thought it involved taking the floor up adding insulation into the void, adding metal reflectors laying pipe and the floor back down. However, it’s been suggested that pipes can by layer on top of the floor and a thin screed spoiled, around 16mm total thickness added to the floor height. Does anyone know anything about this type of system, any good? Things to watch out for reasons not to do it? Best system?
Thanks

@deema
if you lay anything on top of your existing floor don’t forget that you will need to raise the height of the lintels on every doorway - I know because I had UF heating installed and panicked part way through the install when I realised the doors wouldn’t fit due to the height taken by the system. Fortunately, I had enough room to be able to raise the lintels!

 

[Agent_zed]

I retrofitted water UFH heating throughout my house. I have pine tongue and groove floorboards and I didn't want to take them up as I sanded and stained them. I had to redo the plasterboard ceilings anyway so everything was fitted from below. I cross battened so I didn't have to cut into any of the joisted and dropped the ends of the loops down under each one. It was hard work pushing the pipes up and then using the ally spreader plates to hold them up. But it worked and has been there for ~6 years.

Downstairs was lucky as i could get under the floor for the living room and hall and again did it from beneath. Dining room I had to redo the floor anyway so did it from the top but instead of spreader plates placed the pipes on celotex and covered with gravel/cement mix.

Keep my house at ~18c which is perfectly fine. It's different to radiators as you get warm feet so you don't have to heat the room so much.

One problem with UFH though is ensuring there are cold places for storing things. Luckily i didn't do the alcoves by the firebreast so I have somewhere to put my guitars as you don't want to have them being constantly heated. Same with food etc you can't hide a chocolate bar in a bottom drawer that is directly on a heated floor. I've left some on the joist runs cold where wardrobes go etc .