I know UFH gets discussed on here regularly so hoping some of you will have an idea of installation costs.

Property in question is a 60s bungalow which needs total renovation so existing system all coming out.
It’s a large 4 bed just under 150sqm.
Currently no insulation under floor.
Will have to be oil fired as gas not an option.

What sort of total cost am I looking at?

Bump for the lunchtime crowd, and an additional question: how much room height am I likely to lose by installing this?

Contact some companies and get some quotes?

What floor construction? Solid or timber suspended?

That will take days to come through, and i don’t have time to talk to multiple companies today. Expect I can get a good idea from here by the end of the day.

What floor construction? Solid or timber suspended?

Solid floor

60’s bungalow, no underfloor insulation, I’d not recommend UFH for this circumstance.

You have a maximum output of 100 W/m2 of net floor area I’d doubt you manage to hit the required room temperature as the heat losses will be greater than the possible heat input.

Existing uninsulated solid floors, you digging them up or laying insulation and screed on top??? typical floor construction is 75mm insulation 75mm screed to 150mm.

UFH is also very slow to react to change in temp, takes at least a day to heat up from cold, needs to be pretty much ‘always on’ (although at a lower set back temp over night). I’m finding it the most expensive heating bills I’ve had (and that’s in a recently modernised cottage with decent insulation levels fed from biomass boiler).

I’d be looking at an alternative heating type personally.

I don’t have domestic costs (I only have spec’d commercial systems > 450m2 floor area). Major cost will be whatever you do with your floor…

We have it in our kitchen extention and part off the original house and really pleased with it.100mm of celotex insulation,100mm of screed with special foam around the edges.
Our plumber arranged for a specialist company to work out what we needed and him a myself installed it.
You do need a good sparky to wire everything in and need to check that your boiler is powerful enough for the system.
It comes on at 6 am and usually cuts out around midday. When we come down in the morning the temp is normally around 18 degrees.
Best thing about it is coming back from a freezing ride at midnight and the floor is still warm.

Will have to be oil fired as gas not an option.

We’re just putting water-based underfloor heating into the granny annex been built for my folks, next door to us.

No gas here but it’s costed around an electric boiler – mainly due to the oil price 3 years ago, but also as it made it far easier on construction than trying to run an oil feed from our oil tank, and the electric boiler needed is tiny.

Floor-wise, it’s starting from (almost) scratch with it been a conversion of old farm buildings with dirt floors. So for you I guess you’d need to either dig out the old or raise the floor.

Ive just finished extending our house, doubling the footprint up to 110m/2. I took out the old timber suspended floors & replaced with new concrete slabs with 100mm celotex over, then a liquid screed with UFH pipework within.

I used Wunda heating to supply all of the kit. You can provide them a drawing and for a small charge (think it was £50) they design the layout for you.

The entire kit cost about £1100 for a 6 pipe system. I fitted it all myself, and my electrician wired it in with a new Nest thermostat.

Everything seems to be working well, and the heat levels in the house are spot on. the difference between the heat on the inwards loop is only about 7-10 degrees lower than the flow, so the boilers not having to put much effort in either.

Thanks for the replies.

Hmm…
I had not expected it to be anywhere near as much as 150-200mm additional floor height.
That could be the deal breaker.
A major excavation project like that would definitely not be worth the hassle/expense.

Shame as I really really wanted to avoid radiators…

The entire kit cost about £1100 for a 6 pipe system

Wow – that seems much cheaper than I was expecting.

Ours cost £950 for a 4 pipe system plus cost of sparky and additional pipes from boiler to manifold.

Thinking about this, I may end up excavating the existing floors anyway.
I will want to add insulation to the floor regardless of the heating system, and I’m not sure I would want to lose even 75mm of height – the associated hassle that would cause would probably make me wish I had just bit the bullet and done the full job from the start.

Have y0u done any research into this at all ? You can get lo-profile systems installed. Would it be something you’d do yourself or get a firm in from start to finish ?
http://www.thefloorheatingwarehouse.co.uk/acatalog/Low-Profile-Underfloor—-150mm-Spacing.html

I recently tiled a wet underfloor system, that was only 15mm thick. I can’t remember the brand but it was aluminium formers on insulated ‘pallets’ which then had the pipes clipped into it. you can then prime and tile direct without screeding over. The words ‘expensive’ were used however.

I’ve been looking for a retrofit wet system.Overlay lite15 looks promising as a low profile system
polypipe

When I did ours, I couldn’t get a straight answer from the manufacturers (JG Speedfit) whether you can tile directly onto the overlay system. So I used Knauf brio non-insulating backer boards on top of the overlay UFH, then tiled on those. A small part of another level I couldn’t use the backer boards, tiled onto the overlay UFH boards. Those tiles are starting to come loose.

The lowest price systems I found were from wundafloor. They were good to deal with and I’ve no issues with the quality of what was supplied.

They sell a number of different overlay systems as well as in screed. Overlay systems (Ie not pipes in screed) are much quicker to react than in-screed so behave much more like radiators so are better suited to a less insulated house where you run the heating only for a few hours a day. (In screed underfloor is slow to react and works better at a low temperature run constantly in a well insulated house)

If you’re running them under tiles you can run it at a higher temperature as well. The lower the profile, the thinner the pipe, the lower the output so be careful with the low height stuff.

Thanks for the replies all – very helpful.

The low profile overfloor stuff looks like the solution if I decide not to dig up the existing floors.
I guess the question is how efficient is it when used on top of an uninsulated concrete floor block. I suppose that some of the heat gets lost into the ground underneath the block… but I can’t imagine it’s that much as it would have to travel through the block first, and the path of least resistance is surely into the room above so most of it’s going to go that way I would think.
I have no idea what I am talking about really though – might be time to talk to some of these companies.

I guess the question is how efficient is it when used on top of an uninsulated concrete floor block. I suppose that some of the heat gets lost into the ground underneath the block… but I can’t imagine it’s that much as it would have to travel through the block first, and the path of least resistance is surely into the room above so most of it’s going to go that way I would think

I’m far from expert in thermodynamics (and a little knowledge can sometimes be a dangerous thing) but I think you’ve a few important misconceptions there.

Don’t confuse ‘hot air rises’ with ‘heat rises’ – if you put a pipe of hot water in a solid it will conduct heat equally in all directions. With no insulation below to slow the transfer of heat in that direction you’re basically trying to heat the ground. I’m pretty sure that with an uninsulated slab you’d be better off using radiators to heat the air in room.

We had wet system put into our extension. 44m2, 45mm pumped screed (was to be 60mm but drying times were too long). All up 5k. We have concrete, 120mm celotex, membrane, pipework and screed, then tiles on top. The build is so well insulated we’re still running the UFH at ~28c on the TRV.

With no insulation below to slow the transfer of heat in that direction you’re basically trying to heat the ground. I’m pretty sure that with an uninsulated slab you’d be better off using radiators to heat the air in room.

I will put some more research into this, but I fear you might be right…

The ‘thin’ system I had to tile was insulated pallets with an aluminium former for the pipes so was insulated to some extent, I guess the alu formers acted like a heat sink too. We had to use a special primer that etched the aluminium before tiling. The pallets were just stuck down with std flexible floor tile adhesive.

Much garden? Wet underfloor works well with ground source heat pumps. Insulation is key to minmising your losses with any kind of system of course.

I was quoted 4600 (inc vat) from lo pro 15 floor for 65 sqm. They also said that about 10% of the heat goes down into the uninsulated floor as opposed up into the room.

Thanks for the info all.

Much garden? Wet underfloor works well with ground source heat pumps.

No, not a lot. I’d expect this requires quite a bit of land doesn’t it?

They also said that about 10% of the heat goes down into the uninsulated floor as opposed up into the room.

That doesn’t sound too bad. And surely any insulation at all would help – might be able to do 30-50mm of insulation underneath a 20mm low profile system if I’m lucky.

Price up getting the floor dug out – it’ll only be this easy once. Insulation is cheap, fuel will only ever get more expensive. The savings will keep on coming year after year if you do it properly now.

Price up getting the floor dug out – it’ll only be this easy once

This is true. Definitely going to get quotes for all options.

We have ground source here (but have a massive garden and about 300m of pipe out there – it was a car park tho so we had to dig it up anyway!). Used NU-Heat and absolutely had to lay lots of insulation first. Ended up raising a couple of lintels. Did consider digging the floor out. Builder talked us out of it. Engineered oak floor on top. Not concreted the pipes in.

We love it but it was a heck of a faff. Still run radiators off the ground source upstairs (you need bigger ones) but much prefer the UFH downstairs.

We also looked at air-source but might need a few units for what you’re talking about and 9 years ago they were noisy/nowhere near as efficient. Might have changed.

They also said that about 10% of the heat goes down into the uninsulated floor as opposed up into the room.

I really would take that with a big pinch of salt without some proper test evidence to back it up. I reckon they’ve got that figure from

which is an estimate of where you lose heat in a completely uninsulated house to give you priorities for adding insulation.

Having insulated under the floor then 10% is a huge underestimate if you already have a well-insulated roof, cavity wall insulation and reasonable glazing/doors. I know heat rises but in a typical British house the roof will be R5, the walls R1.5 and the floors R 0.3. Underfloor heating over a layer of polyurethane insulation seems a good idea to me.

I know heat rises

No, once again. Hot *air* rises because it’s less dense and thus lighter. In a solid ‘heat’ will be distribute evenly in all directions. Sticking your heating into or onto an uninsulated slab you’ve got something much more complicated going on.

Having insulated under the floor then 10% is a huge underestimate if you already have a well-insulated roof, cavity wall insulation and reasonable glazing/doors.

I suspect you are right. Sounds like a number they just pulled out of thin air.

I’ve decided I’m not going to do it unless I can get some insulation of some sort in under the heating system.

I too was sceptical about the 10% figure. There is some form of foil underneath the pipes in the nu heat lo pro but can’t see how 90% would still go into the room.

Edit – just had a call coincidentally from the Nu heat guy. The lo pro uses 10mm pipes, raises the floor by 15mm and the pipes are laid into gypsum backing board. He also said again that approx 10% of the heat would be lost downwards.

The quote for 65 sqm was 3800 + vat.
The price for a traditional wet system, which would involve digging the floor and putting in insulation etc was 1800 + VAT.

He reckons running costs between the 2 systems would be similar, they work at the same heat, just one has more pipe work and is more responsive.

Edit – just had a call coincidentally from the Nu heat guy. The lo pro uses 10mm pipes, raises the floor by 15mm and the pipes are laid into gypsum backing board.

The gypsum board is a good idea for an overlay system – it’s heavy and adds some mass to the floor to spread the heat (ie it’s a *bit* like a thin layer of concrete). We’ve got a gypsum overlay system under our tiled bathroom floors

10mm pipes are very small and it’s hard to get a good flow through them which limits the heat output. Standard for in screed systems is 15mm pipe but the internal dimension of 10mm is a lot less than 2/3 of 15mm because the wall thickness doesn’t change so much.

He also said again that approx 10% of the heat would be lost downwards.

I’d really call bullshit on that. A salesman trying to make a sale. .

He reckons running costs between the 2 systems would be similar, they work at the same heat, just one has more pipe work and is more responsive.

I’d call bullshit on that as well. Ask them for a proper heat output calculation – they should be able to give some figures. Get some quotes from other suppliers and compare.

I’d say that the LoPro system they’re suggesting is fine for upper floors in a house but not suitable for putting on top of an uninsulated solid ground floor.

I’ve just had a quote from robbens. Seems well thought through, circa 5.5k for about 240sqm. Downstairs is about 2.5k of that and upstairs about 3k. They do some actaul heat loss calcs…

Doesn’t included taking up and relaying the floor though.. I reckon all told we should be under 10

I’d second David Robbens, although I do have some connection to them in that I’ve used their systems for nearly 20 years, but their systems work and unlike many others they do a decent design service.
I’ve had dealings with several underfloor companies and they do stand out as having a good product.