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Fareastdriver
29th Jan 2018, 21:52
I live in a listed building built in 1927. It has been converted into flats and I live in a part of it. The main rooms are twelve foot high with nine foot sash windows. To heat the lounge there is a large six foot double panel radiator which works fine but not nice to look at.

The radiators in the hall got in the way so I removed them and installed underfloor electric heating. This works fine and would cost a bomb to run all the time but the other rooms push out enough warm air to make it unnecessary apart from very cold weather. The bathroom and en-suite are also similarly equipped and very pleasant it is when one is showering/bathing.

What I want to do is install a water based underfloor heating using the existing boiler and pipework to the lounge and bedrooms.

The floor is 75mm. lathes and 18mm. flooring laid in the original concrete floor. The central heating pipework is easily accessed so I could install a floor thermostat in the wall to control a valve underneath the floor with the usual maintenance shut valves, etc.

The floor would be covered with insulated grooved base for the pipes with the usual horrendous routing. The floor would require three patterns as the heating area would be 5 metres/six. It would then be cover with wood/synthetic flooring.

I am more then capable of doing it by myself but I would like the opinions of any prooners who have installed wet underfloor heating to gauge a reaction.

Pontius Navigator
29th Jan 2018, 22:08
We are moving in to a new build with a wet system on both floors. From what I read, the pipe work is laid out on a series of ribs and seem to be gathered in a cupboard. It all works well, the only issue is where the pipes actually are.

I think VP959 said he backed plastic pipes with foil so a metal detector would work. Sound plan I think.

The other thing is the DIY/professional thread - time/money and satisfaction/warranty issue. As you are in a shared accommodation you also have an insurance issue aside from your grade 2 listing.

G-CPTN
29th Jan 2018, 22:10
Don't current building regulations demand a thick wad of polystyrene insulation?

yellowtriumph
29th Jan 2018, 23:15
We used to live in a house that had a wet underfloor heating system. I’d suggest a look at this site

Www.uponor.co.uk

They used to be called wirsbo, and they used to be the uk market leaders. They have some useful info on their which might give you some initial pointers.

Espada III
29th Jan 2018, 23:26
I live in a listed building built in 1927. It has been converted into flats and I live in a part of it. The main rooms are twelve foot high with nine foot sash windows. To heat the lounge there is a large six foot double panel radiator which works fine but not nice to look at.

The radiators in the hall got in the way so I removed them and installed underfloor electric heating. This works fine and would cost a bomb to run all the time but the other rooms push out enough warm air to make it unnecessary apart from very cold weather. The bathroom and en-suite are also similarly equipped and very pleasant it is when one is showering/bathing.

What I want to do is install a water based underfloor heating using the existing boiler and pipework to the lounge and bedrooms.

The floor is 75mm. lathes and 18mm. flooring laid in the original concrete floor. The central heating pipework is easily accessed so I could install a floor thermostat in the wall to control a valve underneath the floor with the usual maintenance shut valves, etc.

The floor would be covered with insulated grooved base for the pipes with the usual horrendous routing. The floor would require three patterns as the heating area would be 5 metres/six. It would then be cover with wood/synthetic flooring.

I am more then capable of doing it by myself but I would like the opinions of any proo5ners who have installed wet underfloor heating to gauge a reaction.

Central heating works at about 65C. Underfloor heating works at about 40/45C I think so you need to find a way of running both systems off the same boiler.

k3k3
29th Jan 2018, 23:28
I have had underfloor heating installed in a 1930 semi-detached house. I used a system from a firm called Nu-Heat in Devon and am more than happy with the results.

https://www.nu-heat.co.uk/resources/case-studies/lopromax-renovation/

charliegolf
30th Jan 2018, 05:30
Central heating works at about 65C. Underfloor heating works at about 40/45C I think so you need to find a way of running both systems off the same boiler.

The system k3k3 references will have all the bits to address that.

CG

n5296s
30th Jan 2018, 07:22
Can't comment on installing it, but our house has underfloor heating throughout, copper pipes embedded in the concrete foundation. I find it very pleasant. However the heat distribution throughout the house is very uneven - the kitchen where the pipes come from the boiler is at least 5 C warmer than the coldest room (my office, where I'm sitting now). Doesn't help that the house is basically a long corridor wrapped around a courtyard, so the pipes have a long way to go.

The big problem with this system is that the pipes do corrode, and leaks are a nightmare to trace and fix.

(The house is a very characteristic Californian design called an Eichler, if you're interested - lots about them, including the heating system woes, on the web).

tescoapp
30th Jan 2018, 07:22
You would be best doing the whole lot and get rid of the other wall radiators and then you could drop the feed temp down to 35 deg.

I would be temped to do the hall as well.

Then get one of these fancy control systems to learn your house and control it. Something like a Nest controller.

tescoapp
30th Jan 2018, 07:27
Can't comment on installing it, but our house has underfloor heating throughout, copper pipes embedded in the concrete foundation. I find it very pleasant. However the heat distribution throughout the house is very uneven - the kitchen where the pipes come from the boiler is at least 5 C warmer than the coldest room (my office, where I'm sitting now). Doesn't help that the house is basically a long corridor wrapped around a courtyard, so the pipes have a long way to go.

There should be a way in the manifold to balance that or you could go the smart way of the manifold having smart valves on them and a controller will open and close them to maintain the temperature at your desired point.

Balancing you just turn down the supply for the loop in the kitchen gradually until its the same temp as the furthest away room.

sitigeltfel
30th Jan 2018, 08:16
Ours is an oil fired, water system with underfloor heating on the ground floor and traditional water filled radiators on the upper floors. There are two Danfoss pumps, one for each floor, and a De Dietrich VM computer controlling it. The radiators have thermostatic valves while the underfloor portion has a room thermostat linked to a motorised valve. There is also an exterior temperature sensor linked to the computer.

In all it works well, the lounge tends to be a degree or two cooler than the other rooms but there is a woodburner for chilly nights. I am planning to have the system flushed and refilled once winter is over. There may be debris in the lounge pipes stopping it from flowing efficiently.

Leaks are not to difficult to trace, in a previous property I got a quote from a company to do that using a thermal imaging camera then remembered that the husband of one of my employees was a fireman. He brought round one of their cameras and within minutes we could see where water had leaked from a fracture. It showed up as a bloom around the leak.

Pontius Navigator
30th Jan 2018, 08:24
In contrast to n5269, ours is plastic pipe. It appears that the system has two primary branches, one on the ground floor and one upstairs. From these branches, pipes run to every living space. Each space has its own thermostat and timer function.

As our builder said, in contrast to a low volume, high temperature system, UFH is high volume low temperature. You start two hours before you need the heat and off two hours before you don't.

It gives a gentle warmth. Our hit air system also gave a gentle warmth but the UFH is not a fast response system. No good for workers with irregular hours or habits! Much better for old codgers like us.

UniFoxOs
30th Jan 2018, 08:54
Don't current building regulations demand a thick wad of polystyrene insulation?

I don't think one would need to apply the regs in the case of a change such as this, but there would be a significant loss of heat into the concrete floor and the ground (or flat) below.

I have just fitted plastic UFH pipes in the retirement bungalow and I took up the original concrete floors then dug out enough depth to allow a fresh concrete sub-base, topped with the required 75 mm of PIR insulation (plus another 100 of EPS below that) and finished with the pipes in a 70mm screed.

VP959
30th Jan 2018, 09:14
I designed and installed our underfloor heating. There are several things to consider, especially for a ground floor.

The first is heating efficiency. UFH in a ground floor is almost always less efficient than radiators, as heat will be lost down through the floor, unless a great deal of insulation is added underneath it. We have 300mm of EPS underneth ours, so only lose a few percent into the colder ground beneath, but it if you can only add, say, 100mm of insulation underneath then the losses will be higher. The reason is just because the ground will stay at a reasonably constant 8 deg C or so and the UFH pipes will run a fair bit warmer than room temperature, so there will be a constant heat loss path through to the ground that just increases the running cost.

The second point is related, because it sets the temperature that the UFH has to run at in order to provide enough heat for the room. If you already know how much heat you get from your radiators, in kW, and are happy with the heating level in winter, then you can work out how hot the floor surface needs to be to deliver the same amount of heat. This is non-linear, but the maximum that UFH can sensibly deliver is around 60 to 80 W per square metre of heated floor area, and ideally you should aim for a lower figure if you can, say no more than 50 W per square metre.

The floor surface temperature is determined by the flow temperature into the UFH, and adjusted by means of a thermostatic mixing valve, similar to the way thermostatic shower controls work. The lower the UFH flow temperature the better the efficiency (lower losses down to the ground beneath) but also the lower the heat output. The flow temperature will always be higher than the floor surface temperature, as there is always thermal resistance between the pipes and the floor surface (floor boards, underlay, carpet etc). Here are some sample floor surface temperatures and associated heat outputs in W/m, assuming that the target room temperature is 21 deg C:

24 deg C surface temp = 19.9 W/m
25 deg C surface temp = 41.0 W/m
26 deg C surface temp = 52.4 W/m
27 deg C surface temp = 64.0 W/m
28 deg C surface temp = 75.9 W/m

Generally, a floor surface warmer than about 28 deg C is a bit too warm, and the losses downwards will be pretty high at that sort of temperature unless you can put a lot of good insulation underneath it.

The evenness of the floor temperature depends partly on the system used and partly on the floor surface temperature required. Generally the starting point is 150mm between the pipes if setting them in screed or concrete, or using conductive aluminium spreader plates. This can be decreased to 100mm as an absolute minimum (but will be greater on the bends at the ends probably) for a higher floor surface temperature, or can be relaxed to 200mm if you find you don't need as high a floor temperature and have something like a screed or concrete system that tends to even the heat out.

We have our pipes set inside a 100mm thick concrete floor slab, tied to the steel reinforcing mesh, at 200mm centres. The concrete sits on 300 mm of EPS (expanded polystyrene foam) and in the very coldest weather (-10 deg C outside) the floor surface needs to be around 23.2 deg C to keep the whole house at about 21 deg C. The flow temperature into the UFH pipes on our system is between 25 and 28 deg C, and is mixed down from a tank of water that is heated to 40 deg C, but the mixer would work just as well if the tank was at a higher temperature.

The normal way to install these systems is to fit two manifolds, with as many outlets as you think you will need. As a rule of thumb, no single loop of UFH pipe should exceed 100m, and most houses will need several separate loops. You can zone the system by room, but because the response time will be a bit slower than radiators this may not work that well. We run our system with all the loops open all the time, and keep the whole floor at the same temperature, as it just works OK that way.

The manifolds are connected together by a circulating pump, that pumps water around the UFH. The flow manifold will have a thermostatic mixer valve, that blends hot incoming water with some of the cooler water coming back from the return manifold to set the floor surface temperature. The rest of the cool return flows back to the boiler, as with a radiator system.

Depending on the type of boiler you have, the heat output you need from the floor and the area of heated floor (and hence volume of water in the pipes) you may find you need a small buffer tank to prevent the boiler from short cycling. We have a 70 litre tank that's heated to 40 deg C as a buffer, and that works well for the 75m of heated floor we have.

Hope the above doesn't seem to complex, in reality the system is pretty straightforward and can be a DIY job with a bit of forethought.

yellowtriumph
30th Jan 2018, 09:16
Central heating works at about 65C. Underfloor heating works at about 40/45C I think so you need to find a way of running both systems off the same boiler.

Wet systems mix the returning cooler water with the outgoing hot outgoing water to get the right temperature through the pipes. This 'mixed' water then goes to a manifold where the individual pipes go out to their respective zones or rooms - reverse manifold procedure on the return side.

It's all likely to be under the control of a small microprocessor system etc. The microprocessor control will also take inputs from the individual room thermostats (consider radio stats) and control the on/off valves for each circuit, and the operation/overun of the boiler for example.

Getting the right pipe lengths and the pattern of laying it down under the floor is crucial to get and maintain sufficient and correct rooms temperature as is selecting the correct type of finished flooring.

The practical side of laying it is not difficult at all, but it's absolutely critical to get the 'maths' of it correct in the design stage. It's not a guessing game or finger in the air stuff or you may end up being disappointed.

Edit to say VP959 has added a lot more detail above - as I can now see!

Pontius Navigator
30th Jan 2018, 10:01
Noit mentioned so far is the planned floor covering. I don't know the pris and cons but suspect a tile surface will be the best surface for heat conduction with a wooden floor stuck to the base as the next. A laminate floor laid on a noise insulating sheet would be less effective. If you chose a carpet you need one with a tog rating , including underlay, of less than 2.5.

anchorhold
30th Jan 2018, 12:00
I think the building regulations only apply to new builds, but they are good to follow, if that is feasable.

I have never really seen the point, and thought it was a passing fad. It might be usefull if you are short of wall space.

The other issue is we really do not know what the life of the plastic pipes and seals are and how they react with Fernox.

Bull at a Gate
30th Jan 2018, 12:03
Wouldn’t it be easier to move to Australia?

Blacksheep
30th Jan 2018, 13:24
It isn't the building regulations you need to watch out for, it's the lease. Check the lease document to see what it says about alterations. Putting in water based underfloor heating could cause major damage to neighbouring flats in the event of a leak, so there's likely to be a prohibition.

occasional
30th Jan 2018, 14:52
We have got one of those sophisticated controllers, but have ended up with a program which says "Switch off at 10pm".

A fairly simple controller is probably quite adequate.

VP959
30th Jan 2018, 15:24
All we have is a simple programmer that sets the day and time that the heating comes on and off, plus a normal wall thermostat in the hall that controls the temperature. All very standard and simple.

The UFH is turned on and off by applying power to a motorised valve that that allows hot water to the thermostatic mixing valve and also applies power to the UFH circulating pump. I used a wireless thermostat, just to make it easier to install, and put the programmer on the wall in the utility room, where the UFH manifolds are fitted. I could have used a combined programmable thermostat to do the whole job with one unit if I'd wanted to.

Because of the relatively slow response time it's worth fitting a low hysteresis room thermostat, one that only has a small temperature difference between the turn on and turn off points. The unit I fitted runs with a +/-0.1 deg C hysteresis, that seems to work OK.

Fareastdriver
30th Jan 2018, 17:19
There seems to be an awful lot on concrete in everybody's floors. As I said my floors are 18mm. chipboard on 75mm lathes. The plastic pipes will sit in grooved insulation on top of the floor otherwise I will have to raise all the doors. They have a working pressure of 10 bars and up to 80 degrees C. The electric heating I put in the hall at 140 watts/sq. metre brings the hall, 15 m sq. from 17C to 24C in fifteen minutes and that has the same base as the lounge so I cannot see where it is losing a lot of heat to the concrete floor with a 75mm. air gap. As the wires get nearly too hot to touch I cannot see the problem of using the boiler at 70.C especially as it will lose temperature on the way there and certainly whilst it is whizzing around the floor.

The boiler has individual temperature controls for the heating and hot water and can be reduced down to 50.C for the central heating and the hot water is not affected so I cannot see the need for a separate tank or mixer.

I will be giving it a go in the summer. The radiator will stay in position on the wall until it's up and running before a couple of strong lads earn some beer money down at the scrappie.

VP959
30th Jan 2018, 18:35
If fitting to a suspended timber floor, then the normal way to do it is to fit insulation between the joists, then fit aluminium spreader plates that also act as the mounts for the pipe (makes it easy to lay the pipe and spreads the heat evenly across the top - so is more efficient) that look like this: Underfloor Spreader Plates (http://www.underfloorspreaderplates.co.uk/)

The water temp will need to be reduced, because you don't want the floor to get too hot. The wires should very, very definitely not get too hot to touch with electric UFH, they are only rated to a maximum operating temperature of around 35 deg C or so, IIRC, and if they are getting that hot then that indicates just how much heat is being wasted down through the air gap, as the floor shouldn't need to get above about 30 deg C as an absolute worst case. 124 W/m is an exceptionally high heat output, way, way over the normal range, and itself indicative of very poor overall heating efficiency.

The UFH heating pipes are 16mm OD and will only connect to a manifold, with O ring seals and clamps, plus you will need a pump to circulate water through the pipes, as the flow resistance will be a lot greated than with a radiator, plus you control the heat output evenness by adjusting the flow rate between the separate loops of pipe, to compensate for varying lengths (bearing in mind that 100m is the maximum length per loop). The pipe needs to be UFH pipe, with has an oxygen barrier (prevents oxygen getting in and causing corrosion elsewhere) and the normal stuff used is PEX-Al - PEX, which is a multilayer pipe that includes a sandwiched internal thin aluminium layer that makes the pipe a lot easier to lay (it bends easily and doesn't spring back).

Fareastdriver
30th Jan 2018, 19:47
I am aware of the spreader plates between joists but in my floor there are no joints, its just chipboard on lathes. It would be virtually impossible to lift the floor so that is out.

The vendors seem to think that insulation sheets with channels for the piping plus interlocking floor panels are the best that can be achieved. Heat rises and modern high density insulation is very effective plus the natural insulation of chipboard so I don't expect too much heat loss.


We shall see.

VP959
30th Jan 2018, 21:43
Don't believe the BS about insulation from installers. As mentioned earlier, UFH will always, without fail, lose heat downwards, it's simple physics - the UFH pipes lose heat in all directions and any heat that flows downwards is wasted as far as heating your rooms are concerned. The more insulation under the UFH the better, but the bare minimum is really 100mm of very good insulation material, like PIR foam, preferably more.

As I mentioned earlier, we have 300mm of eps foam underneath our UFH, run it at low temperatures, and yet still have to accept a few percent of waste heat going downwards, it's just a normal penalty for UFH, but the higher running cost is offset by the convenience of having free wall space and the added comfort of having warm floors.

If you let us know the thickness and type of insulation and the thickness and type of covering above the UFH I can easily do a quick calculation as to how much heat will be lost downwards.

G-CPTN
30th Jan 2018, 21:52
Open fire chimneys are pernicious and draw air under doors and around windows and conventional radiators generate 'thermals'.

How do draughts manifest themselves with UFH?

yellowtriumph
30th Jan 2018, 21:55
All we have is a simple programmer that sets the day and time that the heating comes on and off, plus a normal wall thermostat in the hall that controls the temperature. All very standard and simple.

The UFH is turned on and off by applying power to a motorised valve that that allows hot water to the thermostatic mixing valve and also applies power to the UFH circulating pump. I used a wireless thermostat, just to make it easier to install, and put the programmer on the wall in the utility room, where the UFH manifolds are fitted. I could have used a combined programmable thermostat to do the whole job with one unit if I'd wanted to.

Because of the relatively slow response time it's worth fitting a low hysteresis room thermostat, one that only has a small temperature difference between the turn on and turn off points. The unit I fitted runs with a +/-0.1 deg C hysteresis, that seems to work OK.

May I ask how you deal with boiler overrun? I’m thinking that when your system calls for heat them I imagine power is applied to the mixer valve (ours was a manual mixer valve but I gather yours may be controllable), to the circulation pump and to the boiler.

I assume yours is a multi loop system so all the above remains stable until the last loop signals it is up to temperature and heat is no longer required. Ours was a 4 loop system and each area with its own wireless room stat signalling back to a central control system. So, when the last loop is up to temperature 3 valves are already closed and as the last (4th) loop valve starts to close, the circulation pump and boiler continue for another 5 minutes so that the boiler is not left with a ‘bellyfull’ of hot water. The manifold valves take 5 minutes to close so you can see the link between the timings. Would be interested in your thoughts even though we no longer live in the UFH house.

VP959
30th Jan 2018, 22:12
May I ask how you deal with boiler overrun? Im thinking that when your system calls for heat them I imagine power is applied to the mixer valve (ours was a manual mixer valve but I gather yours may be controllable), to the circulation pump and to the boiler.

I assume yours is a multi loop system so all the above remains stable until the last loop signals it is up to temperature and heat is no longer required. Ours was a 4 loop system and each area with its own wireless room stat signalling back to a central control system. So, when the last loop is up to temperature 3 valves are already closed and as the last (4th) loop valve starts to close, the circulation pump and boiler continue for another 5 minutes so that the boiler is not left with a bellyfull of hot water. The manifold valves take 5 minutes to close so you can see the link between the timings. Would be interested in your thoughts even though we no longer live in the UFH house.

We don't have a boiler, just an inverter controlled air source heat pump, as we're off the gas grid, and the whole house only needs an absolute maximum heat input of about 1.6 kW to maintain 21 deg C indoors when it's -10 deg C outside. In practice, the heat pump rarely needs to deliver more than about 500 W in winter, so less than 200 W of electricity consumption.

We run the heat pump at 40 deg C into the buffer tank, and the UFH draws from that, via a thermostatic mixer valve, plus we use that to pre-heat the hot water, via a plate heat exchanger (rather like an instant water heater) and then boost that to about 50 deg C at the taps using a new bit of kit, a phase change material heat store, the Sunamp PV: https://www.sunamp.com/

This is usually charged up from a big (6.25 kWp) solar panel aray, but in the winter we have a boost system that can charge this from the mains for a couple of hours early in the morning.

Overall, this system works well, and we don't have any electricity bills, we still generate more electricity than we use, even with everything being electric and not getting the high feed in tariff subsidy that was being offered a few years ago (we get paid less for exporting electricity to the grid than we pay for importing electricity from the grid).

VP959
30th Jan 2018, 22:17
Open fire chimneys are pernicious and draw air under doors and around windows and conventional radiators generate 'thermals'.

How do draughts manifest themselves with UFH?

Our house is very airtight, with a mechanical ventilation and heat recovery system that extracts warm, damp or smelly air from some rooms, recovers the waste heat from it and uses that to warm up filtered fresh air that is fed back into all the main living rooms and bedrooms. This saves us around 70% of our heat loss if we didn't have it, and had to rely on window ventilators and extractor fans, and the big benefit for me is no hay fever, as the intake filter doesn't allow pollen to get into the house.

The result is we have no draughts at all, we get very clean and fresh air in the house (all the air in the house is changed roughly once every 2 hours) and the hidden benefit is that we have very little dust anywhere.

yellowtriumph
30th Jan 2018, 22:18
We don't have a boiler, just an inverter controlled air source heat pump, as we're off the gas grid, and the whole house only needs an absolute maximum heat input of about 1.6 kW to maintain 21 deg C indoors when it's -10 deg C outside. In practice, the heat pump rarely needs to deliver more than about 500 W in winter, so less than 200 W of electricity consumption.

We run the heat pump at 40 deg C into the buffer tank, and the UFH draws from that, via a thermostatic mixer valve, plus we use that to pre-heat the hot water, via a plate heat exchanger (rather like an instant water heater) and then boost that to about 50 deg C at the taps using a new bit of kit, a phase change material heat store, the Sunamp PV: https://www.sunamp.com/

This is usually charged up from a big (6.25 kWp) solar panel aray, but in the winter we have a boost system that can charge this from the mains for a couple of hours early in the morning.

Overall, this system works well, and we don't have any electricity bills, we still generate more electricity than we use, even with everything being electric and not getting the high feed in tariff subsidy that was being offered a few years ago (we get paid less for exporting electricity to the grid than we pay for importing electricity from the grid).

I see. I think you would agree yours is fairly unusual system albeit one that works very well in your circumstances. Thanks for the explanation.

Pontius Navigator
30th Jan 2018, 22:26
YT, our system was designed for a heat pump but the builder had difficulties selling the plan and had to use gas.

VP959
31st Jan 2018, 08:41
I see. I think you would agree yours is fairly unusual system albeit one that works very well in your circumstances. Thanks for the explanation.

It's a new build, so designed to cost virtually nothing to run (except for the blasted Council Tax) during our retirement, but not unusual, apart from having the Sunamp PV in place of a normal thermal store. It looks like a traditional house for the area (had to as it's within an AONB), but was just built using modern methods of construction, a bit like the way they've been building houses in places like Germany, Austria and Scandinavia for many years.

The building industry in the UK is probably 20 to 30 years behind some other countries, and slow to change. A lot of tradespeople we approached just refused point blank to quote, with the most common reason being that "We've been doing it our way for XX years and aren't about to change now", or something similar.