Underfloor heating installed without insulation

[cgencer]

My builder recently installed a Polyplumb solid floor type underfloor heating in our house. The pipes were put on the concrete floor and then topped up with about 75mm of screed. Unfortunately at the time I did not realize you had to put insulation directly under the pipes as well. The house is built in 70s so there is a damp proof membrane and supposedly insulation on top of that and that is why he did not put any further insulation.

The heating seems to work OKish at the moment on bare screed floors, and after some time can reach around 20-21 degrees with 55 degrees flow temperature. The boiler flow temperature is set at 75 degrees. but I'm worried about the running costs if a lot of heat is being wasted heating the concrete floors up. Is this something to be worried about or not?

 

[lame plumber]

not a lot you can do now. bigger bills than if you followed building regs specs, but hey ho

 

[Gray0689]

My builder recently installed a Polyplumb solid floor type underfloor heating in our house. The pipes were put on the concrete floor and then topped up with about 75mm of screed. Unfortunately at the time I did not realize you had to put insulation directly under the pipes as well. The house is built in 70s so there is a damp proof membrane and supposedly insulation on top of that and that is why he did not put any further insulation.

The heating seems to work OKish at the moment on bare screed floors, and after some time can reach around 20-21 degrees with 55 degrees flow temperature. The boiler flow temperature is set at 75 degrees. but I'm worried about the running costs if a lot of heat is being wasted heating the concrete floors up. Is this something to be worried about or not?

Yes it's done completely wrong by the sounds of it
Is there a underfloor thermostatic mixing valve fitted for manifold
Can you post some pictures please

 

[CMcM]

slowly increase the heat to the screeded floor bud, hitting it straight away with high temps could cause the screed to crack.

 

[cgencer]

Here is a picture of the manifold..

Screed is been there about 3-4 weeks before we turned on the heating. However considering the screed is already put in, what's our options here. The builder claims there was already insulation under the concrete floor, that's why he didn't put any in. How much more gas usage are we talking about here? Would putting an overlay system on top of the screed be a more efficient option (given I can get him to put it in for free)..

 

[Gray0689]

What sort on insulation was already in
Sand cement screed needs approx 6 weeks to dry before underfloor goes on
What temp is underfloor running at?

 

[cgencer]

What sort on insulation was already in
Sand cement screed needs approx 6 weeks to dry before underfloor goes on
What temp is underfloor running at?

It is running at 55C. I'm not sure what kind of insulation there already was in.. I don't think it's been 6 week. More like 4.

 

[Gray0689]

If its wrong insulation
It's going to cost a lot more to run

 

[cgencer]

He doesn't seem to know what kind of insulation it is. Is there any way to find out? Would an overlay system be more efficient?

 

[Gray0689]

As in an electric overlay
I don't now

 

[cgencer]

As in an electric overlay
I don't now

No the wet one..

It's called Polyplumb overlay

 

[DirksPlumbing]

No the wet one..

It's called Polyplumb overlay

Sounds like you got the real _under_ floor heating. Just bump up the flow temperature until you get a comfortable heat to the house and take a note of the gas reading for a few days (fortnight). Post those numbers and you will be able to get a guestimate of your annual cost.

And an estimated insulation value of your floor. Just to mention that the insulation thickness typically used in GB is well below requirements of other European countries. And often even PU based insulation is used which is hygroscopic and therefore likely to be considered as non existing.

Wonder how UFH could get such a bad reputation?

Should there really be insufficient insulation under then you still got the chance if the ground is dry that it will saturate over the years.

 

[DirksPlumbing]

Here is a picture of the manifold..

I like those slim shaped controls/actuators. Wireless?

 

[cgencer]

I like those slim shaped controls/actuators. Wireless?

There aren't any actuators.. The bottom ones are flow meters and the top ones are plastic valve caps..

 

[hydrotherm]

Typical builders attempt at plumbing.

 

[cgencer]

What would your suggestion be? The best we can try to do is to get our money back from the builder. And then what though? Scrap the whole system and install radiators? Have somebody actually qualified to put in a wet overlay system?

Taking out the screed and redoing the whole thing over again is likely to take a lot of time..

 

[dancinplumba]

Where are the controls ? Room stats ? One to control each zone ? All wants ripping out and doing properly with insulation 🙂

 

[cgencer]

Yes there is an ordinary non-digital honeywell roomstat. It's a big single room (open plan kitchen/living room) so there is a single stat. Two of the four zones on the manifold are used but they are all turned on/off at the same time through the stat(which is fine as it's a single big room).

 

[dancinplumba]

If only 2 of the zones used what are the other 2 for ? And where are the actuators for used two zones ? This is a right cock up

 

[cgencer]

The other 2 are disconnected/ not connected to anything. As I said there are no actuators.. What are the actuators used for? It was said that they were not needed as it is controlled as a single zone..

 

[cgencer]

Sounds like you got the real _under_ floor heating. Just bump up the flow temperature until you get a comfortable heat to the house and take a note of the gas reading for a few days (fortnight). Post those numbers and you will be able to get a guestimate of your annual cost.

And an estimated insulation value of your floor. Just to mention that the insulation thickness typically used in GB is well below requirements of other European countries. And often even PU based insulation is used which is hygroscopic and therefore likely to be considered as non existing.

Wonder how UFH could get such a bad reputation?

Should there really be insufficient insulation under then you still got the chance if the ground is dry that it will saturate over the years.

Thanks.

The house seems to get reasonably warm.. About 20 degrees. If l turn off the system around 11pm, and turn it on at 6am, it takes about 2 hours to get back to 20 degrees. But there are no floors above the bare screed at the moment. I'm not sure how it will be after putting on the wooden floors.

Gas Usage I've only measured for two days now. It's 9087 and 9090. However there are an additional 3 radiators upstairs and some hot water usage (shower) as well.

If you had a chance to fix it what would be the best option?

 

[dancinplumba]

The other 2 are disconnected/ not connected to anything. As I said there are no actuators.. What are the actuators used for? It was said that they were not needed as it is controlled as a single zone..

What is the stat wired to ? Does it turn on the underfloor ? It should turn on the zones via the actuators.
What heating have you upstairs ?

 

[cgencer]

What is the stat wired to ? Does it turn on the underfloor ? It should turn on the zones via the actuators.
What heating have you upstairs ?

There is a valve under the boiler that turns off flow to the manifold. The thermostat is connected to that. There aren't individual actuators on the manifold for each circuit..

Upstairs is 3 radiators + 1 towel rail which are controlled by a separate stat and valve.

 

[Howsie]

What is the stat wired to ? Does it turn on the underfloor ? It should turn on the zones via the actuators.
What heating have you upstairs ?

That is probably one zone on the manifold.

 

[Gray0689]

That is probably one zone on the manifold.

4 zones I one room must be very big then and a doubt it

 

[Howsie]

It's not unusual in smaller properties IMHO.

 

[Gray0689]

The hole idea for underfloor is control of zones ie each room controlled by room stats and actuators

 

[Howsie]

The idea of UFH is to heat rooms. You don't have to have actuators to do that.

 

[Gray0689]

No point going to the trouble of doing it and not controlling it in my opinion

 

[Howsie]

In all honesty, most people never touch the stats once they've found a comfortable temp and that's what these cheap and simple kits provide. No ideal, but they have their p,ace.

 

[erj]

idealy yes dig up the floor put in 50mm king span and start again, but this is not going to happen. two hr to heat up sounds about right in my expariancs, open plan controlled be state and zone valve nothing wrong with that.
Yes the job is not prefert but the diffrance in gas bills will not be noticable and do you want to fall out with the builder?
we have just done a simlar floor (done right with instaltion) with a wood floor on top and it works fine wood not hot but the room is 20/21c no problem.
Personly I think you are worrying to much and have been watching to many builders from hell on the telly, like a lot of customers and think we are all trying to rip them off

 

[DirksPlumbing]

idealy yes dig up the floor put in 50mm king span and start again,...

Ideally Kingspan is never found underneath a screed. Ideally it is a 1" to 30mm sound insulation and underneath 2"+ of load bearing polystyrene minimum and a damp proof course + expansion strips round the walls.

But yes, if you only read 3cbm of gas there is no reason to worry, the controls are more than basic and will require you to shift times all over the year but with a programmable roomstat (CM907?) this would improve. 3cbm a day is a steal.
Equals to roughly 36kW. And this at the current temperatures! Doubt you would get it much better without spending high 4digits.

But a wooden flooring has to be seen as an additional layer of insulation on top of your heating which will shift thermal conditions dramatically. Make sure that its flooring suitable for UFH (clamped with springs underneath) otherwise your joiners better get a spare room set up.

Had a case where 1" Kingspan (soaking wet) been under the pipes and 40+mm of wooden flooring above. You can guess where the heat went. Mice were running naked all winter, customer was ready to burn the hard wood flooring to at least have heat once.

 

[Bronze_tap]

What would your suggestion be? The best we can try to do is to get our money back from the builder. And then what though? Scrap the whole system and install radiators? Have somebody actually qualified to put in a wet overlay system?

Taking out the screed and redoing the whole thing over again is likely to take a lot of time..

1. I would rater insulate the walls+foundations on the outside of the house, so there is less direct heat escape route,
2. Use it as a BIG mansonry stove - ditch the timer (or extend on time signifficantly), and set it to be always on the room thermostat, also try reducing the boiler flow temp a bit, so it modulates down, but make sure it doesn't cycle.
3. You can have the rads piped in series with the UFH, so the water first cools in the rads, and then becomes really chilly in the floor. This would max out the condensing boiler efficiency. Also can have an option of bypassing the rads or the UFH (takes a ~half dozen of the gate valves and a few tees).

4. Your's meter(wallet) and room thermometer will clearly tell you what is the best settings... But with 3 cubes a day you're doing really well at 0 outside + 20mph wind 🙂

 

[SimonG]

The writing was on the wall with this one with the first sentence 'My builder installed'.

Tell your builder he's screwed it up and ask him what he's going to do to fix it. Then take it from there.

 

[AWheating]

if no insualtion was used im guessing the pipework was not pressurised when the screed went down?

plumbers do pipes, builders try to do pipes.

 

[Plumbum1]

Own fault never get a builder to do a plumbers job clown!

 

[Howsie]

Own fault never get a builder to do a plumbers job clown!

Goodbye.

 

[Gray0689]

Ideally Kingspan is never found underneath a screed. Ideally it is a 1" to 30mm sound insulation and underneath 2"+ of load bearing polystyrene minimum and a damp proof course + expansion strips round the walls.

But yes, if you only read 3cbm of gas there is no reason to worry, the controls are more than basic and will require you to shift times all over the year but with a programmable roomstat (CM907?) this would improve. 3cbm a day is a steal.
Equals to roughly 36kW. And this at the current temperatures! Doubt you would get it much better without spending high 4digits.

But a wooden flooring has to be seen as an additional layer of insulation on top of your heating which will shift thermal conditions dramatically. Make sure that its flooring suitable for UFH (clamped with springs underneath) otherwise your joiners better get a spare room set up.

Had a case where 1" Kingspan (soaking wet) been under the pipes and 40+mm of wooden flooring above. You can guess where the heat went. Mice were running naked all winter, customer was ready to burn the hard wood flooring to at least have heat once.

Why not kingspan
Ideally should be 100mm of a celotex insulation

 

[Si H]

Should be road stone or concrete then damp membrane then 100mm cellotex/ Kingspan then ufch under approx 50-65mm screed.
It's been done wrong all you are doing is heating the floor mass under the house which will then spread outside the building. Overlay UFCH is good and kicks out approx 125 watts per sq metre at 50 deg c.
Use both systems all the time and work great with gas and even better with ashp

 

[Si H]

And also forgot to add membrane between the celotex or Kingspan and screed as the screed rots the the insulation

 

[cgencer]

Ideally Kingspan is never found underneath a screed. Ideally it is a 1" to 30mm sound insulation and underneath 2"+ of load bearing polystyrene minimum and a damp proof course + expansion strips round the walls.

But yes, if you only read 3cbm of gas there is no reason to worry, the controls are more than basic and will require you to shift times all over the year but with a programmable roomstat (CM907?) this would improve. 3cbm a day is a steal.
Equals to roughly 36kW. And this at the current temperatures! Doubt you would get it much better without spending high 4digits.

But a wooden flooring has to be seen as an additional layer of insulation on top of your heating which will shift thermal conditions dramatically. Make sure that its flooring suitable for UFH (clamped with springs underneath) otherwise your joiners better get a spare room set up.

Had a case where 1" Kingspan (soaking wet) been under the pipes and 40+mm of wooden flooring above. You can guess where the heat went. Mice were running naked all winter, customer was ready to burn the hard wood flooring to at least have heat once.

I should have said its 3 units in imperial gas meter, not 3 cubic meter (we have an old imperial gas meter), so it's about 96kwh instead.. I've turned off the underfloor now and the usage has dropped dramatically.

 

[cgencer]

Thanks very much for all the replies. To give you guys an update, he realized he did something wrong and offered to fit the JG Speedfit underfloor heating for free. It's an overlay system 25mm thick. Anybody have experience with this? Besides that I've gotten some quotes to fit a Polypipe overlay system as well, which is another possibility.

 

[Gray0689]

Well
At least he is trying to fix his mistake
The overlay should be fine just go by the manufacture specifications with insulation ect

 

[Howsie]

Get it in writing before he touches anything.

 

[Rickster123]

A builder working for free?? Please come back and update us if.... I mean when it gets done!

 

[Si H]

Both systems Speedfit and Polypipe are good. Your builder will get a surprise tho its about double the cost of standard UFCH 🙂

 

[cgencer]

I think this is the board he wants to use: [DLMURL="http://www.speedfitufh.co.uk/overfitboard.php"]Overfit (Over floor) Board | The Speedfit Underfloor Heating System[/DLMURL] , and seems there is no need for additional insulation.

 

[Si H]

Yep overlay or overfit. May be a Good idea to put extra reflector under it too, the double silver sided bubble wrap type just to give it extra oomph so to speak!

 

[DirksPlumbing]

Why not kingspan
Ideally should be 100mm of a celotex insulation

Because the Kingspan in use is Polyurethan and aluminium foil. As stated before contact to screed rots the tinfoil away in no time. And Polyurethan is hygroskopic which means it tries to take in as much humidity as it can. What that does mean to an insulation board most likely packed between two layers of wet concrete with no meaning to vent away one might figure out himself.

 

[SimonG]

I always thought kingspan was a brand of celotex?

 

[Gray0689]

I always thought kingspan was a brand of celotex?

Me too