Hi, feels a little like im abusing the forum here as i havent posted in a couple of years as my build has been on hold due to family and now house building commitments, but i do keep browsing and ill be back on it before long

Anyway im after peoples experience of underfloor heating systems (wet, not electric) as were just finalising the drawings/specs to start building our new house in spring.
My main concerns are
-Is it worth fitting under a carpet? Im only considering it downstairs anyway (85mē) with radiators upstairs, and it will be ideal for the kitchen, dining and bathroom area (45-50mē) and future conservatory all with a hard floor surface, however we definitely want a nice carpet in the living room (35mē), which is going to limit its ability depending on how thick the carpet is. I dont want it to feel like a thin carpet when its brand new, but by the sounds of it, it takes ages for u/floor to heat up anyway so with a carpet insulating it, this must be made even worse? How noticeable is this in reality when living with it?
- do you have to leave it on all the time ie through the day when your out or through the night? ive been told this is something people dont tend to do which makes it less efficient and takes a while to heat up, but i cant see how it can be cheaper to run if you have to heat the house all the time? as opposed to just when your in with a conventional system
-Im considering fitting one radiator in the living room just to speed up the heating but wed really like to use the underfloor if its suitable as it makes the room so much more versatile for furniture etc.
-We will be using a conventional Gas, condensing boiler, rather than any of the ground or air source heat pumps as we cant afford them if that makes any difference.
-Also im seriously considering a heat recovery ventilator system for most of the rooms, any thoughts while were on the subject
Thanks in advance, all coments good or bad welcome.

[Edited on 4/1/14 by andrew-theasby]

with the underfloor systems ive worked on. they are very very good. they do take a while to heat up originally but as they dont really ever get swithched off they dont cool down.each room can be set at a different temperature and it can run the boiler at a much lower temperature than a radiator system due to the area the pipework covers.
usually a wooden floor/tiled floor is fitted but a carpet will be no problem at all.
if it can heat through a solid flag stone it will not struggle with a carpet. for some strange reason though,dogs do not like it? and will try to find somewhere cooler to sit/sleep
the economy is reached as you can set the rooms to the temps you want and the stats control the actuator heads independantly. so for example if you set your room stat to 15 degrees the boiler will run until the room is at 15 degrees,once this is reached the stat will close the actuator until the room drops in temperature which in turn shuts the boiler down. it will then not fire again until the room drops in temperature which could take ages due to the heat stored in the floor.
the boiler does not run all the time even though the system is on all the time if that makes sense. and it can run at a lower temp as stated above! cheers

quote:

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Originally posted by daniel mason
for some strange reason though,dogs do not like it? and will try to find somewhere cooler to sit/sleep

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the electric under floor/tile heating doesnt get as warm as the wet system though!

Hi bud, if you want to install carpet over UFH its no problem, just ensure you use the correct underlay
Ball & Young products are the way to go...http://www.underlay.com/underfloor-heating.html
cheers
Paul

Carpet will insulate and you should obtain the tog rating of any carpet you are proposing, and include this in the calculation of the heat emitter sizing. If you do not do this the output will be significantly reduced any decent UFH designer will ask you for this.

Also on hard floors any rugs also cause problems if not taken account of.

You need to expressly state the design parameters to any underfloor supplier, 21 degrees internally at -5 degrees outside with a flow temp at 42 degrees get this wrong and everything will go pear shaped too.

Surprised about the dogs, we recently designed a kennels for rescue chow dogs and was specifically asked to include underfloor heating.

Maximum output is about 100w/meter which is reduced depending on floor finish so if you have large heat losses (old property) this needs thinking about.

UFH operates at about 40/42 degrees and you can reduce the boiler temp down somewhat which will save energy and if it is weather compensated even better. But don't wind it down less than 60 degrees due to legionella issues in your hot water tank. The blending valve on the manifolds reduce the temp down by mixing the flow and return water to achieve the 40 degrees.

As you have already mentioned works great with air source heat pumps.

There is a lot of inertia when turning on/off.

Radiators are designed to work at much higher flow temperatures 85 degrees - any radiator installed and connected into the UHF circuit will need to be at least doubled in output/size.



[Edited on 4/1/14 by big-vee-twin]

Electric (resistive) underfloor heating is expensive to run.
Much better to use the electricity to drive a heat pump.

the upstairs rads will be on a different heating circuit via a zone valve i would think. meaning the tempreature inside them will be whatever the boiler is set too.unless your gonna have thermostatic rad valves on each rad.
as big vee twin said, the valve on the underfloor manifold controls the temp of the water circulating underfloor. the individual stats control the room temps by opening and closing their acutators on top of the manifold!

Thanks for the quick comments, raised a couple of questions though;

- if we are planning radiators upstairs, presumably we wont be able to turn the boiler temp down as well still need 85° there so will we not get the saving there? Also the tap water will want to be hotter than 60° wont it?

- when people refer to "not turning it off" is that the circulation pump then? as surely it turns itself off when its at temp, does the water flow all the time?

If you come home and the house is say 17°, roughly how long would you expect an underfloor heating system to take to reach say 20°, is it hours, or overnight? How slow is it really?

Thanks

Other half's friend has it, they love it.

They dug a load of pipes in under the garden and use a ground heat system, always toasty warm and very cheap to run. You can even get grants to pay towards it, the downside is a long long payback time.

I do not think they even bother heating upstairs as the house is well insulated, big house as well !

its a difficult one to say really how long as there are many variables.
the boiler does not need to be anywhere near 85 degrees for heating. the boiler can be set around 65degrees which will send that around the upstairs heating circuit via a zone valve,controlled by an upstairs room stat and a time clock (as the upstairs wont be on all the time because it will heat faster)
it will also heat the feed pipe to the u/f manifold to the same temp but these are usually very close to the boiled (usually next to it to keep wiring and plumming to a minimum. once it reaches the manifold there is a mixer valve like a rad valve to cool the temp around the under floor. the boiler is therefore not heating the whole underfloor circuits to 65deg.
ive seen people on here refering to groundsource too but you need a fair amount of land to dig the pipes in!

once the rooms at temperature the actuators on the manifold head close.stopping any flow through the u/f loop. when one room drops the actuator for that room opens,boiler fires,pump runs and it flows through that loop. its very good

Any issues locating the boiler up in the loft/second floor?

what about the cylinder and u/f manifold,zone valves,time clocks?
all needs wiring and plumbing so its easier to have it all located in a utility or similar. but its not out of the question to fit it where you like!

Google a company called Wundafloor, they do kits and are very helpful with questions, also good prices.

If you use radiators they will need to be oversized, physically get twice as big if not larger.

Tap water will take your skin off at 60'its quite hot.

Regarding keeping permanently on, this mainly applies to heat pumps as unlike other heating devices their capacity to heat reduces as the external temp reduces, so struggle to warm up a clap cold house.

If you size the system correctly it will warm up from clap cold in 2 to 3 hours.

quote:

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Originally posted by andrew-theasby

Thanks for the quick comments, raised a couple of questions though;

- if we are planning radiators upstairs, presumably we wont be able to turn the boiler temp down as well still need 85° there so will we not get the saving there? Also the tap water will want to be hotter than 60° wont it?

- when people refer to "not turning it off" is that the circulation pump then? as surely it turns itself off when its at temp, does the water flow all the time?

If you come home and the house is say 17°, roughly how long would you expect an underfloor heating system to take to reach say 20°, is it hours, or overnight? How slow is it really?

Thanks

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quote:

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Originally posted by daniel mason
its a difficult one to say really how long as there are many variables.
the boiler does not need to be anywhere near 85 degrees for heating. the boiler can be set around 65degrees which will send that around the upstairs heating circuit via a zone valve,controlled by an upstairs room stat and a time clock (as the upstairs wont be on all the time because it will heat faster)
it will also heat the feed pipe to the u/f manifold to the same temp but these are usually very close to the boiled (usually next to it to keep wiring and plumming to a minimum. once it reaches the manifold there is a mixer valve like a rad valve to cool the temp around the under floor. the boiler is therefore not heating the whole underfloor circuits to 65deg.
ive seen people on here refering to groundsource too but you need a fair amount of land to dig the pipes in!

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Ok, thanks for the pointers, ive got some good reading to do now tonight thanks.

Hi,
I've built and lived in2 houses with self designed and installed underfloor heating. The response time is determined by the thermal capacity of the screed and there is a minimum thichness of around 60 mm ur there is a risk of cracking.

I've used 100 mm thick screeds and it takes ages to warm and cool down which makes it tricky if the weather changes quickly. I ended up in one case using the underfloor heating as background heating with log fires to top up.

You can also use screedless uf heating using spreader plates under timber floors and the response is very quick indeed.

On both cases very comfortable and economical but capital cost was toughly double.

Cheers!

Thankfully with modern screeds you can now go down much thinner giving a faster reaction time.

It would be worth you talking to one of the main suppliers, try JG Speedfit. They provide a design service for their products.

I am in the process of commissioning mine, 5 zone underfloor and all rads upstairs individually controlled.

Installation was easy, took me one day to mark out and one day to lay.

I take it that this is new build, as retrofit is as lot of hassle and you don't get the insulation depth.


If you want to have a look at the system design drop me a u2u with your email address.

Regards roger