Floor not getting warm...

[Matthew Kitching]

Morning,

Will try and keep as brief as possible.

Have recently undertaken a barn conversion and have had a ground-source heat pump installed with UFH. I have been concerned for quite some time that the floor doesn't feel warm, despite the UFH being turned on. I have the room thermostats set a 20 degrees. I don't really want to turn them up anymore as the house is so well insulated we will end up baking !

Should I be feeling the heat through the tiles at 20 degrees ?

My builder had a few "issues" whilst installing the pipes and laying the screed as the floor levels were very hit and miss with it being an old barn. I think in certain areas we have 110mm, but most areas I believe are around 75mm. Could this be an issue ?

I have spoken to my UFH installers and they are suggesting I turn the heating up to 25 or 26 degrees but obviously I am loathed to do this...

Any advice greatly appreciated.

 

[Ajax123]

firstly the speed at which it heats and cools will be dependent heavily on the screed type used. If it is sand cement it will take several hours to get up to temperature. It will also depend on the flow temperature you are running thorough the pipes. If they are standard 16mm pipes and sand cement screed I would anticipate that you will need a flow temperature of around 45 to 50 degrees to get any sort of sensible output. the ground source heat pump should be capable of delivering this sort of flow temperature. finally the screed should not feel "warm" to the touch. this is a mistake that many many people make. It should at best feel tepid and not freezing cold. If you think about it your body temperature will be around 37degrees and the skin temperature on your hands probably around 30. If the floor is running a surface temperature of anything less than this the it wont feel warm to the touch. To get a room to 20 degrees on a room stat you will likely need a surface temperature of around 26 degrees and a flow temperature of around 45. if you run it much warmer than this it will not only be inefficient but also flipping uncomfortably warm.

So I guess it depends on what you are expecting in terms of it being "warm"

 

[J Sid]

probably wouldn't feel very warm to the touch at 20, but will heat the room ok
get one of these to test for yourself
https://www.amazon.co.uk/gp/aw/d/B0...ture+laser&dpPl=1&dpID=51xkGJ1D1ZL&ref=plSrch

 

[Matthew Kitching]

firstly the speed at which it heats and cools will be dependent heavily on the screed type used. If it is sand cement it will take several hours to get up to temperature. It will also depend on the flow temperature you are running thorough the pipes. If they are standard 16mm pipes and sand cement screed I would anticipate that you will need a flow temperature of around 45 to 50 degrees to get any sort of sensible output. the ground source heat pump should be capable of delivering this sort of flow temperature. finally the screed should not feel "warm" to the touch. this is a mistake that many many people make. It should at best feel tepid and not freezing cold. If you think about it your body temperature will be around 37degrees and the skin temperature on your hands probably around 30. If the floor is running a surface temperature of anything less than this the it wont feel warm to the touch. To get a room to 20 degrees on a room stat you will likely need a surface temperature of around 26 degrees and a flow temperature of around 45. if you run it much warmer than this it will not only be inefficient but also flipping uncomfortably warm.

So I guess it depends on what you are expecting in terms of it being "warm"

Thank you for your reply.

We used an anhydrate screed.

I will check the flow temperature on the heat pump but I think it is set around 50 degrees.

I don't know if I'm expecting too much but was expecting the floor to feel warm on my feet. We have UFH in the bathrooms and the floors get lovely and warm on bare feet.

Will get hold of a laser thermometer and take some readings of the floor temps and report back.

 

[Tile Shop]

One more thing to check,

Not going to tarnish all builders with the same brush, but a few of them think that dotting and dabbing floor tiles is acceptable. If your builder is one of these chaps, you will have voids beneath the tile that will drastically effect the heat transfer to the surface. (we've seen this many times before)

See if any of the tiles sound hollow and ask the builder to confirm how the tiles were laid. If they have been D&D'd you'll be fighting a loosing battle. But if he confirms he spread the adhesive and got full coverage, then as above. Trial and error. Boost the temp til it feels "comfortable" and try not to bake yourself in the process 🙂

 

[widler]

Is it tiled ?

 

[DavidP-TUFHS]

The type of pipe and the centres will play a big part here too.

 

[J Sid]

the floor temp will depend on the available floor area in relationship to m3 of room area and how well the room is insulated.

 

[Ajax123]

If it feels warm under foot its probable too warm. That's ok for a bathroom where you only spend a short time with your feet on the floor but if its too warm through the whole house it can lead to health problems. Hot heated floors have been tentatively linked to thrombosis. If it is Anhydrite the flow temperature will need to be around 40 this tie of year assuming your insulation is reasonably good. the thermal conductivity of the screed remains constant regardless of depth but the mass (used to create thermal inertia) is obviously grater so slows the response down a little. I have 90mm in one of my rooms and it does take a while to warm up the room but once it is there the floor doesn't feel warm. don't get me wrong...its not that horrid freezing cold you get on uninsulated concrete or ceramic tiles but is not warm either.

 

[Chalker]

Forget the temperature of the floor. This should on ground source, be only mildly warm to toutch. It's the air temperature that matters. Does it reach 20degrees? If so its working fine, if you want the air temperature warmer, turn it up.dont forget on air source, it's a 24/7 heating demand.
If not, then you have a problem! Either the heat pump needs comisioning properly , or issues with trapped air in the ufh loops.
Ps.do you live in the Hartogate area! I know a Mathew Kitchen there.