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Discuss UFH costing a fortune to run in the Water Underfloor Heating Installations area at

I have had UFH fitted to an extension approx 50m2. I believe the screed depth is 100-130mm with 100mm kingspan PIR beneath. The system as a whole takes a long time to affect the room temperature, it is set to come on at 6am and by 11am in may have raised the temp by 1-1.5degrees. It is also costing around £4 a day to run (according to a smart meter) and I have seen my utility bills nearly double.

I know there are many variables that effect the running costs of UFH but this seems out of control. Any advice as to why it may be costing so much and what I can do to help reduce it.

I have a HIVE thermostat with water temp set at 45degrees with the rom temp set at a min of 20.5 going up to 22 at times through the day. Thanks.


Staff member
S. Mod
Gas Engineer
:D sorry to say there's your problem maximum screed depth for ufh is around the 50mm mark normally it's a lot less than that

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What matters is the thickness the manufacturer / designer of the UFH has used in the calculations.

What pipe system is it and who designed it?


Staff member
S. Mod
Gas Engineer
Most UFH stockists state 60-75mm minimum screed dept???
I would say that is your about right depth for sand and cement screws depth liquid screed depth normally a lot thinner

As the thinner it is the less engy it requires to heat it up, so there's your problem I think

Direct from a manufacturer

"An underfloor heating system in concrete relies on the thermal conductivity of the screed to transfer the heat to the rooms. It may be a slow response system, so the underfloor heating should be on 24/7 during the heating season with setback options available. It is recommended to use programmable room thermostats for extra comfort."

Matthew Score

Gas Engineer
There are many factors which affect UFM heat up times and running costs!

I would presume the extension was built to current building regulations in regards to insulation and overall heat loss for the extension.

Did the UFH company design your system, ie pipe lay out, including pipe spacings, provide screed depths for the screed type you have used?

What floor covering is on top of the concrete slab?

(Tiles and laminate are best suited to UFM, carpets can be used but the UFH manufacturer normal advise on the maximum tog valve of carpet that can be used.)

What temperature is the blending valve set to?
Last edited:


Advent Win
Liquid screeds running at 30 to 45mm depth.

That's some thermal load at 4 to 5" deep screed. Somebody's screwed up.


Here's something to try.

Ditch the Hive thermostat and put a manual thermostat and set it to 21 C constantly.
The Hive thermostat may be altering the systems operation due to its 'intelligence of the local weather and predicted weather'.

Your system may not have been allowed to operate fully due to the Hive thermostat

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