Underfloor heating

meoldchina, Apr 16, 10:57pm
What is the optimum temperature setting for underfloor heating in a bathroom? Also, would it be more efficient to leave it running 24-hours, or timed to come on for just a few hours each day?
cagivachick1, Apr 16, 11:59pm
if its a digital controller set it on 20 and leave it on 24/7
merrigj, Apr 17, 12:17am
Do you have night rate electricity?
jonners2013, Apr 17, 2:56am
however high it needs to be to make the room warm enough to be comfortable. or was this a trick question?
stevo2, Apr 17, 3:06am
We set ours to 22 degrees. Ensuite is wooden floor and turns on an hour before we get up and stays on till we go to work. Wooden floor heats up quickly and cools down quickly as well.
Main bathroom is concrete floor an set to 21 degrees and comes on 2 hours before anyone is awake. It turns off an hour before they leave in the morning. It takes longer to heat up but retains the heat when turned off.
If you are home all day, leave it on at a lower but comfortable temp.
meoldchina, Apr 17, 4:04am
No, we don't have night rate electricity.
aredwood, Apr 18, 6:39am
Far cheaper to just set the timer for it to come on when needed. It is an electric heating element. And due to the thermal mass of the floor it behaves like an oil column heater. Which means when you switch it on it starts using power immediately. But you have to wait for the floor to heat up. And when you switch it off it still keeps releasing the heat that has built up in the floor.

So with cleaver use of the timer you can keep power usage low. But still keep the floor warm.
cagivachick1, Apr 18, 2:32pm
if its a older house with wooden floor there is no thermal mass, total thickness would be 40mm, 25 of that wood, its a good idea to insulate under the floor if you can to hold the heat or instead of using TnS underlay use something like F board to block the heat
meoldchina, Apr 18, 8:31pm
Thank you for your comments. It is a modern house with good insulation and the heating is under tiles, so I think I will go with aredwood's recommendation and use the timer. It will be interesting to see what happens to our power bills.
tintop, Apr 19, 3:29am
Yes - it is false economy to leave it on 24 hours.
Just experiment with the timer, find the best on/off times to suit.
cagivachick1, Apr 19, 9:15pm
how is it false economy to have a constant heat ? do you turn your hot water cylinder on and off just before you want to have a shower? our ensuite and dining room floors are set at 20 and on all the time costs about $20 a month, any way your choice
tintop, Jan 30, 1:19am
Hot water cylinders are on for convenience, as well as that they are well insulated so heat loss is minimised.

If under floor heating s on 24/7, then there is ongoing heat loss 24/7.

If the floor heating is turned off for say - during the day and over night when not in use, once the floor has cooled there is no further heat loss. The amount of power to reheat for morning ( and evening) is way less that what would be used otherwise.

Isaac Newton was a clever chappie, not only did he wonder about gravity, but he also worked on heating and cooling. Google 'Newtons law of cooling'

You mentioned hot water cylinders which is not really a valid comparison, but - compare what I said to a car. Do you leave it idling over night ? Or an electric heater running 24/7 ?

And I have difficulty believing your cost of $20 / month.

A 100W light bulb running for a month would cost nearly that much if it ran 24/7 at $0.24 / kWh.