Underfloor Heating

bugsy91

I bought my house just before lockdown in April which has underfloor heating on the entire ground floor. I switched it on to check it was working when I first moved in but haven't touched it since. Now the colder months are approaching, I'm wondering what's the best way to utilise it? My feeling is that once it's turned on, not to turn it off again until next year as it would be more efficient to heat it once and then maintain? There are thermostats in each room but not 'smart' if that makes any difference? Anyone whose got this, what's your usual winter routine? Thanks

daveyjp

Parents have it and once winter comes they set the room stats with day and overnight temperatures and leave it.  The concrete screed is the heat sink so it needs warming up.

The weak link on their system are the room stats.  I noticed last year the heating was cycling, but no stats were on.  One of the bedroom stats had failed and was calling for heat.

Cardew

What sort of UFH - electrical? or hot water? If the latter how is the water heated?

bugsy91

Cardew said:

What sort of UFH - electrical? or hot water? If the latter how is the water heated?

Hot water heated by the boiler.

bugsy91

Mickey666 said:

Just think of the UFH as a large radiator that takes a while to heat up and cool down.  If you leave it on 24/7 throughout the winter months you'll use more energy, just as you would if you left a conventional central heating system on all winter.

I don't leave my UFH on all the time, I simply adjust the timer to account for the lag in warming up and cooling down, which you'll quickly learn through trial and error.  Mine seem to lag by around 4 hours.  Thus, I set it to come on at around 5am so that things are nicely warm by the time I get up around 9am and I set it to turn off around 8pm.

Perhaps try a simple test of using a timer for one month and leaving it on 24/7 for a month (though be careful to take into account average outdoor temperatures).

I did think about this, with the lag time. During the week I'm out the door at 7:30am and back around 6. So it's whether it would be better to have it come on around 5 then knock off at 7:30, then back on again an hour or so before I'm home, and off for bed? Or whether this would be inefficient due to the short time periods. As you say, I think so trial and error will be needed.

tim_p

Is it a gas heated wet system or is it electric?

bugsy91

tim_p said:

Is it a gas heated wet system or is it electric?

Gas heated

Talldave

bugsy91 said:

Mickey666 said:

Just think of the UFH as a large radiator that takes a while to heat up and cool down.  If you leave it on 24/7 throughout the winter months you'll use more energy, just as you would if you left a conventional central heating system on all winter.

I don't leave my UFH on all the time, I simply adjust the timer to account for the lag in warming up and cooling down, which you'll quickly learn through trial and error.  Mine seem to lag by around 4 hours.  Thus, I set it to come on at around 5am so that things are nicely warm by the time I get up around 9am and I set it to turn off around 8pm.

Perhaps try a simple test of using a timer for one month and leaving it on 24/7 for a month (though be careful to take into account average outdoor temperatures).

I did think about this, with the lag time. During the week I'm out the door at 7:30am and back around 6. So it's whether it would be better to have it come on around 5 then knock off at 7:30, then back on again an hour or so before I'm home, and off for bed? Or whether this would be inefficient due to the short time periods. As you say, I think so trial and error will be needed.

If the thermostat has a decent optimum start feature with a really long "advance" capability (to cope with the UFH lag), you can set the actual target times you want and let it compensate. Otherwise, you'll have to keep tweaking the "on" time back the deeper into winter we get as the lag increases. 

The other compromise is not to switch it off at night/daytime but set it to a lower temp that stops it cooling too much. Then it won't take so long to get back up to temperature when you want your "at home" temperature. I would guess that this approach will use more gas, but unless you can find two weeks with identical weather it's impossible to do a comparison. 

Our house has UFH in new extension parts and traditional radiators elsewhere.  The insulation is so good in the UFH areas that my feeling is that it's the radiator areas that use all the gas. But the UFH thermostats have a max 2 hours optimum start which is not really enough.

matelodave

I've got wet underfloor heating all over and each room has a thermostat which controls the flow valves feeding the room. They are all programmable stats so I can have different temps in each room at different times of the day.

As said above, there's a definite time lag between when the heating comes on and the room comes up to temp as well as cooling down depending how thick the slab is. Ours is an overlay system so a bit more responsive, but still very slow as have very low flow temperatures (30-40 degrees) because we've got a heat pump. We never let the place get stone cold as it can take over a day to get back up to temp. All our stats set back to 17 degrees overnight and to working temp during the day depending on the room a couple of hours before we use it and then down again about an hour or so before we've finished.
Example - bedroom & bathroom 0600-0900 and then 2000-2200, Lounge 0700-2100, Study 0700-1700. The hall and kitchen usually stay at 17 degrees all day and night and the spare room is set for 15 degrees unless it's being used

We find that as the whole floor is warm, we don't tend to get cold draughts, so the rooms feel warmer at a lower temperature

Penelopa.Pitstop

bugsy91 said:

I did think about this, with the lag time. During the week I'm out the door at 7:30am and back around 6. So it's whether it would be better to have it come on around 5 then knock off at 7:30, then back on again an hour or so before I'm home, and off for bed? Or whether this would be inefficient due to the short time periods. As you say, I think so trial and error will be needed.

We had heating setup to start at 3.30am and switch off at 6.30am with temperature to reach 20C. And then again from 14.30 until 18.00. In between these hours, we had thermostat setup at 18C. If temp is 20C or above, heating won't switch on in its scheduled window.
I don't like my UFH but it was already in the whole house, so don't exactly have a choice. I don't think setup works correctly, etc. I would rather have radiators.