New house with underfloor heating - How do you set yours up?

[anonymous-user]

Hi all,

I'm in a new house which was built this year, and as such it is stuffed to bursting point with over-spec insulation, and has underfloor heating downstairs and radiators upstairs.

The last house I lived in had radiators throughout, a crappy boiler, piss poor insulation, a single old fashioned rotary dial thermostat, and an impressive selection of draughts. When the weather was cold, the heating ran constantly to keep the house warm, and when it switched off at 11pm at night, the house went quite cold.

Given my last experience was quite different, I have no idea how to set the heating controls on the new house for warmth and efficiency.

The new heating system has a digital thermostat in each room or each zone, all linked by wifi, and these are all controlled by a Salus Smart Home app on my phone.

Should I leave the under floor heating on all the time? Should I set it to go off during the night like I used to?

Any other tips for setting the zones/times/temperatures?

Do I just leave the hot water heating on all the time as well? It is a pressurised system with one of those large insulated hot water tanks.

Edited by anonymous-user on Wednesday 6th October 13:18

[Ranger 6]

We only had UFH in the kitchen in our last house, however it was 50 sq m. The thermostat was programmed to go low (16 Degrees) through the night and then stick at 21 degrees through the day.

As the seasons progressed through the year it was probably only on for four months.

I'd say set it and leave it. Adjust the radiators to suit.

[Lotobear]

i'd have a word with the builder

[anonymous-user]

Lotobear said:

i'd have a word with the builder

He has shown me how it all works, however I felt it best to get tips from others who actually live with this sort of system.

[Pinkie15]

UFH is designed to be set to a temp and left at that; it runs at a lower water temp than rads; something like 40 deg cf rads at 80 odd degs.

We have UFH in our kitchen/diner, @80 sq m in 2 zones. We run ours at an indicated 22.5 deg (dial rather than digital thermostats). When set to just under 22 it feels like it’s off, at 23.5 it’s like a sauna. Depending on your floor type, we have ~75mm screed over ours, it takes a day or so to heat up. Conversely it takes a day or so to cool down. Apparently cos of the thermal mass of the screed (it’s like a giant storage heater). It’s not ‘agile’ to rapid changes in room temp like rads.

We too have closed/pressurised hot water system, just do a morning and evening heat cycle for about 1.5 hrs each time.

[Biggus thingus]

Everyone lives differently so the best way i found was trying different settings to see which worked out best

If the house is empty during the day let the temp drop back to the set back temp and then set it for comfort temp when the house is occupied

[anonymous-user]

Pinkie15 said:

UFH is designed to be set to a temp and left at that; it runs at a lower water temp than rads; something like 40 deg cf rads at 80 odd degs.

We have UFH in our kitchen/diner, @80 sq m in 2 zones. We run ours at an indicated 22.5 deg (dial rather than digital thermostats). When set to just under 22 it feels like it’s off, at 23.5 it’s like a sauna. Depending on your floor type, we have ~75mm screed over ours, it takes a day or so to heat up. Conversely it takes a day or so to cool down. Apparently cos of the thermal mass of the screed (it’s like a giant storage heater). It’s not ‘agile’ to rapid changes in room temp like rads.

We too have closed/pressurised hot water system, just do a morning and evening heat cycle for about 1.5 hrs each time.

Thank you, that is really helpful.

My UFH is under a 65mm screed, so yes, I was expecting it to act like a giant storage heater. I will set it to a constant temperature and see how I get on, and adjust it for there. It has been 'default set' to 22c by the builder and the house is overly warm, so I have set it to 20c and will go from there.

With regards to hot water, there is only myself and my wife, so I think as you suggest, a 1.5 hour heating of the water morning and evening will be fine.

Edited by anonymous-user on Wednesday 6th October 14:17

[Andeh1]

Yes, set it for 22 degrees when you need it, and 19/20 when you don't and just leave it.

You won't need 3 hours of water heating per day! Hour before shower/bath, 30mins in the morning. That should be sufficient.

[anonymous-user]

Andeh1 said:

Yes, set it for 22 degrees when you need it, and 19/20 when you don't and just leave it.

You won't need 3 hours of water heating per day! Hour before shower/bath, 30mins in the morning. That should be sufficient.

Thank you

[outnumbered]

We have a similar setup, highly insulated house, full UFH downstairs with a zone for each room.

Ours is programmed to go off overnight, as I don't see the point in keeping downstairs fully warm when there's nobody there. It comes on fairly early in the morning as it's not instantaneous heat. I'm sure it's cheaper to run it this way (by the same argument that it's cheaper to heat the hot water only when you need it).

You might find that you don't need to run the heating in all the rooms. We have one reception room which stays at 20-21C without needing to turn the UFH on at all, and we actually rely on the Plasma TV to heat the room up a little more if we're using it ! We also have a room that gets a lot of solar gain, and that one is set up so that the UFH doesn't try to do much until mid-morning, so if the sun's out, it then doesn't need to come on fully until late afternoon.

[Pinkie15]

Re the hot water; should have said that we’re a house of 5 (me, missus, 3 teenage daughters).

I go for the 1.5 hr spread as it allows for various showering regimes both am and pm.

[anonymous-user]

outnumbered said:

We have a similar setup, highly insulated house, full UFH downstairs with a zone for each room.

Ours is programmed to go off overnight, as I don't see the point in keeping downstairs fully warm when there's nobody there. It comes on fairly early in the morning as it's not instantaneous heat. I'm sure it's cheaper to run it this way (by the same argument that it's cheaper to heat the hot water only when you need it).

You might find that you don't need to run the heating in all the rooms. We have one reception room which stays at 20-21C without needing to turn the UFH on at all, and we actually rely on the Plasma TV to heat the room up a little more if we're using it ! We also have a room that gets a lot of solar gain, and that one is set up so that the UFH doesn't try to do much until mid-morning, so if the sun's out, it then doesn't need to come on fully until late afternoon.

For the first time, I went into the Salus system (on the web page as it was easier than the app) and at around 12 noon today and I turned all the UFH and rads down to 18c, as they were at 22c.

It is now 6 hours later and the rooms are all still between 19.5c and 21.5c, and the boiler has been off since I made the adjustments at noon.

I also noticed that the front living room and front office room, reached 24c for most of the day with no input from the boiler, purely due to the solar gain.

This makes me think the house insulation is quite impressive as it doesn't seem to be losing much heat at all in several hours.

What time do you have your UFH come on in the mornings? What sort of a delay is there between the heat being turned on, and the floor beginning to warm the room?

[UTH]

You've probably got enough answers already, but my situation:

We ripped out all the ground floor radiators, now it's all UFH. 4 zones: Kitchen, Living room, Hallway, back study. At the moment the Living room and Kitchen is set to 17 overnight, then 6am-10pm 21 degrees. The other two zones are off. When it gets a bit colder we'll probably put the hallway on as well, same settings. Back study will remain off until we actually want to start using it (just keep the door shut at the moment)
Hot water goes on for an hour at about 2 in the morning, but we don't use much hot water at all (currently one electric shower, this will change soon though)

Upstairs is still radiators, we only use the main bedroom currently, so the thermostat for the upstairs lives in our bedroom, and is set to have that radiator come on for a couple of hours at 6am so our bedroom isn't freezing when we get up. The radiators in the 3 spare rooms are off at the valve.

As this will be our first full winter in this house with this heating setup, I imagine there's a bit of learning to do. I get the feeling when the temp drops to proper winter cold, I might need to have some things coming on earlier, because even now the living room isn't quite warm enough when I come downstairs at around 0830, so if it was in minus numbers overnight I reckon it'll be bloody cold, so might need the 21 temp to start earlier, but we'll see.

[18jcw]

We have been living in a new build house thats well insulated and gets quite a lot of solar gain for the past 8 years - open plan with largish atrium to first floor. Like you we have UFH on lower levels and radiators upstairs. We leave the heating on 24/7 and its set at 19.5 - when the sun comes in we have the back door and windows open plus our bedroom windows are open pretty much permanently. The upstairs radiators have never kicked in - in fact I have to crank the upstairs thermostat open every now and then get some fresh water to flow through the upstairs system.

The builder and architect were both adamant that its better to keep the thermal mass of the house 'topped up' by 24/7 small applications of heat rather than regular cooling down and rewarming. it seems to have worked well for us - only dissapointment was we paid up for a fancy gas fire thats never been switched on as there is absolutely no need for extra heat!

[AC43]

Pinkie15 said:

UFH is designed to be set to a temp and left at that; it runs at a lower water temp than rads; something like 40 deg cf rads at 80 odd degs.

We have UFH in our kitchen/diner, @80 sq m in 2 zones. We run ours at an indicated 22.5 deg (dial rather than digital thermostats). When set to just under 22 it feels like it’s off, at 23.5 it’s like a sauna. Depending on your floor type, we have ~75mm screed over ours, it takes a day or so to heat up. Conversely it takes a day or so to cool down. Apparently cos of the thermal mass of the screed (it’s like a giant storage heater). It’s not ‘agile’ to rapid changes in room temp like rads.

We too have closed/pressurised hot water system, just do a morning and evening heat cycle for about 1.5 hrs each time.

This is more or less what we've done and correct advice for UFH. And also, approximately what we also do for hot water.

For the rads upstairs it's more traditional; heat cycle in the morning & evening, off at night. Off or lower temp during the day. Even though rads cope much better in sudden temp fluctuations, you also don't want to cause particularly bad cold spots as that can have knock on effects on other parts of the system.

Once it's all set up and calibrated, of course, my better half flings windows and veluxes open all over the place and leaves them like that for hours but that's another story.......

[outnumbered]

Lord Marylebone said:

For the first time, I went into the Salus system (on the web page as it was easier than the app) and at around 12 noon today and I turned all the UFH and rads down to 18c, as they were at 22c.

It is now 6 hours later and the rooms are all still between 19.5c and 21.5c, and the boiler has been off since I made the adjustments at noon.

I also noticed that the front living room and front office room, reached 24c for most of the day with no input from the boiler, purely due to the solar gain.

This makes me think the house insulation is quite impressive as it doesn't seem to be losing much heat at all in several hours.

What time do you have your UFH come on in the mornings? What sort of a delay is there between the heat being turned on, and the floor beginning to warm the room?

I think the warm up time will be very system dependent so you'll have to experiment. I think in our biggest room it might take an hour for the temperature to go up by 1C.

[LocoBlade]

One thing I'd say is make sure the controls are designed for UFH with the ability to "learn" the room's characteristics so they adapt calling for heat to maintain a consistent temperature because if not it can be a right pain to control.

We had Hive in our old house controlling radiators and when we built a downstairs extension we installed wet UFH in the screed and added an additional zone controlled by a second Hive thermostat. The problem is Hive doesn't learn and adapt to a room's heating/cooling characteristics so if you set it to 20c it will keep calling for heat until it detects 20c in the room before switching off the boiler, by which time with in screed UFH you've often added a shed load of stored heat in the floor that continues to be released into the room causing a massive temperature overshoot of 2-3c sometimes, then on the way back down it will only call for heat when the temperature drops below 20c which is far too late for the floor to react and start emitting heat again for a few hours, so you get a massive undershoot as well. In the end I had to program the controller completely the opposite way to how you'd normally do UFH and set up multiple short bursts of higher temperature timeslots throughout the day so it would never over/undershoot too far.

UTH said:

You've probably got enough answers already, but my situation:

Yours and the UFH we've fitted in our new house is retrofit on top of the floor though, so can be controlled more like radiators as the floor surface heats up/cools down a lot quicker than in screed UFH like OP has. We've not got that big storage heater in the floor so possibly not quite as efficient at holding heat in the house but do have the advantage of being able to react more quickly to room temperature demand and use things like occupancy sensing to turn rooms on/off if the controls support it. I've got our study and living room set on occupancy sensing mode for most of the day (with Genuishub controls) so it defaults to 18c if nobody is in the room but increases to 20c if significant movement is detected for more than 5 minutes. For us that works quite well as we tend to be in the kitchen/family area during the day then go in the living room in the evening, but do occasionally spend more time in the living room which would be detected and the room will be heating up within 20-30 minutes

Edited by LocoBlade on Wednesday 6th October 19:03

[UTH]

LocoBlade said:

Yours and the UFH we've fitted in our new house is retrofit on top of the floor though, so can be controlled more like radiators as the floor surface heats up/cools down a lot quicker than in screed UFH like OP has. We've not got that big storage heater in the floor so possibly not quite as efficient at holding heat in the house but do have the advantage of being able to react more quickly to room temperature demand and use things like occupancy sensing to turn rooms on/off if the controls support it. I've got our study and living room set on occupancy sensing mode for most of the day (with Genuishub controls) so it defaults to 18c if nobody is in the room but increases to 20c if significant movement is detected for more than 5 minutes. For us that works quite well as we tend to be in the kitchen/family area during the day then go in the living room in the evening, but do occasionally spend more time in the living room which would be detected and the room will be heating up within 20-30 minutes

Edited by LocoBlade on Wednesday 6th October 19:03

Hmmmm yes this is a good point, it does seem to heat up pretty quickly. I am a bit nervous about when it gets really cold this winter though, I'm not 100% convinced it's going to keep the place as warm as originally hoped, but of course our insulation is on the to do list so that must make a difference.

[paulrockliffe]

Pinkie15 said:

Re the hot water; should have said that we’re a house of 5 (me, missus, 3 teenage daughters).

I go for the 1.5 hr spread as it allows for various showering regimes both am and pm.

There's a massive thread on this from not that long ago, maybe two. The systems are designed to be left on all the time, if you take heat out of the tank the boiler kicks in and puts it back, if you don't the heat loss is so low that aiming to save money by letting the tank go cool when you don't think you need hot water just isn't making a meaningful difference.

Your mindset is about anticipating use and heating in advance, but the system is intended to be used the other way around; you have stored capacity to allow you to heat after use.

In practice it usually makes no practical difference either way, if you shower in the morning, you'll have enough heat in the tank during the day whether you heat it again or not, and you're going to heat the tank anyway before you use it again. So chances are no matter how you set it the boiler won't kick in during the day whether it's off or not, but you do lose the flexibility to do daft stuff like dump all your hot water into the kids paddling pool without having to remember to manually charge the tank again.

Mine is set to heat all the time, apart from over night because I don't want the boiler to kick in and disturb me over night and it heats from half an hour before the heating comes on in the morning so there's no risk of heat being diverted away from the radiators.

I think the on all the time approach is probably slightly better as it should move some heating away from your morning/evening heating demand and give you either better response or lower risk of cold showers depending on whether your system is wired for heating or hot water priority.

But like I said, in practice the differences are probably minor to non-existent in practice.

[MrHappy]

LocoBlade said:

One thing I'd say is make sure the controls are designed for UFH with the ability to "learn" the room's characteristics so they adapt calling for heat to maintain a consistent temperature because if not it can be a right pain to control.

We had Hive in our old house controlling radiators and when we built a downstairs extension we installed wet UFH in the screed and added an additional zone controlled by a second Hive thermostat. The problem is Hive doesn't learn and adapt to a room's heating/cooling characteristics so if you set it to 20c it will keep calling for heat until it detects 20c in the room before switching off the boiler, by which time with in screed UFH you've often added a shed load of stored heat in the floor that continues to be released into the room causing a massive temperature overshoot of 2-3c sometimes, then on the way back down it will only call for heat when the temperature drops below 20c which is far too late for the floor to react and start emitting heat again for a few hours, so you get a massive undershoot as well. In the end I had to program the controller completely the opposite way to how you'd normally do UFH and set up multiple short bursts of higher temperature timeslots throughout the day so it would never over/undershoot too far.

UTH said:

You've probably got enough answers already, but my situation:

Have you considered turning down the temperature at the manifold by a few degrees? This may smooth out the peaks and troughs you’re experiencing.