What do people have their thermostats set at?

[Pete]

Been quite a bit if talk about thermostats and temp just recently and got me thinking what do people have their house temp set at? I used to do some work for a lady that had her house set at 27c and I used to perspire profusely. A young couple rent a house of us and they have it set at 25c. We have our house set at 19c and will prob be happy with 20/21 when we move into our new house. 

[Jeremy Harris]

Ours is set at 20.5 deg C, and that seems fine.  In practice the house sits between 20 deg C and about 21 deg C most of the time. 

[newhome]

Downstairs in the evening 20c. It then switches off and doesn't come back on unless it drops to 16c which doesn't happen as it only drops a max of < 2 degrees until the following evening at current temperatures so the lowest it drops to is circa 18.5c currently. I have the bedroom at 17c, again only in the evening and it switches off overnight. It's still 16.5c when I get up in the morning generally and back up to 17c when I go to bed. I don't have a constant temperature here throughout the day as I'm either not here or doing 'stuff' during the day so don't need it back on again until the evening. I have all of the rooms that I don't use switched off (on frost setting of 10c). Went into the lounge earlier to get something. I don't use that whole side of the house at all so nothing is heated over there and it was 11.5c, bloody baltic lol. Just across the hall the rooms I use are toasty warm at 20c. I'm glad I have lots of zones as it would be mental to heat all of the rooms here when I don't set foot in 2 thirds of them. I'm on an electric system so have to be mindful about the cost. Using it the way I do keeps the bills reasonable. 

[ProDave]

20 degrees here.  Heating goes off at night, but that is just because I want the house to be silent without the UFH circulating pumps running (the nosiest bit of our heating system) It does not cool down a lot over night.

 

We are getting into a routine where a couple of times a week we "indulge" and fire up the WBS, it's currently 25 degrees downstairs (the stove has gone out now) . I would never pay to heat it that hot, but wood is free.  It will probably be late tomorrow before the UFH comes on again so a burst from the stove will save some electricity.

 

Temperature is a funny thing.  I have worked in air conditioned offices fixed at 20 degrees, and you can sometimes feel cold and even with a pullover on feel cold, other times you were rolling up your sleeves and loosening your tie you were so hot.

[Ed Davies]

My preference when sitting still is anywhere between 21 and 23 °C. That's wearing a thickish sweatshirt and a pullover.

 

I keep to that in the spare bedroom which I'm now using as a study, the rest of the house is at various cooler levels though the bathroom's about the same. The kitchen is usually a bit less than 18 °C which if fine for cooking and eating. Bedroom surfaces are various temperatures from about 14 to 17°C. I don't use the main living room except for storage, and only have one of the two radiators in there turned on, which makes temperature control awkward as the main thermostat is in there.

 

I'm doing a little experiment to compare running the heating on a timed cycle vs running it continuously (just letting the thermostat do its thing). Mostly I've had it timed to run from 07:00 to 23:00 then switch it off manually when I go out but with it set to switch itself on again late afternoon. Did a week of continuous the week before last and this afternoon set the programmer to do it again for this week.

 

Comparing just that one week of continuous with the rest of November so far there's no obvious difference. It'll need comparing against the weather, of course. Quick plots showed little correlation with outside temperature but a bit more with wind. I'll need at least a few more week's of data and some thinking about how to deal with “windchill”.

 

[daiking]

18

 

you soft ********

[newhome]

2 hours ago, Ed Davies said:

Comparing just that one week of continuous with the rest of November so far there's no obvious difference.

 

What do you use for heating? Tank or direct to UFH? My worry about running it continuously is that the boiler will continually top up the 475l TS to keep it at temperature if the UFH continually calls for heat in order to keep the temperature constant. My theory is that I don't need it so hot during the day so it can just boost it to 20 downstairs in the evening and then that's enough to keep the house at an OK temperature until the following evening. 23 degrees would be roasting IMO! It got to 24c in the summer and during the hottest weather and that was way too hot for me. 

[Temp]

Our varies by room but typically 20 first thing, 18 during the day, 20 in evening, 16-18 depending on the room at night.

 

Room stats and tank stats have hysteresis so boiler certainly doesn't run continuously. 

[Ed Davies]

9 hours ago, newhome said:

What do you use for heating?

 

This is for the house I'm renting during the build, not what I'd choose for myself. It's an oil boiler direct to radiators. DHW is from a conventional vented cylinder. My landlord had the oil boiler replaced in the summer and the system was converted then to S-plan: two zone valves, one for the CH and one for the DHW indirect coil.

 

The programmer is set to heat the DHW cylinder for an hour or so in the late afternoon and generally does so in half an hour. That gives plenty of hot water for the washing up in the evening and general washing evening and morning. The shower is electric (presumably to get mains pressure) so, except for the occasional bath, there's always more than enough hot water.

 

Graph of relevant data for Friday and Saturday attached. Room temperature (red) on the left hand scale. All other variables on the right hand one (arbitrarily labelled humidity). Humidity is percent RH, power (pale blue/cyan) is in hundreds of watts (so the two big spikes just before the midnights are my showers, 7 kW electric shower). Boiler state is derived from the temperature of the radiator (so doesn't include DHW heating). It it were my house I'd add a couple of relays hung off the wiring centre to monitor the calls for heat by the CH and DHW tank but don't want to mess with my landlord's wiring.

 

The blibs of power overnight and while I'm out are the fridge running. Sometimes the power monitor picks up the start current spike from that.

 

When the heating is stabilised the boiler just runs for 15 minutes or so in each hour to a fairly regular pattern, controlled by the living room thermostat. When it's cold and windy the runs get closer together. When I've left the heating off while I'm out or overnight it initially runs continuously for 20 minutes then, once the circulating water is all up to temperature, short cycles for a while till the living room thermostat stops calling for heat.

 

What's not obvious from just eyeballing the graph is how much is actually saved by letting the house cool down overnight and while I'm out then heating it back up. Just looking at the graph it seems like it's a bit of a wash hence my attempts to measure more accurately. Intuitively, any time the house is cooler it should be losing heat more slowly so the net amount of heating should be less but I speculate that there are other factors which mean there's less difference than you might expect.

 

 

[jack]

13 hours ago, Ed Davies said:

Bedroom surfaces are various temperatures from about 14 to 17°C. I don't use the main living room except for storage, and only have one of the two radiators in there turned on, which makes temperature control awkward as the main thermostat is in there.

 

Our entire house temperature dropped to 14.5°C while we were away for three weeks last Christmas and left everything (and I mean everything) off. We found that seriously cold on our return.

 

It wasn't helped by the fact our ASHP had packed up a few weeks before, and we only had a 1500W column heater to warm the house back up. Took several days to get back up to operating temp but we got there in the end. 

 

We don't actually run a thermostat at the moment, but the dynamics of our heating system means that the slab seems to reach about 22°C before the ASHP stops providing heat (presumably because the return temp gets too high). Bedrooms are naturally 1-2° cooler due to not having any heating. Bathrooms are similar, but we're about to install IR panels to take the chill off the tiles in the morning. 

[Ed Davies]

35 minutes ago, jack said:

Our entire house temperature dropped to 14.5°C

 

My bedroom temperature drops more than that overnight without the heating on and is clearly on the way further down when the heating comes on in the morning, but then even a well-built Victorian or Edwardian (not sure) house is not likely to compare well against a modern one.

 

More interestingly, any idea if your house had stabilised at that temperature or was still cooling? I'm guessing that any bright days would have kept it at something not far below that temperature just by solar gain alone.

[jack]

I didn't keep that close an eye on the weather, but I believe it was very cold and windy without much sun while I was away. We're a little light on solar gain due to trees and our window layout, so our house tends to be cooler on average than some other MBC builds (eg, Jeremy needs less heating, but more cooling, than us).

 

Unfortunately my 1-wire system was on the blink during that period so I can't tell exactly what was happening. I can't imagine it would have fallen too much further after 3 weeks with no internal gains at all (other than energy losses from the fridge and minor electrics).

[Stones]

I've got our master controller/thermostat set to 21C.  Most of the house sits at 21.5C, our bedroom slightly less, due I think to the increased level of ventilation to that room.

[joe90]

After finally getting the ASHP working my wife asked how to control the heating, I showed her the room stat in the hallway. After she went to work I looked and it was racked up to 23’. Bugger, I should have made it a “false” controller.?

[newhome]

3 hours ago, Ed Davies said:

When the heating is stabilised the boiler just runs for 15 minutes or so in each hour to a fairly regular pattern,

 

If that happened here I would use 6kw every hour.  I don’t think it would as the room temps don’t drop that much, if at all, in an hour. When the boiler fires once a day it takes an hour to an hour and a half to reach the temp that the cylinder stats are set to, so that’s between 24 and 36kw. I can’t see it being less than that (or the same) if the heating is set to be a constant temperature. May have to try it over a few days and check however I don’t have a snazzy way of monitoring it so it will be rough and ready from meter readings (heating / DHW is on a different meter so I can work that out ok at least). 

[TerryE]

To answer @Pete's Q we set ours at 22.8 °C.  We originally used 21°C as discussed by Jeremy et al, but found that we needed to put light sweaters on in the evening when sitting quietly.  The extra hike means that we can dress indoors for summer T shirt weather all year round.  We find we prefer this, but as I've mentioned on other posts, we spend a lot of time on one of the Greek islands so have got used to the warmer temperatures.  It's all a matter of personal preference -- or friction if you live as a couple and one partner prefers it a degree or two warmer than the other.

 

3 hours ago, jack said:

Our entire house temperature dropped to 14.5°C while we were away for three weeks last Christmas and left everything (and I mean everything) off. We found that seriously cold on our return.

 

The thermal capacity of the internal fabric -- all of the plasterboard et al -- is non-trivial; about the same as the slab IIRC.  The time constants of the house as a system is many days.  Because our only source of heat is the groundfloor slab, our 1st floor is about 1°C cooler than the ground floor, but apart from that offset, pretty much everything -- walls, floors, all the internal fabric -- stabilises at the same temperature.  If we put too much or too little heat in, then the air temperature might vary be ½°C or so, but because all of the fabric is at this steady temp, then the house will rapidly recentre at this set point.  Changing the set-point is hard work -- for example when we stepped  from 21 - 22.8 °C it took 2-3 days for the house to settled down again.  So I would guess that it would take quite a lot of heat input and 7-10 days to lift a passive house by 6°C or so and restabilise.   Do the maths.  Let us say that you dropped the house by an average of 3°C over 24 days then for our house this would save us about 60kWh heat or 20 kẂh electricity if using an ASHP.   @jack, you've also got and MBC slab and frame so the numbers will be similar for you.   Is all of the hassle of living in an icebox for 3 or so days worth saving a couple of £s in electricity charges?   

[jack]

9 minutes ago, TerryE said:

@jack, you've also got and MBC slab and frame so the numbers will be similar for you.   Is all of the hassle of living in an icebox for 3 or so days worth saving a couple of £s in electricity charges?   

 

Why do you conclude that this decision was about money?

 

We turned off the heating before we went away because our ASHP was on the blink and we didn't to leave a resistive heat source unattended for three weeks in case something went wrong. 

[HerbJ]

We have the downstairs as one zone and this is set to 21 °C.it maintained within 0.5 °C  24 hours/day. We tried 22 °C for a few days but decided 21 °C was comfortable temperature, as when we are both the kitchen,/family room  or lounge for a few hours the temperature rises quite quickly anyway.

 

The 1st Floor bedrooms and bathrooms have individually UFH controlled zones.Normally, there are only two of us at home and we have the master bed and ensuite at 22 °C ( keeps my wife happy)and the rest of the settles at 19+ °C, without the UFH being activated. If we have visitors, we can adjust bedrooms to suit their comfort levels.

 

We are currently away in Spain. I have set the downstairs at 18.5 °C  and the upstairs is set at 17 °C but hasn't been necessary as the upstairs has settled above that though we don't have the MVHR on except for a daily 30 minute ventilation cycle.

[newhome]

21 minutes ago, TerryE said:

Is all of the hassle of living in an icebox for 3 or so days worth saving a couple of £s in electricity charges?   

 

Nope! Having experienced it taking several days to bring my heating up to 20 degrees when I was away last Christmas it’s definitely not. The heating wasn’t working properly then so I had no choice but I hope to set the controller so that the heating comes on 24 hours before I am due to return this year. Will be luxury if it works lol. 

 

What determines how low a house’s temperature will drop to with no heating on? In the side of the house that I don’t use the temperatures both upstairs and down are just over 11 degrees. The heating is off in those rooms but the frost setting is set to 10 so they won’t drop below that. The bedroom that is not heated behind mine is the same temperature as mine but I imagine that’s because it’s above the room where the TS is and the hot pipes go up into a cupboard in that room (I think!). The rooms that are not heated between the cold side of the house and the warm side are somewhere between the 2. I seem to recall that the temperature in here has been in single figures before however ... ❄️❄️❄️

 

 

[TerryE]

4 hours ago, Ed Davies said:

What's not obvious from just eyeballing the graph is how much is actually saved by letting the house cool down overnight and while I'm out then heating it back up. Just looking at the graph it seems like it's a bit of a wash hence my attempts to measure more accurately. Intuitively, any time the house is cooler it should be losing heat more slowly so the net amount of heating should be less but I speculate that there are other factors which mean there's less difference than you might expect.

 

It seems to me that there are two broad thermal management approaches:

• Thermos flask, that is you have a very low U-value external boundary and minimise other heat losses, but within this outer boundary any heat barriers are an order of magnitude+ lower than the external barrier.  In this scenario it makes sense to keep the whole internal environment at the same time-constant set point and accept the heatflow at the barrier.  That's in reality what people like Jeremy, Jason, and I do.  Energy costs are very small because of the efficiency of the external barrier, and because there aren't material internal barrier you can use a single heat source like groundfloor UFH , so the whole heating system is so much simpler -- we have no rads; no upper floor UFH or the like with all of the entailed costs and complexity.
• Onion ring / many layers.  This is opposite to the thermos flask approach: only heat the living space that you use and when you use it to the comfortable temperature, so the snug might be at 21°C for 7 hrs a day, the other lived-in rooms at 19°C for 12 hrs a day, the whole house at 14°C etc.  This is a sort of defence-in-depth approach to heat losses.  

@Ed Davies, in your case you seem to be running the living room at an average of around 18½-19°C by ToD heating rather than a target of 21°C .  The rest of the house probably has similar but stepped down figures.  so the first order would be to plug a ΔT of 2½ °C into your houses U-value calcs for see what the energy implications would be.

 

 

22 minutes ago, newhome said:

What determines how low a house’s temperature will drop to with no heating on? In the side of the house that I don’t use the temperatures both upstairs and down are just over 11 degrees.

 

Karen, in practice you seem to be using your house as 2×Semis with one effectively unheated.  There will be an internal wall interface between the two halves, and an internal stud wall with PBoard either side and acoustic insulation will have a U-value of roughly  1 W/m²K and the heat flowing from the warm to the cold side at a  ΔT of 10°C will be 10X W where X is the area of the internal partition interface.  So this internal wall is like a huge radiator sucking heat out of the warm half and heating the cold half.  The cold half will be in rough equilibrium with external wall losses matched by the input from the warm side.  Keeping half the house warm will save around maybe 25% or less of the heating bill rather than the 50% that you might expect -- still this is still a non-trivial amount.  

 

36 minutes ago, jack said:

Why do you conclude that this decision was about money? 

 

TBH, J in your case I didn't think that it was about money, but we've now dismissed this.  As far as monitoring our HA I use a combination of the Node RED node-email to push alarms which I pick up anywhere using my phone, and OpenVPN which is simple to use and is brilliant for doing remote access / monitoring.  I run the server install on an RPi which opens a (non-standard) port onto the internet for SSL connection, and so I can securely access my HA and other services / servers in the house from anywhere -- and I can also watch iPlayer from a Greek Taverna.

[newhome]

9 minutes ago, TerryE said:

Keeping half the house warm will save around maybe 25% or less of the heating bill rather than the 50% that you might expect -- still this is still a non-trivial amount.  

 

I didn’t expect it to save 50% but you’re right a 25% saving is not insignificant on an all electric system. There is MVHR here but I’ve no real clue as to how that’s set up TBH plus I can’t actually get to it currently (another job on the to do list!). 

 

And yes I do use it like 2 semis! I literally only use that side of the house if I have visitors. That’s the consequence of having a house that’s way too large for just me. It does however give me food for thought for when I move house ?

 

 

[TerryE]

6 minutes ago, newhome said:

There is MVHR here but I’ve no real clue as to how that’s set up TBH plus I can’t actually get to it currently (another job on the to do list!). 

 

Karen, I realise that this is always a Q of priorities, but I would keep a close eye on the humidity in the unheated half if you aren't running the MVHR (you can buy cheap LCD thermo + humidity readout sensors for around £10).  You don't want to let it get up to condensing levels, as this will encourage mould and mildew in the unheated half which will be a PITA when you want to sell and move.  Commissioning the MVHR would be one way of mitigating this.

Edited November 26, 2018 by TerryE

[Ed Davies]

Wot @TerryE just sed: if one room's at 21 °C and 50% relative humidity and another room is at 11 °C then any air that filters through from the warm room to the cool room will just about reach its condensation level. Rough rule of thumb: the equilibrium vapour pressure doubles (halves) for each 10 °C increase (decrease) in temperature.

[Ed Davies]

1 hour ago, TerryE said:

so the first order would be to plug a ΔT of 2½ °C into your houses U-value calcs for see what the energy implications would be.

 

? It's a rental house which I really hope this is my last winter in it. I've had a quick scan through the EPC and I'm sure the estate office would let me have a copy if I asked but I doubt the assessor had any better idea of the insulation and actual U-values that I have (i.e,, very little). I'm doing monitoring for short-term comfort at minimum cost (oil burn) and to have tools to hand for tuning when I move into the house I'm building.