It’s freezing… how often do you turn your heating on?

[Janela]

It's amazing how different a temperature feels. I walk into the kitchen and think it's rather warm (I spend most of the day outside busy with horses)
my husband comes in from his office and thinks it's freezing!

 

[Mrs McG]

I keep my thermostat on at 16 night and day but I sometimes increase it to 18 in the early morning and evening if I’m having a particularly slothful day. Heat retention is definitely better since I replaced my windows but the cottage will never be great at holding in heat.

 

[mardinor]

We keep the heating on all day at 18C and at night programmed to 16C. Two-foot thick stone walls, plus cast iron rads, even out the heat meaning on/off control not worth it and the uninsulated loft does a great job of cooling the upper floor bedrooms by a couple of degrees so it's nice to sleep!
Much prefer to live in a colder house with fresh air than a stuffy warm box. Can't sleep in the latter.

 

[Lacan07]

Its amazing how 18c has become the 'new norm'. The house I grew up in during the 70s / 80s barely dropped below 20-21c. I guess there's a multitude of reasons why but lets not get into that.

15c is fine at night when tucked up in bed (or as low as you're prepared to let the house go) but not for daytime activities imo.

 

[paulc]

Can you explain about the low flow temperature bit I am not aware of this and we have very few radiators.

With a condensing boiler, efficiency rises when the flow (more precisely, the return) temperature is below ~54°C. The lower the temperature, the better the efficiency (see graph below).
However, the output of a radiator is a function of water temperature - The higher the temperature, the more heat radiated. Dropping the flow temperature from 70°C down to 50°C effectively reduces radiator output by half. So if you are currently struggling to heat your home, you don't really want to be reducing the flow temperature. The only reason I can get away with running at 60°C or lower is because my radiators are a lot bigger than really needed.
As always, there is a but - Most gas boilers will start to become more inefficient if you try and push the flow temperature down too low. 45°C is about the limit for me. If I try and go to 40°C, gas consumption increases with no extra heat being generated (have a sensor attached that records the amount of energy going in to the heating system).

 

[DaveG]

In relation to some of the earlier comments on how low a temp is healthy for an old building I came across this resource this morning.

https://www.gov.wales/sites/default/files/publications/2024-01/factsheet-3a-considering-summertime-relative-humidity-in-older-properties.pdf

14c minimum was recommended. Thought it may be of interest here.

 

[fernicarry]

Just got a bill for 280 from Octopus. Estimated but if correct not as bad as I was expecting.

Each room here is a separate zone with its own programmable thermostat (Heatmiser). Unused rooms are set to between 12 and 14. The higher the temperature difference to outside the faster you lose heat so you want to stay as low as you can without going below the dew point when not occupied. But the lower it goes the longer the recovery time back to a comfortable temperature of course.

At least its set to get warmer from tomorrow. The first few days of below freezing the internal temps here held up surprisingly well but its taking longer and longer each evening to get past the magic 18' as the building fabric cools down. Will be calling on boiler #3 (wood burner) tonight methinks.

Apparently the country's gas reserves are lower for the time of year than normal due to an early start to the heating season. And the electricity market was a bit tight during the week due to the still wind conditions. Govt response pointed to our "robust and diverse energy market". That seems to be gas to generate electricity when the wind doesn't blow (cold spells like this often accompanied by dead calm) and gas to heat our homes. Different use of the word "diverse" to what I'm used to...

 

[philpjuk100]

I light two log burners when rising and burning mainly logs (hardwood, dry £250 for two builders bags) soon have the downstairs to 25c+. I know that is far too hot but I am "poorly" Most visitors comment on the temperature but both I and Frodo the cat are happy. I live downstream from Staythorpe gas fired power station which seems to have been working "flat out" for nearly a week but the Large Mansfield wind farm is stationary.

 

[lizziecupcakes]

hi all, thanks so much for your responses and sharing! It's really interesting about the temperature people feel comfortable in. Thanks @DaveG for the link and wow - £14 per day during this cold snap is a lot - do you have a large house? I read from World Health Organisation that the recommended internal temperature is 18 degrees for human and house health. I personally find 18 degrees a bit too warm. My other annoying issue is that the heat rises so my upstairs is a lot warmer than my downstairs.

Agree with the comment that the past couple of days reaching 18 degrees has been taking longer and when it does reach it, it disappears pretty quickly, so I've just left it at 15 degrees on the thermostat which feels cosy enough with all my insulating clothing I am wearing. Even right now, it's 15 degrees downstairs but 18degrees in the bedroom!! Thats 3 degrees difference! It's funny because we wanted to be in this house for a winter or two without too much reno work done so we can see what's needed/not needed and this happens to be the coldest winter for 15 years!! So at least I kinda know what to act on in prep for the next winter (fingers crossed!)

Also, some people mentioned radiators. I have large radiators on the ground floor, and smaller ones upstairs (all came with the house). They are panel convector heaters.

I'm thinking about getting cast iron heaters in the near future because I read that they retain heat for longer periods after the boiler shuts off due to their high thermal mass. And they're great for maintaining warmth in continuously used spaces. My plumber suggested panel convector heaters are better though - apparently they heat the room more and circulate it through the room better, which cast iron heaters will heat the wall behind it and a lot of heat is lost there in that spot. I'm not sure about that though.

I can't wait for this freezing snap to be over!

Also, I live in SW London. For those with log burners, where do you get your logs from?

 

[fernicarry]

cast iron heaters will heat the wall behind it and a lot of heat is lost there

He may have a point. Since they warm up and stay warm they do actually transfer some heat by radiating whereas panel radiators transfer majority of their heat by convection. The radiation will go in all directions including towards the wall but heating up the fabric is no bad thing. Heating by convection can be very uncomfortable, the hot air rises directly above the radiator, rolls along the ceiling, cools down and then sinks to the floor. So what your toes feel at floor level is the coldest air in the room. If you ever climb a step ladder when the heating is on you'll be hit by how much hotter it is at ceiling level.

One of my earliest upgrades was to replace the single steel panel radiator in the living room with two last cast iron rads. One under the window, something else heating "engineers" will tell you not to do, another "rule" being always always put radiators on an internal wall to minimise heat loss. Remember the convection effect where cooling air sinks down, that's even worse in front of a window because the air cools even faster, but with a radiator under the window you get a column of rising hot air to counter that effect. You may well lose more heat as a result but the first goal is to feel comfortable. With the old radiator the living room simply didn't heat up now it can be perfectly comfortable.

Word of warning, don't buy the cheapest cast iron rads you can find on the internet like I did. They're assembled from rubbish foreign castings that don't go together particularly well. I've had quite a few weeping joints between sections and the paint has peeled off around many of the joints due to the gaskets sticking out. It took three of us to carry them in so they're probably not going anywhere now. I'll just have to tart them up as best I can. I've found a place that builds reclaimed Ideal Standard radiators to order that I intend to use for the rest of the downstairs rooms.

 

[paulc]

One of my earliest upgrades was to replace the single steel panel radiator in the living room with two last cast iron rads. One under the window, something else heating "engineers" will tell you not to do, another "rule" being always always put radiators on an internal wall to minimise heat loss.

Thought it was fairly standard practice to put radiators under a window to counter the sinking cold air coming off the glass. But with decent double/triple glazed windows, an internal wall is my preferred option.

 

[CliffordPope]

I've often noticed a quirk in my temperature appreciation. I find radiant heat direct from source much hotter than background heat. So quoting the air temperature is meaningless for me. I love being toasted by a blazing fire, even though the air temperature might be freezing. In contrast hot air, as from underfloor heating, is merely stuffy, never actually warming, however hot.
Cats seem to work in the same way. Ours will lie inches from a fire risking their fur singeing, but don't mind sleeping in a bedroom with ice on the windows.

 

[Flyfisher]

I'm thinking about getting cast iron heaters in the near future because I read that they retain heat for longer periods after the boiler shuts off due to their high thermal mass. And they're great for maintaining warmth in continuously used spaces. My plumber suggested panel convector heaters are better though - apparently they heat the room more and circulate it through the room better, which cast iron heaters will heat the wall behind it and a lot of heat is lost there in that spot. I'm not sure about that though.

It's true that the (usually) higher thermal mass of cast iron radiators retain heat for longer than standard radiators after the boiler shuts off, but the consequence is that they also take longer to warm up after the boiler is switched on. Sadly, it's not that easy to avoid the laws of physics. The boiler can only generate a certain amount of heat and the aim is to 'lose' that heat into the desired room(s). There are various ways of 'losing' that heat into a room, e.g. light steel radiators, heavy cast iron radiators, underfloor pipes that heat the floor, etc and each method will 'lose' that heat into the room at different rates over different times, but there is no method that I know of that can 'lose' more heat into the room than the boiler can provide. All that each method can do is to take more or less time to heat up and cool down.

 

[DaveG]

It's true that the (usually) higher thermal mass of cast iron radiators retain heat for longer than standard radiators after the boiler shuts off, but the consequence is that they also take longer to warm up after the boiler is switched on. Sadly, it's not that easy to avoid the laws of physics. The boiler can only generate a certain amount of heat and the aim is to 'lose' that heat into the desired room(s). There are various ways of 'losing' that heat into a room, e.g. light steel radiators, heavy cast iron radiators, underfloor pipes that heat the floor, etc and each method will 'lose' that heat into the room at different rates over different times, but there is no method that I know of that can 'lose' more heat into the room than the boiler can provide. All that each method can do is to take more or less time to heat up and cool down.

100%.
Sometimes it’s about what the occupier finds most comfortable. For me, the added factor is about what’s best for the building. Everything I’ve read suggests large swings in temperature variation is a bad thing in an old solid walled building. Items that get hot very quickly but also cool very quickly create these larger variations.
Back in my last house, when I first had my underfloor heating I loved the feel of a really warm floor on my feet but I soon realised that this would spike air temp meaning the floor switched off, you had warm air but cold floor. No good. The art was to get the lowest flow temp possible to keep the floor at room temperature level. Not hot, not cold. Appreciate that’s not for everyone where you feel neither hot, nor cold but it is super efficient and in our older buildings helps with moisture management.
For now I’ve purchased a single iron rad, over sized but with the hope it will more or less be at a constant temperature throughout the day. Completely experimental but will help me decide if it’s worth installing these in other rooms.
The fact that I think they look fantastic is a bonus!

 

[Lacan07]

Thought it was fairly standard practice to put radiators under a window to counter the sinking cold air coming off the glass. But with decent double/triple glazed windows, an internal wall is my preferred option.

I thought siting rads on an internal wall was a no, no?

 

[lizziecupcakes]

I thought siting rads on an internal wall was a no, no?

I thought this too. I thought rads had to be under a window too because.. science? but maybe it's not really needed if you have double glazing

 

[DaveG]

It’s a bit of a long running argument. Traditionally always under a window for the reasons mentioned but if heat loss on the window wall is minimal due to modern insulation, A+++ double glazing then the argument is it can go anywhere. Usually wherever allows you to make the most of room layout/furniture placement.
I think if you’ve an old house the original argument still stands up

 

[Cubist]

I thought this too. I thought rads had to be under a window too because.. science? but maybe it's not really needed if you have double glazing

The largest cold surfaces in most rooms are the windows, siting radiators under these stimulates and accelerates the air convection currents in the room to heat that room more effectively. Placement of radiators elsewhere other than near a window merely reduces the speed at which the room can reach an ambient temperature while drawing colder air from more distant sources.

 

[a twig]

I always put radiators on external walls in the hope it will mitigate the damp problems

 

[overlander matt]

Interesting thread on the heating costs etc. We heat to 15deg throughout the house and then 17deg at certain times of day on specific days of the week, we have around 12 different zones with a thermostat. I'm accused of breaking all manner of human rights conventions. There are a couple of log burners that are very welcome and one contributes a little extra heat in the form of a back boiler. In 2024 our energy costs were in the order of £2600. I didn't think this was too bad for the size of the house and higher cost of energy than in previous years. A bit colder than we would like but ok... 2025 has been a cold start with yesterday breaking the £30 daily barrier (gas and electricity) for the first time.

I've noticed recently through the use of smaller humidistats around the house that the temperatures are around 2deg lower than the room thermostats. Has anyone else noticed such variations?