Warming a house all day

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sTeamTraen
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Warming a house all day

Post by sTeamTraen » Tue Jan 05, 2021 7:56 pm

It has been pointed out that lockdown will cost people money in terms of having to heat their house all day. I'm trying to work out how to put an estimate on the increase.

Let's say the baseline is a two-person household where in normal times the heating comes on at 0700, they get up at 0730, leave home for work at 0800 at which point the heating goes off. Then the heating comes on at 1800, they get home at 1830, heating goes off at 2300, and they go to bed at 2330. So the heating runs for 6 hours per day.

In the COVID situation the heating comes on at 0800 and stays on until 2300, so 15 hours per day.

What are the differences?

More energy is expended because: (a) duh, there's 15 versus 6 hours of heating; (b) the mean difference between inside and outside temperature is higher (say 15-20C if we assume thermostat set to 20 and outside temperature is +5 for 8 hours of daylight, 0 for 7 hours of darkness) and hence the loss through the walls/windows is higher because of the steeper temperature gradient.

Less energy expended because: (a) Not starting from a low internal temperature the second time (house maybe cools down to 10C by 1800), (b) two bodies are generating warmth, (c) maybe they cook at lunchtime, (d) computers and lights producing heat. The last three of those are probably marginal unless their exercise regime involves Chris Froome-style levels of energy expenditure on the exercise bike (and even then).

What else would need to go into a model of this? (Of course, compared with pre-COVID, there is the difference of commuting costs, which could be considerable. But then people are not furloughed at 100%, so it's probably best to ignore that for now and start another column.)
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Re: Warming a house all day

Post by Bird on a Fire » Tue Jan 05, 2021 8:05 pm

I reckon heating costs per hour of heating will rise as a non-linear function towards some asymptote (I bet the difference between 23 and 24 hours is minimal). Six continuous hours would be cheaper than two bouts of three, but I don't think fifteen would.

Outside temperature is also going to be important.

I'd be very surprised if body warmth from two people would make much difference to a thermostat, except perhaps in a very small, very well-insulated space (he wrote, with numb fingers, in his open-plan uninsulated apartment).

The answer is definitely "more energy expenditure", and you can probably ballpark it just by comparing 2 × 3 hours with 15 hours.
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Re: Warming a house all day

Post by discovolante » Tue Jan 05, 2021 8:27 pm

I reckon I'll just compare my bills.
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Re: Warming a house all day

Post by tenchboy » Tue Jan 05, 2021 8:32 pm

Decent base layer (thermal longs plus long sleeved top) turn the thermostat down 2,3 degrees; baggy trousers woolen socks plus thin top shirt and thin jumper, 2 or 3 degrees more; fur lined slippers and thick jumper and or quilted/padded jacket, same again.
Cold shower and a bowl of porridge with honey and sultanas first thing in the morning; sets you up for the day; f.ck the heating, who needs it?
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Re: Warming a house all day

Post by dyqik » Tue Jan 05, 2021 8:36 pm

The costs aren't going to be as big as they might be for a couple of reasons:

1) the middle of the day is the time with the lowest temperature difference.
2) there's some cost associated with letting the house cool off, and then recover temperature - the heat capacity of the house is significant.

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Re: Warming a house all day

Post by Woodchopper » Tue Jan 05, 2021 9:08 pm

dyqik wrote:
Tue Jan 05, 2021 8:36 pm
The costs aren't going to be as big as they might be for a couple of reasons:

1) the middle of the day is the time with the lowest temperature difference.
2) there's some cost associated with letting the house cool off, and then recover temperature - the heat capacity of the house is significant.
We had a long thread about this in the other place. Basic conclusion was that its complicated and the financial gain or loss is influenced by things like how well the house is insulated and the price energy at different times of the day. ETA and of course the outside temperature.

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Re: Warming a house all day

Post by dyqik » Tue Jan 05, 2021 9:24 pm

Woodchopper wrote:
Tue Jan 05, 2021 9:08 pm
dyqik wrote:
Tue Jan 05, 2021 8:36 pm
The costs aren't going to be as big as they might be for a couple of reasons:

1) the middle of the day is the time with the lowest temperature difference.
2) there's some cost associated with letting the house cool off, and then recover temperature - the heat capacity of the house is significant.
We had a long thread about this in the other place. Basic conclusion was that its complicated and the financial gain or loss is influenced by things like how well the house is insulated and the price energy at different times of the day. ETA and of course the outside temperature.
Solar gain during the day is also a big factor - south facing windows can pull in a lot of heat on the sunny day. My office, which isn't designed for this, gets to 30C in February when it's sunny and -15C outside.

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Re: Warming a house all day

Post by Brightonian » Tue Jan 05, 2021 9:42 pm

tenchboy wrote:
Tue Jan 05, 2021 8:32 pm
Decent base layer (thermal longs plus long sleeved top) turn the thermostat down 2,3 degrees; baggy trousers woolen socks plus thin top shirt and thin jumper, 2 or 3 degrees more; fur lined slippers and thick jumper and or quilted/padded jacket, same again.
Cold shower and a bowl of porridge with honey and sultanas first thing in the morning; sets you up for the day; f.ck the heating, who needs it?
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That's pretty much me, except I'm trying to keep the heating on (am having a slow passive-aggressive battle with another tenant who's trying to keep the heating off), and I didn't bother with a shower this morning (would've taken too long to remove all the layers of clothing).

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Re: Warming a house all day

Post by Woodchopper » Tue Jan 05, 2021 10:07 pm

dyqik wrote:
Tue Jan 05, 2021 9:24 pm
Woodchopper wrote:
Tue Jan 05, 2021 9:08 pm
dyqik wrote:
Tue Jan 05, 2021 8:36 pm
The costs aren't going to be as big as they might be for a couple of reasons:

1) the middle of the day is the time with the lowest temperature difference.
2) there's some cost associated with letting the house cool off, and then recover temperature - the heat capacity of the house is significant.
We had a long thread about this in the other place. Basic conclusion was that its complicated and the financial gain or loss is influenced by things like how well the house is insulated and the price energy at different times of the day. ETA and of course the outside temperature.
Solar gain during the day is also a big factor - south facing windows can pull in a lot of heat on the sunny day. My office, which isn't designed for this, gets to 30C in February when it's sunny and -15C outside.
Yes, that too.

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Re: Warming a house all day

Post by Fishnut » Tue Jan 05, 2021 10:31 pm

I've put the heating on all day (thermostat-controlled, 17C cut-off) as I was f.cking freezing (at one point I had snood, earmuffs, longjohns and a blanket on top of my normal clothes and was still cold) and the damp was getting really bad. It takes ages to heat the house (metre-thick stone walls) and we have damp everywhere that's been getting worse this winter. I've even got some appearing in my bedroom and that's on the 3rd floor! I bought an electric blanket today as the hot water bottle wasn't cutting it overnight.

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Re: Warming a house all day

Post by tenchboy » Tue Jan 05, 2021 10:40 pm

Fishnut wrote:
Tue Jan 05, 2021 10:31 pm
I've put the heating on all day (thermostat-controlled, 17C cut-off) as I was f.cking freezing (at one point I had snood, earmuffs, longjohns and a blanket on top of my normal clothes and was still cold) and the damp was getting really bad. It takes ages to heat the house (metre-thick stone walls) and we have damp everywhere that's been getting worse this winter. I've even got some appearing in my bedroom and that's on the 3rd floor! I bought an electric blanket today as the hot water bottle wasn't cutting it overnight.
Just in case you missed a trick: insulation below is as important as insulation above. In the winter I spread out a sleeping bag - inside up - underneath my under-sheet and then another sleeping bag - inside down - on top of my duvet. Get in that and roll up, means I only wear an oversized t-shirt in bed and I'm as snug as a bug in a toaster.

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Re: Warming a house all day

Post by Fishnut » Tue Jan 05, 2021 10:48 pm

tenchboy wrote:
Tue Jan 05, 2021 10:40 pm
Fishnut wrote:
Tue Jan 05, 2021 10:31 pm
I've put the heating on all day (thermostat-controlled, 17C cut-off) as I was f.cking freezing (at one point I had snood, earmuffs, longjohns and a blanket on top of my normal clothes and was still cold) and the damp was getting really bad. It takes ages to heat the house (metre-thick stone walls) and we have damp everywhere that's been getting worse this winter. I've even got some appearing in my bedroom and that's on the 3rd floor! I bought an electric blanket today as the hot water bottle wasn't cutting it overnight.
Just in case you missed a trick: insulation below is as important as insulation above. In the winter I spread out a sleeping bag - inside up - underneath my under-sheet and then another sleeping bag - inside down - on top of my duvet. Get in that and roll up, means I only wear an oversized t-shirt in bed and I'm as snug as a bug in a toaster.
Thanks :)

The bedroom just gets so damn cold - I don't have a thermometer but based on the temperature drop from the rest of the house when I turn the corner on the stairs I'd guess it's 14/15C. I can create nice little warm air pockets but I still get drafts coming in due to my annoying need to have my head outside the covers. Plus the dog sleeps on the bed and he gets cold so I figured the blanket would benefit us both!

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Re: Warming a house all day

Post by sTeamTraen » Tue Jan 05, 2021 11:08 pm

dyqik wrote:
Tue Jan 05, 2021 9:24 pm
Solar gain during the day is also a big factor - south facing windows can pull in a lot of heat on the sunny day. My office, which isn't designed for this, gets to 30C in February when it's sunny and -15C outside.
Here is my "office" (one end of the living room) window. It's 6m² and south-facing, so with the sun on it I reckon I'm getting 500W at least.

The really cool thing is that for the 40 warmest weeks of the year the sun is above the level of the upstairs flat's balcony. So I only get that heat in winter, when I need it. It's the same effect as the rather marvellous heliodome.

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Re: Warming a house all day

Post by nekomatic » Wed Jan 06, 2021 12:37 am

Fishnut wrote:
Tue Jan 05, 2021 10:31 pm
It takes ages to heat the house (metre-thick stone walls) and we have damp everywhere that's been getting worse this winter.
I’ve seen it proposed that because damp solid walls are that much less insulating than dry ones, it’s actually worth heating a damp solid walled house until the walls dry out - quite apart from the costs of having to make good damage from damp and the health consequences if damp leads to mould.

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Re: Warming a house all day

Post by jdc » Wed Jan 06, 2021 2:11 am

A decent dehumidifier (not one of the tiny ones that wouldn't dry a cupboard) worked wonders for my cold, damp flat (thin, brick walls).

Cost £150; it's a bit noisy, so I tend to use it when I'm not going to be sitting in whichever room I'm drying out; it was definitely worth it for me though.

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Re: Warming a house all day

Post by basementer » Wed Jan 06, 2021 4:31 am

jdc wrote:
Wed Jan 06, 2021 2:11 am
A decent dehumidifier (not one of the tiny ones that wouldn't dry a cupboard) worked wonders for my cold, damp flat (thin, brick walls).

Cost £150; it's a bit noisy, so I tend to use it when I'm not going to be sitting in whichever room I'm drying out; it was definitely worth it for me though.

ymmv
I agree. As a migrant Englishman I opine that it's never really cold or really hot in Wellington - not seen it go below 2C or above 29C - but we're on the coast with lots of wind coming off the sea so it's always humid. Running a dehumidifier to make it a bit drier inside the house in both winter and summer makes it more comfortable.
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Re: Warming a house all day

Post by shpalman » Wed Jan 06, 2021 11:05 am

sTeamTraen wrote:
Tue Jan 05, 2021 7:56 pm
(house maybe cools down to 10C by 1800)
Can you all please check this by leaving your heating off all day tomorrow? 10°C seems way too low.

I'm glad I live in an apartment in Italy with autonomous* gas heating.

* - so that I'm not at the mercy of when the mayor says it's ok for apartment blocks to fire up their communal heating systems.
discovolante wrote:
Tue Jan 05, 2021 8:27 pm
I reckon I'll just compare my bills.
This is what counts in the end.

But if anyone feels like collecting data there are USB temperature loggers, you can estimate the heat loss rate with the heating off on a cloudy day with a relatively stable temperature, and then measure the way the temperature rises when the heating is on for a certain amount of time and compare it to how much the meter reading changes (which will allow you to calculate the total energy expenditure). In doing so, you'll get the heat capacity of your house.

I don't really reckon that keeping a house warm has hidden energy savings compared to letting it cool and then heating it up again. Yes it takes energy to evaporate the damp (and not having damp is a good enough reason to not let the temperature drop that far) but that water gave up its latent heat of vaporisation when it condensed.
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Re: Warming a house all day

Post by Fishnut » Wed Jan 06, 2021 11:55 am

jdc wrote:
Wed Jan 06, 2021 2:11 am
A decent dehumidifier (not one of the tiny ones that wouldn't dry a cupboard) worked wonders for my cold, damp flat (thin, brick walls).

Cost £150; it's a bit noisy, so I tend to use it when I'm not going to be sitting in whichever room I'm drying out; it was definitely worth it for me though.

ymmv
We had a dehumidifier running for 3-4 months when we first moved in. It was full within a day, every day, and the damp didn't budge. It's a ~300 year old converted industrial building. There's no damp course, we think there's an underground stream running under the house and the walls are metre-thick pennant sandstone. Having done a bit of reading on old buildings I think the main problem is that we've got modern materials on top of old ones - cement mortar outside, gypsum plaster inside, and they prevent the walls from breathing properly and so damp patches are produced. We really need to use more suitable materials but unfortunately I only realised this after we had part of the house re-rendered (with cement-based render of course :roll: ) and one room completely replastered, though we did use plasterboard in an attempt (which seems to already be failing) at allowing an airspace between the board and the stone to allow things to breath.

That said, it's been in the family since 1950 and the damp spots have always been there so they don't seem to be doing any harm except aesthetically.

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Re: Warming a house all day

Post by sTeamTraen » Wed Jan 06, 2021 1:23 pm

Fishnut wrote:
Wed Jan 06, 2021 11:55 am
we think there's an underground stream running under the house
Can't you get a dowser in to check? :lol:
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Re: Warming a house all day

Post by Bird on a Fire » Wed Jan 06, 2021 1:45 pm

shpalman wrote:
Wed Jan 06, 2021 11:05 am
sTeamTraen wrote:
Tue Jan 05, 2021 7:56 pm
(house maybe cools down to 10C by 1800)
Can you all please check this by leaving your heating off all day tomorrow? 10°C seems way too low.
Our flat was 10°C when I woke up this morning, compared with about 5°C outside. But we don't have any insulation (the back is just 3m of single-pane windows with gaps round the frames), and the only heating is a 20€ fan heater we move from room to room for quick blasts.

My trusty euro-shop thermometer says we're up to 15°C now (compared with 9°C outside). Jumper, hat, gloves, tea and toast.

So from this experiment I guess we can conclude that the effects of having two people, a fridge, a computer, some light bulbs and an intermittent fan heater within a single-skin brick building gives about a 5°C temperature differential with the outside in typical-ish southern European winter conditions.


I'm wondering whether one of those oil-filled radiators would be a bit more economical, but I don't think so. The cheaper ones seem to be about 50€, which is two winter months' electricity bills, so I don't think I could make the cost back in savings and I'm not convinced the rooms would retain enough warmth to make a lot of difference. It'll be warm again by March.
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Re: Warming a house all day

Post by shpalman » Wed Jan 06, 2021 2:46 pm

f.ck that. It's officially 3°C outside but I measure 5°C on my balcony, and it's more than 20°C in here thanks to having had the heating on between 7am and 9am this morning.

It's a ~60 m² corner mansard apartment so two sides and the top are external, but today it's cloudy and in the winter I'd only get a bit of direct sun during the morning.

When my heating is "off" what it actually means is that it's set to maintain at least 19°C but as you can see it's not needing to do that today.
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Re: Warming a house all day

Post by shpalman » Wed Jan 06, 2021 5:05 pm

shpalman wrote:
Wed Jan 06, 2021 2:46 pm
f.ck that. It's officially 3°C outside but I measure 5°C on my balcony, and it's more than 20°C in here thanks to having had the heating on between 7am and 9am this morning.

It's a ~60 m² corner mansard apartment so two sides and the top are external, but today it's cloudy and in the winter I'd only get a bit of direct sun during the morning.

When my heating is "off" what it actually means is that it's set to maintain at least 19°C but as you can see it's not needing to do that today.
It's dropped maybe half a degree since I wrote that (subjectively feels noticeably cooler) and now it's 6pm so my heating is on.
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Re: Warming a house all day

Post by shpalman » Wed Jan 06, 2021 6:01 pm

shpalman wrote:
Wed Jan 06, 2021 5:05 pm
shpalman wrote:
Wed Jan 06, 2021 2:46 pm
f.ck that. It's officially 3°C outside but I measure 5°C on my balcony, and it's more than 20°C in here thanks to having had the heating on between 7am and 9am this morning.

It's a ~60 m² corner mansard apartment so two sides and the top are external, but today it's cloudy and in the winter I'd only get a bit of direct sun during the morning.

When my heating is "off" what it actually means is that it's set to maintain at least 19°C but as you can see it's not needing to do that today.
It's dropped maybe half a degree since I wrote that (subjectively feels noticeably cooler) and now it's 6pm so my heating is on.
After an hour my gas central heating has managed to increase the temperature by exactly 1°C.

In the OP
sTeamTraen wrote:
Tue Jan 05, 2021 7:56 pm
(house maybe cools down to 10C by 1800)

Then the heating comes on at 1800, they get home at 1830...
What temperature do you expect it to be in the house when they get home?
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Re: Warming a house all day

Post by sTeamTraen » Wed Jan 06, 2021 7:19 pm

shpalman wrote:
Wed Jan 06, 2021 6:01 pm
sTeamTraen wrote:
Tue Jan 05, 2021 7:56 pm
(house maybe cools down to 10C by 1800)

Then the heating comes on at 1800, they get home at 1830...
What temperature do you expect it to be in the house when they get home?
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Re: Warming a house all day

Post by shpalman » Wed Jan 06, 2021 7:34 pm

Well then the answer is yes, it does cost more to maintain your house at a habitable temperature all day as opposed to letting the heating switch off and then on again in the evening when you come home, just because your house loses heat to the outside faster the bigger the temperature difference is. The whole don't-have-to-heat-it-up-from-cold thing is one of those wrong things, but you could save energy by having the heating switch off some time before the occupants go to work.

My top tips are (a) never let your house get that cold what's the matter with you and (b) don't have the heating come on before you get home, because your house will anyway feel warmer than it is outside (unless you have ignored [a]). Then you can switch it on yourself when you stop feeling the benefit.

It's either the increasing temperature, or the warm radiators despite the cold house, which feel warmer than a stable air temperature. Not sure which. But this is also why I didn't leave my heating on all day today despite being at home.
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