/ Central heating, on a timer or on constantly?
Depends on the construction I suppose. We live in a 200+ yr old stone cottage and it is definately cheeper to leave the heating set to a constant 15deg. Does take a couple of days for the walls to cool down, but let that temperature drop and it takes a good 24hrs to take the chill off.
I think it that you don't neat the fabric of the building, you basically just heat the air. Better to have the heating on so the air is warm when you get home or get up.
I live in old diggs with single glazing. The heat goes out really fast when the heating goes off. Keeping the place warm when I'm at work would break the bank!
We are trying that experiment now. We've got a 1930's house which is drafty and leaks heat (ongoing issue we are working on). If the house fully cools down then it takes 24-36 hours to get back to temperature, so we thought we would experiment.
Hence this winter we tried keeping the heating on continuously, and last winter we tried the on-off technique.
More accurately, this winter we heated the upstairs continuously (heating never off but controlled by roomstats), and downstairs was continuously heated 6am-11pm (also controlled by roomstats).
TRV's on all radiators.
Anyways, we got the gas bill for the winter a couple of days ago, and the result appears to be that it's about the same to heat the house continuously rather than on-off, however its *certainly* more pleasant to be in a house at a constant (warm) temperature. This rather surprised me as its counter-intuitive that on all the time is the same.
Total energy used for both winters (Nov-Feb) was around 15000 kwh.
your aunt is right - according to Jeff Howell:-
Thanks John for doing the experiment and reporting it. I am in a similar situation though not a similar house, mine dates from about 1810 and the cold has different causes to just draughts, but I've often pondered what would happen if heating were left on constantly...but never done the experiment.
Constant. I control the heating with the room stat in the hall.
Our heating never really goes off, or n timer. It has a modern controller. You can set the temperature to be maintained at certain times if day, and by day of week. So you have complete control, keep it high all time, or allow to dip a little during day, or hotter during day, cooler at nigh etc.
Interestingly, we've had cavity fill since and the gains since the curtains are marginal - the house was already well insulated, air change/draughts being the biggest cause of heat loss.
Theoretically, allowing the house to cool down when you are not there and then heating it up on a timer for when you are at home should be more economical since the rate of heat loss (which therefore needs replacing) is lower when the temperature difference between the inside of the house and the environment is lower.
I have good double glazing and loft insulation but as house was built around 1800 there is no wall cavity, just thick walls, and no underfloor cavity either.
Last year heating (and hot water) cost £189 per month!!
I'm considering just heating the living room and putting more blankets on the beds!!!
My thought would be it would vary from case to case and would depend upon the relative magnitude of the heat flow through the wall and the strength of the convective flows within the room/house. It may be that houses always fall into one category (I've only ever worked in dimensionless parameter space so have little feel for practical magnitudes) but I don't believe the theory always points to one case.
This means on warm days you're not trying to heat the house so far up above outside temp.
According to the link above it seems it's more about condensation in the walls reducing their thermal efficiency when a house is allowed to cool down, and the heating on all the time approach won't work if it's draughty.
20C? That's a f**king sauna! Ours is on 16C for an hour or so in the morning to take the chill off then for about 4hrs in the evening.
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