Why is my home so cold??

[Freshstarts24]

I’m hoping someone might have some ideas as to what the issue could be. I live in a flat, have gas central heating. The flat is fairly old , but has double glazing and doesn’t feel particularly drafty.
No matter how long I have my heating on or what temp I turn the thermostat to it does not seem able to go above 21 degrees. Now, I’ve seen others mention on here that 21 is a reasonable temperature, but in my flat it still feels chilly. Whereas 21 in my office for example, would not be.
Surely it can’t be right that I can’t get the temperature any higher than this? It’s never warm. If I have the heating on for 5 hours, it stays at 21, and whilst no longer cold, it’s also not warm.

You probably don’t have enough insulation between the floors. Do you have thick curtains with insulation in them?

It's probably to do with insulation. Could you get some kind of assessment done on it to see if it could be insulated better.
Here in lreland we have grants for that but maybe not in the UK

Is it actually hitting 21 degrees? Does the heating actually click off if the thermostat is set to 21 I mean, or is it constantly trying to get there?
Have you bled the radiators? Are they hot along the whole radiator? Are the individual radiator thermostats turned up?

On a cold day, 5 hours isn’t much. It gets cold then takes ages to heat up again. We are low heat for longer. We like window open a bit at night.

Could it be damp? That always makes a room feel colder.

What did the EPC rating say when you bought or rented the place? Check if it is a low rating and what assumptions it made (e.g no cavity wall etc) and it should also state what solutions would help.

Also what direction does the predominant side of the flat face? North facing can makes places colder.

I have decent enough curtains in the bedrooms which are the coldest rooms. A good 3 degrees colder than the living room.

Yes it reaches 21 but no higher. I haven’t actually felt the whole radiator so I’ll try that but they do feel very hot. Haven’t been bled. Yes they’re all turned up as high as they’ll go.

Is the temperature on your thermostat correct. Mine read 24° but it's actually 21, so I just turn them up higher knowing they are a few degrees out

One of the bedrooms has a tendency for damp. I use a dehumidifier in there. But it’s definitely the coldest room.

I don’t know what an EPC rating is and am not really sure which way it faces. Living room and one bedroom faces one way and everything else another.

No idea no just no it’s never warm and no matter what I turn it up to I can’t make it any warmer. My old place was a similar building in terms of age and size and I never had this issue.

As suggested check each radiator as they might be filled with more air than water. Bleed them to get rid of the air.
Have you checked for draughts? Around doors & windows? Vents?
Do the walls feel cold?

High ceilings and tall windows could be a factor. Older double glazing may be less effective. Laminate flooring or varnished boards will be less cosy then carpets. Thin unlined curtains may not be as good as keeping heat in as longer, thicker, lined ones. The number and size of radiators is another thing to consider. One small radiator in a big room may not be enough.

It sounds like your thermostat is clicking off at 21 and just staying at that temperature. My flat doesn't feel warm unless I set it to 22.5

Have you had your boiler serviced? Also where is the thermostat for the heating? As in where is it registering the temperature, vs where the controll unit is? If the thermostat is near a heat source it may turn off even though the rest of the flat isn't at temperature.

Many people have under sized radiators. Or single ones when double would be better. Thick curtains with a thermal interior are better for keeping the heat in. Not standard curtains. Definitely get rugs. I’m happy to wear a fleece inside. Plus a cool bedroom is better for sleep.

EPC - energy performance certificate.
Satellite dishes on houses face south. You could use this to work out your flat’s orientation, or note which window looks out on sunrise or sunset.

Are all your radiators unobstructed by furniture?

Have you gone through your boiler settings? It could be capped at 21 degrees, so it doesn't go any higher?

My tight ex FIL capped his at 19 until my ex MIL learned how to override it 🤣

Might you have crap old radiators? Our house has a mix of old and new ones and the rooms with new ones are much, much warmer than those with the old ones.

Have you checked the temperature with a separate thermometer? Could the thermostat be a few degrees off? 21°C should feel really toasty, like you describe your office. At that temperature, you'd be able to wear short sleeves indoors in winter. We're comfortable at 17-18°C, and I know that's the accurate temperature as have both a thermometer and the thermostat on the wall.

Set your thermostat to 24C. Mine is usually 22-23C.

Get a thermometer for the rooms and compare the reading on that with the reading on the thermostat. My friend's thermostat seemed to think it was 21 degrees when the separate thermometer said it was only 19.

Under floor insulation, radiators that don’t have enough output for size of rooms. Regularly dehumidify the whole flat and actively ventilate by opening your windows for 20 mins in the morning – dry air is easier and faster to heat than damp air.