Why is my house so cold?

[Winterbeee]

We live in a newish house (about 20 years old), have double glazing, cavity wall insulation, tonnes of insulation in the loft and yet still parts of the house are so cold, particularly the hallway and one of the bedrooms. Strangely other parts of the house are so badly effected. What have wise MNers tried that have improved things? Is there a type of contractor that could tell me what's causing the problem and how to go about fixing it? TIA!

Are you sure about the cavity walls filled?
My house was built in 1994 and had hollow walls, only 10 cm of insulation in roof, too.

Do you get condensation problems -- this would suggest low draughts.

Following with interest, to see if OP ends up as snug as a bug, in a rug

Does that room have two outside walls? A semi detached house we were renting had one very cold bedroom - the one with the two outside walls, which was above the hall, which also had two outside walls and a not so great front door. The hall never seemed as cold as the bedroom did though, and the landing wasn't bad either, and nor was the upstairs bathroom, which also had two outside walls. There was plenty of insulation in the attic but I think the outside walls weren't well done, or at least the one at the front of the house wasn't.

It is a common corner cutting practice in New builds, because it's so easy to get away with it when it's all hidden and only comes to light a long time later.

"the thermostat is in the living room, which is one of the warmer rooms in the house."

That will be the trouble. The heating system should be adjusted so that the3 room with the stat heats up slower than all the others. Otherwise it will turn off the heating while other rooms are still cold.

Luckily this is quite easy.

Look at the valves at each end of your radiator. One will have an adjusting knob, either a TRV or a manual control. Look at the other end. This can be adjusted to reduce the rate at which the radiator heats that room. Can you photograph it please?

Hi @lljkk, the people we bought the house from told us they had got the cavity walls filled- I hate to think what it was like before! We hadn't asked them about it, they'd volunteered the information so I'm pretty sure its been done. Of course, I've no idea what standard the work was done to. We don't really suffer from condensation, sometimes a tiny bit once in a while but its pretty infrequent.
@Apileofballyhoo the cold bedroom actually has three outside walls. I don't know if it makes any difference, but its not on the exposed side of the house that takes the brunt of the weather, weirdly most of the rooms on that side are warmer, even the ones with a couple of outside walls. The cold hallway doesn't have any outside walls (other than the actual front door), this however is on the more exposed side of the house. We're in fairly rural, exposed location, so we can get pretty battered by the wind and rain during the winter, however the cold bedroom is in a part of the house which is actually quite sheltered and protected.

Thank you so much @PigletJohn. Please find an image attached.

@MacbookHo

Haunted?

When first married we rented a 1930's bay fronted house on a short term contract.However there was something uncomfortably eerie about the small bedroom plus it was really cold in there, even in the summer. Shortly before we left to work abroad had a chat with the old lady down the road. "I bet you didn't use the box room" , " Couple who lived there lost their baby. Poor thing died in that room". Years later in that part of London drove past, no house. Dropped into the newsagent and asked about no 15, "Burnt down, started in the kiddies room".

@Winterbeee
using a small screwdriver, take out the screw holding that protectice cap. Under it you will find a spindle with a flat.

Usig either a manual knob taken off another radiator, or your 80mm small adjustable wrench, screw the spindle in until it stops. Wait half an hour and you should find the radiator is now fairly cool, and so are both the pipews going into it.

Open it half a turn only and wait 15 minutes. Are either of the pipes now warm? If so, leave it. If not, open it another quarter-turn only. Do not open it by more than a quarter turn in any 15 minute period.

Meanwhile, go and feel your other radiators. Are any of them any hotter? The flow pipe at one end (supplying the hot water) of each radiator should be "too hot to hold" and the one at the other end should be "quite warm to fairly hot". Is that the case on all radiators?

a wall insulation filling company will drill a few tiny holes in your walls & see if there is filling there. They can show you (look down their scope) so you see for yourself. I would not believe what previous owners said.

You could even have some walls filled & other walls not filled

Thank you @PigletJohn, this is so incredibly useful, its very much appreciated. I'll report back once I've checked them all.
That's a good point @lljkk, its probably worth getting it checked over by an insulation company.

This won't help your real insulation problem, but I have one coldish bedroom with 2 large windows. In winter I keep the curtains closed when I go to work. Heating is on thermostat and timer very low during the day. Come back in the evening and the room is toasty warm. It's freezing at the weekend when I have the curtains open all day. I wouldn't have believed the difference floor length curtains could make until I noticed this.

Piglet is totally right but what would help you is thermostatic valves as well on each radiator. They are a bit rough and ready although apparently the ones you can have with Hive are better

Having the main thermostat in the living area will mean the heating switching off for the whole house when it is warm enough. Ours is in the hallway which is the coolest part of the house.

When we bought it originally the boiler was exactly sized to the original house and had been extended a little as well. This meant when the weather was cold the heating would take ages to warm up and the boiler never switched off. The burners were going constantly. DH balanced the radiators which took days to do but improved the situation and ensured water wasn't being returned to the boiler too hot.

What made the difference was a new boiler! We doubled the capacity and the difference was incredible. System hot within 20 mins . Could feel the heat belting out!

Yes to adjusting the valves. Other things that occurred to me, is it damp? Damp rooms take more heating as you need to warm all the water too. Do you keep the door shut? Should stop any draughts coming from the stairs/landing.