How to improve thermal efficiency of one room?

27 Mar 2021
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United Kingdom
Just looking for some advice, we have a detached home built in the late 90’s that has both cavity wall and loft insulation and a mix of single and double radiators.

The boiler was replaced 4 years ago.

The South West corner bedroom is exceptionally cold in cooler weather and exceptionally warm in hot weather and I am looking for any ways to improve the thermal efficiency of the room as this is the nursery.

At present, the external temperature is around 5°C and the ambient temperature of the room is 14°, the wall temperature is around 14.5°, this is in comparison to the room below that has a wall temp of 17° and the adjacent (South East corner) room that currently has a wall temperature of 19° and an ambient temp of 20°.

By this evening, after the heating has been on, it will get up to 19/20° by around 7pm - it will then drop during the night to 14-16° dependent on how cold it is outside.

Likewise in warmer weather it is significantly warmer than other rooms. The typical variance is 2-3°.

It has a double glazed window and a single radiator.

Any suggestions?

The room is closed during the night as I have a baby and a toddler and I don’t want one to wake the other up during the night although I suspect the lack of air circulation probably compounds the issue.
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Do you measure loft insulation in depth? It’s the same as the rest of the house quite deep - at least 5cm. If you want an exact figure I will have to go up in the loft and check.
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You may be getting air leakage into the cavity. Wonder if the cavity insulation was the loose stuff & its settled?
As above re loft insulation..
Have you tried blocking out the sun during the hours that the window is in full sunlight, when the room is likely to get too hot?
Helen, Herts is correct that loft insulation should be your first step. It's cheap and quick to upgrade and you could do it yourself. 300mm deep is the current standard. Air loss is next, check the window seals to make sure they are good. If you want the room to warm quicker and be a bit more controllable you might consider upgrading the radiator and thermostat. Next step would be internal wall insulation which is messy, expensive and disruptive, so do the other things first.
Thanks all. Insulation is 300mm, have checked - actually slightly more.
Seals on the window seems good so going to upgrade to a double radiator.
Just need to find the time as we have two small kids and husband will fit it.

Does anyone know if thermal wallpaper is worth it?
We had exactly the same problem with a corner bedroom and a bathroom with solid brick wall. We insulated the walls with thermaline
"Gyproc ThermaLine PIR
Gypsum plasterboard with integral vapour control layers for an advanced level of thermal insulation.

12.5mm Gyproc WallBoard bonded to CFC and HCFC-free meaning zero ODP (Ozone Depletion Potential), high performance polyisocyanurate foam insulant with two integral vapour control layers to reduce the risk of condensation. Designed to be used in both refurbishment and new build for walls, ceiling, room in the roof and window reveals where a high level of cost effective thermal insulation is required to reduce heat loss from buildings as part of our British Gypsum BBA approved systems."

We just screwed it to the walls with long screws and plugs. You have to alter the skirting, door frame, and power sockets and window ledge Etc. Also the built in aluminium lining tends to reduce wifi and mobile phone reception in the room. It certainly worked though and well worth doing. The bathroom was a nightmare doing as you can imagine. We ended up doing all the external walls over a number of years, especially the stair wall. You can get different thickness of the plasterboard. The stairwall we got fire retardent PB for the lining as we were a bit wary of having a fire on the stairs and not being able to get out. You do need to get Building regs people involved otherwise you can't get an EPC cert. for the work when you come to sell. Which we found extremely frustrating.
The stairwall we got fire retardent PB for the lining as we were a bit wary of having a fire on the stairs and not being able to get out..
Ignoring the silly fire retardant PB bit, how would you get past a fire on your stairs anyway and how would a fire start on your stairs? Probably the least likeliest area in a house where a fire might occur?
To continue this thread. If you don't intend to stay in the house at least 10 years, do as a previous respondent said, get a double rad and put a thermostatic valve on, but this does mean you need the heating on all the time. As long as you have TRV's on all the other rads it doesn't raise a problem. The new TRV's work fine and last five years before needing replacing. Much more cost effective of you are intending not to stay very long in the house. Thermal wallpaper is just ridiculous mumbo jumbo and you will realise can't possibly work if you have any sort of science education.

P.S. kids love helping to do that sort of job, no matter the age. It will possibly increase their vocabulary as well!!
No no, fires don't start on the stairs. It's your escape route...NEVER compromise it. Look at Grenville
So in your house do you have sprinkler system and smoke/heat detectors in every room too? Fire doors and closers on every habitable room?

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