Insulating a very cold corner - seeking advice!

[clockworksatan]

Hi all,

This is my first post here, please be gentle!
Basically, I'm looking for some advice... To the right of the back door in my house, there's a small corner which gets incredibly cold, mainly due to the fact that the outside wall where it gets cold is not - and cannot be - insulated for various reasons. It's a 1950's concrete extension that's not been planned or executed as well as it could have been!
I made an attempt at insulating the corner a while back by building a vertical box and stuffing it with insulation material (see picture below), but it became clear in the winter that the coldness of the wall penetrates further into the pillar to the right of the door than I expected it to, and when the warm air in the house hit the cold wall, it started to form condensation and - inevitably - mould.
I've made peace with the thought of ripping the vertical boxing off and starting again, but I'm not sure what the best solution would be. I've been thinking of using insulation boarding on the cold wall instead of stuffing a cavity with insulation wool, and boxing it in and covering it with hardboard - would this work, or would it be better to create a wider cavity and stuff it with wool insulation?
I'd be grateful to receive advice, suggestions of other potential solutions.
Thanks.

 

[Mr Chibs]

Is there insulation (rock wool) behind the big skirting board boxing?

Is it mouldy in the corner at the floor... looks like it is.

You may be better putting kingspan on the arched wall and re-plasterboard, at least then you will break the cold bridging, and hopefully move the dew point, I realise it's not that straight-forward

Can you take an outside pic of this area please.
You would be better with external insulation, but you'd need to render/clad when finished... expense!

 

[clockworksatan]

Is there insulation (rock wool) behind the big skirting board boxing?

Is it mouldy in the corner at the floor... looks like it is.

You may be better putting kingspan on the arched wall and re-plasterboard, at least then you will break the cold bridging, and hopefully move the dew point, I realise it's not that straight-forward

Can you take an outside pic of this area please.
You would be better with external insulation, but you'd need to render/clad when finished... expense!

Sorry for the delay in my reply!
There is some insulation behind the skirting board boxing, which has actually worked fine.
The colour of the flooring is the result of another problem; a badly replaced guttering above me (done by the upstairs neighbours without my consent!) that resulted in water coming underneath the back door. It's what caused the MFD boxing to go puffy, but the flooring isn't mouldy - just unpleasant to look at - the reason I want to get this job done is so that I can put down new flooring in my hallway.
I can't use plasterboard either - the bit to the right of the door is actually a concrete pillar, so my only option is to use insulation boards or wool and box it in, I think?
The external bit outside is basically a small alcove where the upstairs waste pipe runs down. There's no way it can be insulated externally or internally.

 

[foxhole]

Mould is not inevitable, its the result of poor ventilation.

 

[clockworksatan]

Mould is not inevitable, its the result of poor ventilation.

Not in this case, it's not. It's the result of warm air hitting a cold concrete wall/pillar which has as much ventilation as it's ever going to have - hence I'm looking for helpful suggestions on how to best insulate it.

 

[foxhole]

Warm air hitting cold wall creates condensation , not mould which is a result of mould spores settling due to lack of ventilation .Condensation is also removed by adequate ventilation .