Minimum insulation of exterior wall for wardrobe?

[lc155]

Hi,

Have an exterior wall (cavity behind it is ventilated with outside air as in roof space), west facing. The old wall is just your standard lime plaster on wood laths that are basically strapped straight to the stone. Want to tear it all down and insulate, as I have had issues with small patches of mould forming on the backs of wardrobes close to that wall before.

Keeping mindful of space, I was hoping to get away with battening out with 2x2s and infilling with 50mm PIR, then slapping 25mm over the top of it all to stop cold bridging from the studs.

When done, I want to put a couple of PAX wardrobes slammed right up against the wall (this is the only good wall to have a wardrobe in that room). Would be used for clothes and storage of various items I wouldn't want getting damaged due to poor conditions.

Looking at internet calculations, 75mm of PIR in this configuration would give me a rough U value of 0.3. What I'm mostly concerned about, though, is will this entirely solve the problem of that wardrobe getting too cold? Ultimately, I'm just not sure how much insulation is 'enough' to have the wardrobe on an exterior wall basically be equivalent to if I was putting it on any other wall where these issues would never be a problem.

 

[^woody^]

The amount of insulation required to prevent condensation is different to that required to insulate a wall. It can be as little as 5 or 10mm.

If you insulate a wall there is no guarantee that the air within the wardrobe or at the room corner will not still condense on the wardrobe back panel. Mould feeds on the fibres or glue of man-made panels.

So fundamentally, there is no point in trying to work out what is enough. You are better off thinking more generally about dealing with the excess humidity that may cause mould in the first place.

 

[lc155]

The amount of insulation required to prevent condensation is different to that required to insulate a wall. It can be as little as 5 or 10mm.

If you insulate a wall there is no guarantee that the air within the wardrobe or at the room corner will not still condense on the wardrobe back panel. Mould feeds on the fibres or glue of man-made panels.

So fundamentally, there is no point in trying to work out what is enough. You are better off thinking more generally about dealing with the excess humidity that may cause mould in the first place.

I was thinking about standard levels of humidity. 50-60%, nothing excessive really. It was just with an obviously extremely cold outer wall, that wasn't enough to prevent damage from condensation, even if it was only small amounts over time and nothing visible on the wall itself.

I take it then that the amount of insulation plus those levels of humidity are sufficient?