Thinking aloud: supplementing inside insulation by outside insulation?

[Garald]

I've already bored many of you with my story, but, quick recap: on the south side, I have a thick layer of BioFib Trio as insulation, but, on the north side, I have a much thinner layer (5cm I think) plus reflective insulation (which comes with its own insulating backing, obvs).

 

So far, everything seems good, but plenty of people here have doubts that reflective insulation works as well as advertised. A thermal camera shows nothing terrible (just that the frames are very visible under the thermal camera on some spots of the north side). Still, I wonder whether I am as well insulated as planned.

 

I obviously don't want to scrap everything that has been done without good reason. But what if, at some point in the next few years, I have the budget to do further major renovations? Would it make sense to add insulation on the outside of the north wall? Which kind?

 

Obviously it would need to be a kind of insulation that "breathes", to prevent condensation. (The wall itself is masonry, hence porous.)

[SteamyTea]

I think it is always worth insulating, especially a North wall as that gets very little sunshine on it.

As for what sort, it is usual to use a sheet foam, a fireproof one.

 

[Garald]

2 hours ago, SteamyTea said:

 

As for what sort, it is usual to use a sheet foam, a fireproof one.

 

 

Fireproof - so neither PUR not PIR, but rather what?

[Garald]

Also, isn't much foam insulation non-breathable? As I said, this is a masonry wall.

 

From what I read, there is also wood fibre (though that can be expensive). Is that a possibility? What are the downsides?

[SteamyTea]

39 minutes ago, Garald said:

Fireproof - so neither PUR not PIR, but rather what

They have fire retardants put in them.

Though there is a review going on about how good after the Grenfell fire.

Worth checking what the rules are in France, especially Paris, if they are different.

[Alan Ambrose]

You could check any of the proprietary external wall insulation (EWI) systems - Sto / Dryvit / etc. You can buy their products or replicate some of their not-very-complicated design detail. So EPS/PIR/mineral wool behind rainscreen of some sort, with a vapour barrier if desirable.