Insulating a slanted wall / cavity before or behind insulation

Since we are currently also dealing with the topic, my current level of knowledge: HausiKlausi is right, basically an external insulation is preferable to an internal insulation - less prone to errors, often cheaper, and no loss of living space. Opinions differ on internal insulation - partially dramatically :D But what they all have in common is either a ventilated two-layer structure or a cavity-free (!) single-layer internal insulation with capillary-active insulation materials, e.g. calcium silicate boards or Multipor. However, this is especially important if it concerns often/permanently heated rooms (possibly even wet rooms) and as a result, condensate forms within the wall structure, especially in winter. If it is just a makeshift hut anyway, you can deviate from the usual structure if necessary. Btw: Wall structure can be well simulated on ubakus. Unfortunately, the program does not yet understand "capillary-active" insulation materials, i.e. do not be discouraged if the program shows a condensation problem for Multipor, for example. The program, however, understands ventilated structures well ;)

do not wallpaper, the musty smell after the winter break is wallpaper and glue

don't worry, I wrote "Inside I plan to install a vapor barrier over the insulation and then cover the wall with 12mm multiplex boards" :)

then to clad the wall with 12mm multiplex boards" :)

Multiplex and moisture are not exactly a great duo.

what do you suggest? It’s not exactly uncommon these days, especially in modern architecture, like here: And there’s a vapor barrier under the multiplex, so nothing should get damp there, right? Or what do you mean?

Well, with internal insulation there will be a dew point inside the insulation in winter. Because warm air holds more moisture than cold air. A vapor barrier would prevent this, but only if it is 100% airtight. Since this is usually difficult to impossible to achieve, internal insulation is generally strongly discouraged.

However, the construction is not ideal now either with wooden battens, Styrofoam, roofing felt, tongue and groove cladding. It will probably condense somewhere around the Styrofoam and roofing felt (layman's opinion!) at 20 degrees inside the hut and 0 degrees outside.

To what extent this causes greater damage to a garden hut, which may only be used and heated rarely in winter, I don’t know. Probably less. Had you already mentioned how the building is going to be used?

But maybe a professional will come by :)