Vapor barrier or retardant, or nothing?

[Holmfrid1]

I have a cabin with heating year-round, at least 15 degrees.

It's time to replace the panel, and hopefully, it will be done next summer along with additional insulation externally with 45mm.
Currently, it's -panel-asfaboard-95mm fiberglass-timbers in one part, and in the other part, it's plastic and chipboard directly on the frame.

The big question now when I also plan to add internal insulation with 45mm is how should I do it?

-Option1: I remove the timbers then put a vapor brake, frame 45mm, and OSB+gypsum?
-Option2: Leave the timbers as is, then put a vapor brake, frame 45mm, and OSB+gypsum?
-Option3: same as 1 but vapor barrier.
-Option4: same as 2 but vapor barrier.
-Option5: leave it as it is and add insulation?
Suggestions:

 

[klaskarlsson]

I have a cabin with heating year-round at a minimum of 15 degrees.

The panel needs to be replaced and hopefully, I will replace it next summer and add additional insulation externally 45mm.
Currently, it's -panel-asfaboard-95mm fiberglass-rote in one part and in the other part, it's plastic and chipboard directly against the stud.

The big question now is, since I also plan to add internal insulation 45mm, how should I do it?

-Alt1: I remove the rote then put a vapor retarder, stud 45mm, and OSB+gypsum?
-Alt2: Leave the rote as it is, then put a vapor retarder, stud 45mm, and OSB+gypsum?
-Alt3: same as 1 but with a vapor barrier.
-Alt4: same as 2 but with a vapor barrier.
-Alt5: leave it as it is and add insulation?
Suggestions:

If you don't have any barrier/retarder today, you can just insulate and install a retarder/barrier on the inside. Generally speaking, 45mm is what most installation layers are (where the retarder/barrier sits between this and the main insulation), but then the main insulation also needs to be thicker so you don't get the cold side wrong.

Personally, I prefer a vapor retarder instead of a barrier because it's difficult to ensure everything is tight in old houses, and it feels better if the moisture can find its way out again if you can't get it completely tight in, for example, joints between new and old... but there are different schools of thought.

 

[Holmfrid1]

If you don't have a barrier/brake today, you can just insulate and put a brake/barrier on the inside. Generally, 45mm is what most installation layers are (where the brake/barrier is placed between this and the main insulation) but then the main insulation also needs to be thicker so you don't have the cold side wrong.

Personally, I like a vapor brake instead of a barrier because it's difficult to guarantee that everything is sealed in old houses, and it feels better if the moisture can find its way out again if you can't get it completely tight, for example, in joints between new and old... but there are different schools of thought.

Yes, exactly, usually a 45 is laid, but I think it will be quite similar when I then add exterior insulation 45mm 🤔
But I'm not sure how you think I should do it😅, do you mean that I should set up 45 on the frame and insulate, then put on vapor brake, and so on, plasterboard?

 

[klaskarlsson]

Yes, usually a 45 is added, but I think it will be quite similar when I then add external insulation of 45mm 🤔
But I'm not sure how you suggest I should do it😅, do you mean that I should frame 45 on the rote and insulate, then use a vapor barrier-and-clamp-board-and-so on-plaster?

If there is no vapor barrier/break today, you can frame 45mm on the existing wall, insulate, put on a vapor barrier, and then add plaster/inner wall, I would say.

If there is already some form of vapor barrier in the wall, I would skip the vapor barrier on the inside because you don't want to trap any moisture between two layers, even if it's a break instead of a barrier.