It completely depends on how you have constructed the wall. Please explain!
If you have the plastic on the innermost side, before the drywall or other cladding, then it’s simply a matter of filling the space between the wall stud and the frame from the inside with dense foam or plastic-sealed packing.
In a super-insulated so-called passive house, you must tape this part of the house as well to prevent any vapor leakage around the window mounting. Special age-resistant tape is used for this.
If you have the plastic on the innermost side, before the drywall or other cladding, then it’s simply a matter of filling the space between the wall stud and the frame from the inside with dense foam or plastic-sealed packing.
In a super-insulated so-called passive house, you must tape this part of the house as well to prevent any vapor leakage around the window mounting. Special age-resistant tape is used for this.
Here's a bit more explanation:
* I have 45*170 wall studs that the window is attached to, and the window is set according to the exterior paneling. The windows are insulated.
* On these wall studs, the plastic is on the inside, and inside these, I have 45*45 and cladding boards.
So I need to somehow attach the plastic to the frame now... as it is, it's just lying there. Maybe I should take the plastic and tape it to the frame? According to "traguiden.se," you should use some rubber gasket here...
And I'm not building a passive house, but I will have FTX ventilation, so it should be fairly tight around the windows.
* I have 45*170 wall studs that the window is attached to, and the window is set according to the exterior paneling. The windows are insulated.
* On these wall studs, the plastic is on the inside, and inside these, I have 45*45 and cladding boards.
So I need to somehow attach the plastic to the frame now... as it is, it's just lying there. Maybe I should take the plastic and tape it to the frame? According to "traguiden.se," you should use some rubber gasket here...
And I'm not building a passive house, but I will have FTX ventilation, so it should be fairly tight around the windows.
We cut the plastic so that it could be folded into the rebate. Taped the plastic and then into the gap between the frame and studs. After that, the backing strip locks the plastic in the gap, and then it's sealed on the outside with a soft sealant... Then it becomes completely airtight!
Precis.
Fold the plastic and attach it around the studs in the window opening.
Insulate the window (or foam). Leave 3 cm free towards the inside.
Insert a backing rod of foam plastic.
Seal with acrylic sealant from the inside, so it’s tight against the plastic and the frame.
edit:
It might not be ordinary painter's sealant that's needed.
What is best?
Fold the plastic and attach it around the studs in the window opening.
Insulate the window (or foam). Leave 3 cm free towards the inside.
Insert a backing rod of foam plastic.
Seal with acrylic sealant from the inside, so it’s tight against the plastic and the frame.
edit:
It might not be ordinary painter's sealant that's needed.
What is best?
Suspected just that, it probably hardens way too much.
Nice thread lift, my post was from 2009 
The backer rod clamps the plastic film against the stud, so the joint doesn’t really need to adhere to the plastic. It's still in the right place.
This is what a backer rod looks like for those wondering; they come in different dimensions, and some brands have a hole in the middle (like macaroni). I bought mine from Biltema, which at least at that time was well-priced, but I don't know how it is today.
Choose a diameter that fits the gap between the frame and the window hole-
However, some just pull the vapor barrier a few mm over the frame and tape it to the window frame. But then you can't insulate from both sides, and there's a high risk of damaging the vapor barrier on the inside while insulating the outside. Well, on the other hand, you can insulate before finishing by attaching the vapor barrier.
The backer rod clamps the plastic film against the stud, so the joint doesn’t really need to adhere to the plastic. It's still in the right place.
This is what a backer rod looks like for those wondering; they come in different dimensions, and some brands have a hole in the middle (like macaroni). I bought mine from Biltema, which at least at that time was well-priced, but I don't know how it is today.
Choose a diameter that fits the gap between the frame and the window hole-
However, some just pull the vapor barrier a few mm over the frame and tape it to the window frame. But then you can't insulate from both sides, and there's a high risk of damaging the vapor barrier on the inside while insulating the outside. Well, on the other hand, you can insulate before finishing by attaching the vapor barrier.