ᐅ OSB boards or tongue-and-groove planking for the floor in a convertible attic?

Hello everyone, I have covered the first half of the attic floor with tongue-and-groove boards. Now I want to install some additional insulation between the rafters to prevent it from getting too cold or too hot. However, I’m still unsure about the vapor barrier. I have already installed one, but I didn’t make sure it is completely sealed to all the other building components. For me, the vapor barrier is just supposed to keep the insulation from being exposed. Is that okay? Or does the vapor barrier still need to be perfectly sealed even in a somewhat leaky attic?
Thanks and best regards

Try to glue the corners as well to ensure it is sealed. I'm not a carpenter or joiner, but I did this with a relative who is. He said it needs to be airtight. He also said it should act as a brake, not a stop.

If you have a vapor retarder in the ceiling between floors, that would not be a problem. Without an additional vapor retarder, your insulation could become damp. To answer this properly, one should understand the purpose of a vapor barrier or vapor retarder.

The goal is to protect the insulation from moisture coming from the indoor air. Dust protection or the physical separation from the living space is a secondary effect.

So,
- Do you already have a vapor retarder in the ceiling between floors? This is common in bungalows with cold roofs.
- Does the roof have a vapor-permeable underlay membrane beneath the roof covering? This protects against rain but allows water vapor to pass through to the outside.

Hello and thank you for your feedback. I can answer both questions with yes. There is a vapor retarder on the ceiling of the upper floor (gable roof with an unheated attic). And there is a vapor-permeable underlay beneath the roof covering.

Hello!
So, how did you end up solving the issue?

Hello, I haven’t done anything yet. I’m still not sure exactly what I should do now 🙂