ᐅ How do you install a vapor retarder in hard-to-reach areas?

Hello everyone,

Now that the beam support is exposed, I can install the vapor barrier. The installation will cover almost the entire beam support of the upper floor ceiling.

Unfortunately, there are a few spots (about 5cm (2 inches) gap between the wall and the rafters) that are very hard to reach. There are also nails hidden behind these areas, which makes installing the vapor barrier more difficult.

My idea was to leave these areas free of insulation and simply extend the vapor barrier over the edge of the beam to the wall, so that the inaccessible space is only filled with air.

Is this possible, or could too much air between the membrane and the ceiling/rafters cause moisture damage?
The rafters will be insulated with 180mm (7 inches) of 0.32 density compression wool, topped with 80 or 100mm (3 or 4 inches) of vapor-permeable wood fiber boards. Finally, vapor-permeable boards will be installed as a covering.

I would foam the areas first and then apply the membrane over them.

Tolentino schrieb:

I would foam those areas and then stick the membrane over them.

Ok, that sounds like a solution. I will look for a suitable foam then.