I'm renovating the 4th and top floor of a house built in 1906 in Rotterdam, the Netherlands. The house has masonry load-bearing walls and wooden beams. The current situation is shown in the image below.
[![enter image description here](https://i.stack.imgur.com/pNkzz.png)](https://i.stack.imgur.com/pNkzz.png)

The area in pink has the building envelope as shown in the B-B section cut below somewhere between grid lines 5 and 6. *Note: This space currently is not insulated.*

[![enter image description here](https://i.stack.imgur.com/V7hdL.png)](https://i.stack.imgur.com/V7hdL.png)

The mason wall shown in the image below will be destroyed.

[![enter image description here](https://i.stack.imgur.com/o3McP.jpg)](https://i.stack.imgur.com/o3McP.jpg)

The image below is taken from the 4th floor looking at the top of the 3rd floor ceiling after the floorboards were removed.

[![enter image description here](https://i.stack.imgur.com/NqyMj.png)](https://i.stack.imgur.com/NqyMj.png)

A glass facade will be installed 1 meter behind the location of the existing masonry wall thus creating a balcony that is 1 meter longer than it is currently. This is shown in the proposed floor plan below.

[![enter image description here](https://i.stack.imgur.com/azAGS.png)](https://i.stack.imgur.com/azAGS.png)

In an ideal scenario, this entire 3rd to 4th-floor building envelope would look like the following section. *Note: Rockwool insulation and vapor barrier added*

[![enter image description here](https://i.stack.imgur.com/MzHsI.png)](https://i.stack.imgur.com/MzHsI.png)

However, this is not possible since the 3rd-floor ceiling cannot be removed.

Ideally, there is insulation in the floor cavity and therefore a vapor barrier is required. Is it a good idea to wrap the vapor barrier around the floor joists as shown in the section below?

[![enter image description here](https://i.stack.imgur.com/6BFvz.png)](https://i.stack.imgur.com/6BFvz.png)

I’m worried this may cause condensation to occur around the floor joists which is the last thing I want. If that could happen I would prefer to leave the space un-insulated, unless someone has a different idea?