Opinions on roof insulation from the inside

Hello everyone,

We will soon be renovating a house from 1980 with a pitched roof.
1.5 floors + an attic, which is used as a storage room. Possibly later as a playroom or office. (Private)

I am now asking myself how to approach the topic of insulation.

Currently, the roof is constructed as follows:

-Roof tiles
-Air layer
-Delta foil
-Glass wool

The Delta foil is now porous and partially no longer intact. The glass wool here and there is also no longer what it once was.

The first roofer suggested a complete reroofing with continuous insulation above the rafters.
Costs around €16,000-18,000.

Since the roof is still in good condition, I currently consider that unnecessary.
Everything will come down from the inside, so we have good access.

I now have 3 options in mind:

Option 1:


Retrofit installation of a secondary roofing membrane
1 = rafters possibly with doubling up
2 = insulation material
3 = diffusion-open secondary roofing membrane fixed on the sides with battens
4 = roof battens
5 = vapor barrier

Option 2:
Do without a secondary roofing membrane and instead make the air layer somewhat larger.

Option 3:
Remove roof tiles in own work, install secondary roofing membrane, put roof tiles back on.
Then as in Option 1

I tend towards Option 1.

Does anyone have experience or tips?