Our duplex is starting construction in November, and we would like to convert our attic and use it as a hobby/storage room. Now the question is how best to proceed. We are currently diligently informing ourselves, and our builder has noted that the wall leading to the neighbors needs to be specifically insulated with cladding, due to the temperature difference between the two attics and the intermediate space between the two apartment buildings. In the roof itself, we want to do insulation between the rafters, over which the vapor barrier is laid. In addition, we plan to install a skylight. Has anyone had experience with this or done it themselves and know what to look out for, etc.?
We did the insulation between the rafters ourselves. Basically, it's a diligent job. Nothing is absolutely complicated. You need insulation material. Cut it with an insulation knife, build a cutting table on the floor from plywood and stampboards. The plywood can be used later for something else.
When the felt is laid everywhere, and the corners or crevices are well filled, put a vapor barrier film over it. Use a good membrane that allows moisture to escape, called a climatic membrane.
Tape the joints well with foil tape, floor and wall joints with foil cartridge adhesive. Support the foil with boards that are screwed to the rafters. If desired, you can lay drywall on top of it.
I can recommend AlfaFlex as an adhesive tape. It sticks like a glove and is much cheaper than similar "brand name tapes". The experts at our construction site have concluded that it is good.
Do the rest as described above and work carefully.
If you still have strength and energy (and money), you can put thin OSB or GC directly on the counter battens, so that with a little carelessness will not damage the foil immediately with boxes or shelves. The GC made the room lighter, the OSB made it darker. I would paint the OSB directly white to make the room lighter.
I once did dormer windows myself about 15 years ago (> 100 year old deformed old roof). Personally, I will NEVER do it again. This is a job for professionals, even on a straight and relatively new roof. The connections to the roof and soffits are especially important (heat, rain impermeability, etc.). Also, any replacement(s) that may be required must be installed professionally.
Plan for heating right away, and if the rest of the house has FBH, upstairs as well, to get by with the same flow temperature throughout the house.
Otherwise, of course, you'll have to hang the mains high up in the hobby room.