Currently the attic is vented and has zero insulation anywhere.
How to turn attic into conditioned space.
Codes vary from place to place but the rule of 7 for using an attic as an actual room typically applies.
Once you convert attic space into living space you need to bring it up to the standards of modern building codes.
However you do not describe the potential uses for that space and that gives me pause as to how to properly evaluate the risks of your options.
You could also hire a general contractor to oversee the project.
If you want to save money by doing some steps yourself you could decide to tackle the renovation piece meal acting as your own general contractor and hiring specialists as needed.
That means you ll need 2x10 floor joists or maybe 2x8 in rare circumstances and at least 2x12 roof rafters.
Pull down stairs won t work for an attic room so you must add a permanent staircase.
The missing piece of information is those miserable little beasts called the building and energy codes.
From my research it looks like the best option is to make the attic a conditioned nonvented space.
The attic is fairly small at about 1 000 sqf total.
If you are finishing the attic and turning the space into a conditioned attic with insulation that follows the sloped roofline at which point the gable vents become irrelevant then you want to maintain a vented air space directly under the roof sheathing to allow the board sheathing and the slate roofing to dry quickly.
A vapor retarder is recommended in cold climates.
Your stated goal is to turn your attic into a non vented conditioned space.
In cold climates attic ventilation is a common method to remove humid air.
In some cases a conditioned attic assembly may be desired where scissor trusses make it difficult to insulate the floor or in cathedral ceilings where the intent is to turn the attic into living space.
I m unsure of what to do and i m unsure of the most economical way to do it.
The average cost to add a bathroom is 8 000 12 000 depending on the size of the space and the scope of work involved a budget bathroom addition can cost as little as 5 000 6 000.
To convert your attic space you can hire an attic and loft conversions company who specialize in attic and loft conversions.