How to insulate a finished 1 1/2 story space

insulation

I have a 1 1/2 story portion on my house that has a finished office space and closet on one side. The room has no insulation as I've done a little work and had to take some drywall off the outer wall and the unfinished crawl space had none either. Because of this, it's hot in the summer and freezing in the winter.

I've created a simple diagram so you can see the profile of the space:

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My question is if it is possible to insulate the room without having to tear down all the drywall? And if so, what would be the ideal way to do so?

EDIT:

My plan so far is to poke a hole in the ceiling of the finished space so I can hopefully crawl up there and use blown insulation to shoot it down between each rafter to fill up the ceilings and then fill up the walls by poking holes in between the studs. In the end, the insulation would look like this:

enter image description here

Do I need to be concerned about moisture or will I create ice dams on the roof? I don't have any vapor barriers or vents it seems.

Best Answer

If you want to 'do it right' you likely should remove the sheetrock from the angled parts of the ceiling.

The problem with blow in insulation is that there's no easy way to ensure you have a proper air gap and vapor barrier. You could possibly use expanding foam insulation...but even then, that can be easier to do without the sheetrock.

Re-sheetrocking can be a chore, but it's not expensive.