Jesus Christ you need to fix that.
As much as I love discussing my bathroom habits and the effect of cold on my schlong with people I've never met...
Years ago, before I lived in this house, it was a duplex. One of the tenants qualified for some power company program where they would insulate the place for free as long as the landlord promised not to raise the rent.
The genius contractors they sent out caulked some doors and windows shut. They, they proceeded to drill a few holes in the walls and blow in insulation.
In a balloon framed house.
They stopped when there was a big pile in the basement.

If I ever remodel, I'll tear down the interior walls and put in insulation. Theres none now. Just Vinyl siding, sheathing, studs, and plaster/lath on the inside.
It does make it easy tun run cables tho...