Last week I was very busy. I found some old egg crates the kind of foam you put on a bed and I cut them and squeezed them into the window frames like this:
I also cut some to fit the above windows in the ceiling. They sell similar ones in camping catalogs for $15.
Then I took our old camping pads that we used in the tent and slid them behind the living room curtains like this:
With the curtains in place, you don't notice the blue pads.
I also went into our house and removed all the old doors. I propped them up on the outside of the camper along with the crates I use for recycling. In the cracks, I put empty 2 liter bottles and it has really helped with the heating bills!