Having a wall between you & the cargo area is helpful, (keeping in mind the room for freight) because it's a much smaller area to heat or cool for comfort. I used the window shades too, until I got some fabric at Walmart for $1.00 a yard, & some Velcro, and put pieces of Velcro above the windows, & on squares of fabric cut to fit, so now I can screen the whole interior, with no gaps. It doesn't take long to do, plus it's quick to put up & take down, so it's a big improvement for a small investment. The fabric I chose is semisheer, so I can see out, but you can't see in, which is nice.