For the winter, bundle up in a 0 degree European rated sleeping bag a sleeping bag mat availble at walmart for under 10 dollars will reflect all your body heat back to you. With all the windows and vents closed, the truck's engine off, and the curtains pulled, you will hear very little even if someone is idling his/her truck with a reefer running next to you. Cover the sleeper sunroof with cardboard and tape, take it off when you want to. By the way, this saves fuel too, and the cold air will always seep in in the middle of the night. If you parked anywhere but at a truck stop, you will feel refreshed when you wake up because of the fresh air you breathed when you slept. Have your portable toilet or milk jug handy. If nature calls in the middle of the night it will be quick and back to warm sleeping quickly. ONLY open your sleeping bag enough to get in and out fast and conserve heat. If all else fails, cook dinner or boil water in your portable stove to make your space warm. Do not light fires or burn sterno inside your sleeper(I learned this the hard way).
In the summer, tough it out like a real man. Go without clothes inside your sleeper(no one knows). Drink plenty of water to cool your body and fight fatigue, wire some computer fans to a twelve volt "Marine Deep Cycle" battery, wear light clothing if you must, trade your boots for sneakers. Cover that sleeper window with white painted cardboard etc, etc, etc. Good luck.