We never used insulated tarps over our wall tent. Just the regular tarp. We have a good woodstove and been setting this camp up for moose camp and then from December till April in the mountains for sledding and been trapped in a few blizzards/sudden cold snaps. Been almost -40, but it was warm in the tent. The Lamb's Palm Breeze Antifreeze maybe helped a bit.
The regular tarp will hold the heat down.