R values are often used in the marketing of air mattresses or thin foam pads used by backpackers.  There’s no reason to test the Rev Tent for R-value because the Rev Tent sleep system is so thick.  There's a layer of rubberized nylon (the base / case of the tent), then cotton and 4" 10.4cm of dual layer foam, then a quilted mattress cover between you and the ground.  The Rev Tent mattress is much "warmer" (more resistant to transfer the cold from the ground) than any camp sleep pad and much warmer than an air mattress.     

 This goes a long way of saying, the cold ground isn't an issue when sleeping in a Rev Tent.  Focus on staying cozy wrapped in a C6 MuthaTucka Camp Blanket with your feet in a pair of Slooze sleep shoes!