Temperature.

A heating mat is specifically designed not to emit much heat - they only generate enough mild heat to warm a bit of soil in a pot for seeds or seedlings so they're not going to do much for the overall temperature of your tent. That being said, it might be worth putting your pots on them, especially if they're in a winter shed because insulated or not, the floor is probably going to be fairly cold and doing so would at least buffer the pot from the cold floor and help keep the roots warmish... The best thing you could probably do is to provide heat for the shed itself although that might not be feasible... but keeping what we call the "lung room" warm will help maintain the heat inside the tent. Good luck!