soil Cold soil in a warm room?

I have a couple peat pots that I started some seedlings in. They're in a room that has an ambient temp of 70°-72°f  but the soil is 10 degrees cooler. How can this be? Is it an evaporative cooling effect? 
I wrapped one with aluminum foil and it helped a little but still not up to room temp.  At the moment, checking with a digital thermometer the room temp is 72°, the pot wrapped in aluminum is 66° and the bare pot is 62° measured in the center of the pots. 
I'll be moving them to a heating mat for now, but would love to know whats going on with the temps.
Thanks, Dan

Evaporation cooling or conduction cooling to the floor or other surface.
Conduction will be more on stone, cement or marble counters or floors. This can be countered with something as simple as a folded newspaper.