NE had heaters under the turf when they used grass. I imagine the new field turf is still heated to keep the ground soft rather than like concrete.
The Eagles have heat under their playing surface as well. It's a grass field, but also has artificial strands sewn in to supposedly give the natural grass something to bind to. Whatever the reason, it hasn't worked as the field is pretty much nothing more than painted dirt by season's end. That's what they get for allowing Temple University to play their games on Saturday, and the Birds on Sunday.
