It may depend upon what chassis you have.
The 2005 Ford E450 chassis under our Class C has a very thick insulated cab floor (maybe done by Winnebago?) PLUS ... Ford's air conditioning controls allow you to set the cold air to come out down below aimed at the cab floor and your feet (instead of the usual outlets aimed about chest-high).
I don't think many Ford E350/E450-based Class C owners realize this, but of course it makes all the difference in the world in keeping the cab floor cool. We discovered this capability by accident after owning our Class C for awhile.