Not only do outdoor area rugs look pretty when anchoring a seating area on a porch or deck, they make it more comfortable for barefeet when the hot sun is out.
He goes on to note that the slabs have to be kept perhaps too warm simply to remain comfortable; «A slab maintained at 74 °F (23 °C) will be cooler than an occupant's skin, so barefeet will conduct heat into the slab.»