Seems like a good option for safety and comfort in the tornado zone.
I’ve been thinking about one.
I live about 25-30 miles from the Texas Gulf Coast.
Hurricane can blow all it wants and not even wake you up.
I don’t know about cooling in the summer though.
Here our humidity is so high I don’t know if just wetting the earth cover would work well enough by itself or if it would lock moisture inside and create a mold covered mess.
For dryer areas and tornado ally they sound great.