This reminds me of Buckminster Fuller's cloud 9 concept. His idea was that since volume scales so much more strongly than surface area for a sphere, if you make a larger and larger sphere you will enclose cubed more air for only squared more structure. Build a large enough sphere and heat the enclosed air a couple degrees above ambient and the entire structure would be buoyant, like a soap bubble with human breath in it.

http://en.wikipedia.org/wiki/Cloud_Nine_%28tensegrity_sphere...