What Pixar did with CGI, National Geographic has done with a 16′ x 16′ house and 300 weather balloons. I don’t know whether the creators of UP looked into the possibility of whether balloons really could make a house fly, but apparently the idea wasn’t as far-fetched as I thought when I saw the movie.
According to Wikipedia, “a technical director worked out that in order to make Carl’s house fly, he would require 23 million balloons.” I suppose that would be if they used normal balloons such as one buys for a party. In the movie, the balloons were each about twice Carl’s size (which was pretty small to begin with), and number from 10,927 to 20,622 depending on the scene. The 300 weather balloons used by National Geographic are each 8 feet high.
People can fly with balloons also – and it only takes about 50 to 150, depending on the size. This article is an introduction to cluster balloons. It explains some of the differences from hot air balloons, but doesn’t really get into a direct comparison of the two. I suppose some people like the idea of hanging in a harness rather than sitting in a basket – perhaps more of a feel of really flying rather than being carried.
Personally I’d just as soon stay grounded, but these photos of the flying house are pretty cool.