As I recall, the comment was about a spray on insulation that becomes itself the new inner wall surface of the building. I think the "tennis ball" part was partly inspired because it was a small geodesic structure. I'll see if I can track down the source. Thanks for all the comments, everyone.

Might want to keep an eye on those timbers that have foam sprayed on them: my engineer tells me it causes them to rot. One house he inspected at rotted every timber with foam on it by the time it was 5 years old! And that was in Fairbanks AK, which is a very dry environment (and cold! -18 here right now...going to be very hard to get those 'net zero' buildings here). I suppose you could keep the moisture out with proper vapor barrier, but it is still taking a chance. Of course there is a place here that is made of *all* foam (between Fairbanks and Anchorage), but that turned out to be a big mistake because they could never use it due to the outgassing of formaldahyde--even after 20 years it is still a problem.