I think he means it seriously

Hal Foster on Global Style.

In the discourse around Piano lightness is driven by historical necessity as well as technological advance. Buchanan offers a fanciful schema of an architectural Geist that passed from the heavy forms of ancient Mesopotamia and Egypt (ziggurats and pyramids), through the ‘colonnaded edifices’ of classical ‘Mediterranean cultures’, to the abstract ‘grid’ of modern ‘Atlantic culture’, ‘in which nature is enmeshed by the grasp of reason and technology’, and on to a ‘Pacific cultural ecology’ where, in the hands of designers like Piano, ‘the lines of the grid will etherealise into intangible conduits of energy and information, or take tactile biomorphic form.’ For his part Piano states simply that the Pacific is ‘a culture of lightness’, and that he prefers it: ‘Although I grew up in Europe, I feel much closer to the Pacific, where lightness, or the wind, is much more durable than stone.’

Perhaps this notion of a ‘light modernity’ must also be viewed dialectically, countered, say, by the less sanguine notions of a ‘liquid modernity’ and a ‘second modernity’ proposed by the sociologists Zygmunt Bauman and Ulrich Beck respectively. For Bauman modernity is now ‘liquid’ because present flows of capital seem able to carry almost anything along with them (maybe not yet ‘all that is solid melts into air,’ but closer all the time).