“Thermally Active Surfaces in Architecture” is a helpful resource for understanding the ways in which water-based heating and cooling systems outperform air based systems in most cases. The argument is clear that the density of water makes it far superior at channeling energy.
The only issue left unaddressed is how thermally active surfaces can be integrated into existing structures in an efficient and cost-effective way. Most of the examples shown in the book have been designed into the structure from the beginning. The argument seems to be that at some point in the future, all new buildings can use this technology if we begin now.
The trouble is that the existing building stock, in cities specifically, lasts for centuries. The final example in the book is one in which an existing modern building was retrofitted with ceiling mounted radiant cooling units. Given the slow rate of turn-over in the existing building stock, retrofitting existing spaces seems to have the most potential for growth. Who wouldn’t want to lower their summer cooling bill and get rid of those ugly window units!