architectural case studies which are aiming to create a relaxing,
destressing environment?

Don't know if this is in the direction you want, as it might not be
case study like enough:

Christopher Alexander, 1977, A Pattern Language; The Nature of Order:
An Essay on the Art of Building and the Nature of the Universe (Center
for Environmental Structure)
(mentioned in Wired, Mar 2004, p.64, with a summarized list of the
author's findings)

It seems to be a classic work on aesthetic dimensions of architecture
and it mentions 15 characteristics or factors in pleasing
architecture.

something to start with, but just my quick 2 cents.