I wonder why as well. I thought I read somewhere recently that the building was ahead of schedule and under budget. CMIIW. It beckons the
question as to whether value engineering had anything to do with it. Even with a western exposure to sunlight here in Calgary, you can still
get some colossal heat gain coefficients. Perhaps they specified a glass that deals with that effectively, and discovered that the Royal Canadian Mint
couldn't even cover the cost, hence going to more spandrel. I'm just musing, as I don't know enough about the materials they are using. Typically,
for any BIM building design, they would have modelled that in the early design phase.