Efficiency and Building Envelope

American society is obsessed with measurement: Superbowl viewership rates, year-to-date flux of the Dow Jones, the body mass index of celebrities.

Ideally, facility executives are equally obsessed with their own metrics: occupancy rates, office churn and energy consumption. For the latter, it is relatively simple to take stock of the performance of systems within a building. But how does one apply efficiency metrics to the building envelope? How does one measure performance?