For those of you who are interested in some recent data and thoughtful perspective on the relationship between sustainable design and productivity: Studies Relate IAQ and Productivity - Facilities Management Insights
In addition, LEED for Existing Buildings (LEED-EB) has several Credits that relate directly to this issue:
EQ Credit 4.1, Documenting Productivity Impacts, Absenteeism & Healthcare Impacts
EQ Credit 4.2, Documenting Productivity Impacts, Other Impacts
These Credits were developed to encourage building owners to collect productivity data, which will add to our knowledge bank and provide a more accurate and current picture of the benefits of sustainability.