85 WE ENVISION A FUTURE IN WHICH society will routinely consider restoring existing buildings to the performance stan- dards of new ones—whether an existing building is abandoned and forgotten or outdated and underperforming. We hope that, over time, it becomes socially and ﬁnancially unacceptable— even unfashionable—to build a new building when there is an existing building perfectly suited for restoration in the same neighborhood. The pace at which we achieve this aspiration depends on the urgency we show to expand design imperatives beyond mechanical system components to include envelope system components. The quality and performance characteris- tics of a building are fundamentally deﬁned by the quality and performance characteristics of the building envelope, which is often overlooked by the design teams on existing-building projects. Chapter 5: The Building Envelope Holds the Key Someone is sitting in the shade today because someone planted a tree a long time ago. —Warren Buffet Robert P. Sroufe, Craig E. Stevenson, Beth A. Eckenrode, The Power of Existing Buildings : Save Money, Improve Health, and Reduce Environmental Impacts, DOI 10.5822/ 978-1-64283-051-4_6, © 2019 Robert P. Sroufe, Craig E. Stevenson, Beth A. Eckenrode.