In order to understand the applicability of multidisciplinary design optimization (MDO) to the building design process, a MDO framework, titled Evolutionary Energy Performance Feedback for Design (EEPFD), along with the prototype tool, H.D.S. Beagle, were developed to support designers with the incorporation of partially automated performance feedback during the early stages of design. This paper presents 2 experimental case studies, one from the design profession and the other from a design studio, that evaluate the applicability and impact of EEPFD on the early stage design process. Through these two case studies two different interaction and automation approaches for applying EEPFD are explored as part of the framework validation. Observed benefits, challenges and suggestions of EEPFD’s implementation are then presented and discussed.