Given the implication of designing Net Zero Energy Buildings (NZEBs), which involves complex passive and active design strategies, the use of computational automated optimization techniques is becoming more essential. Therefore, this structured interviews aims to assess gaps, needs and problems considering the integration of optimization techniques to support the design of NZEBs. This work is part of the International Energy Agency (IEA) Task 40: Towards Net Zero Energy Buildings Subtask B. The objective of this report is to gain an understanding of how experts currently use optimization tools, which tools they use, the major limitations they have encountered, and their vision for the future of optimization of Net Zero Energy Buildings. With this information disseminated, it is anticipated that soft ware developers will be better informed of the needs of building design processionals. A qualitative study design was employed, using semi structured interviews. Optimization experts working in academia and practice were recruited. The participants were identified from the IBPSA Conference Proceedings between 1995 and 2010. A sampling framework was developed to include experts in the study from Europe and North America. These groups represented the range of possible optimization users, from researchers and designers considered optimization in the design of net zero or high performance buildings. A list of potential optimization experts was created and circulated between the IEA Task 40 Subtask members. Also every interviewed expert was asked to revise the list and add any potential candidate to be interviewed.