It is proposed in Dutch and EU policy to be carbon neutral by 2050 to mitigate climate change. Hence, it is important to improve the energy efficiency in existing real estate as the built environment is responsible for 16% of total energy use in The Netherlands. Net-zero energy building (NZEB) retrofit concepts have been developed and are being tested as one promising solution. However, the NZEB retrofit industry is still in its infancy, and upscaling these concepts faces difficulties. Influences for upscaling were investigated by doing case-study research substantiated by two frameworks from the transition studies field: the socio-technical system analysis and innovation niche analysis. The two frameworks were adopted to identify the origin of the upscaling barriers and understand the development of the NZEB high-rise retrofit niche. A list of 30 upscaling barriers, barrier solutions, and seven upscaling drivers were identified through literature review and interviews with industry professionals from the two project cases. The barriers from the literature review and case study were compared and double-checked. Furthermore, the management quality of the important innovation-niche building processes were evaluated, and improvements presented. The results of the analyses were then connected to answer what is thwarting upscaling and what can be done to enhance upscaling by presenting strategic recommendations. An upscaling guide for both consortia and government is demonstrated. More specifically, recommendations for developing consortia are: forming complete networks; setting clear and aligned expectations; experimenting with small manageable elements; adding system integration and modularity to the design criteria; and forming new business models and perspectives. Suggestions for policymakers include the following: 1) more experimental space and rule exemptions should be available for NZEB projects; 2) the 70% decision rule for housing associations should be simplified for the NZEB project; 3) updating the energy efficiency fee act (in Dutch: EPV wetgeving) and virtual energy balancing rules are suitable for boosting the upscaling of NZEB high-rise projects; 4) Furthermore, criticism has been provided on the subsidy policy in the Netherlands.