In 2011, the Danish Energy Agency initiated a study into ventilation solutions for the retrofit of schools to identify the most promising technologies. The reason was an increasing awareness that the ability of school children to absorb, adapt and use knowledge was affected negatively by inadequate ventilation rates. This paper presents an output of this study. A method for evaluation of the ventilation systems is proposed. The method consists of three categories with a clear separation to create a scoring board that facilitates transparent and unbiased evaluation. The method was applied in an analysis of ventilation solutions in schools and the finding was that centralized or decentralized balanced mechanical ventilation activated by CO2 and temperature sensors in the individual classrooms has the highest score and has the best market maturity. Other solutions are possible but unacceptable performance on some performance issues thus has to be accepted. Furthermore, a set of design rules for ventilation solutions in the case of school retrofit is presented. The design rules require an analysis of the building typology before the best solution can be chosen for a specific school.