In order to get to scale and rapidly decarbonize the energy use of homes, we need information on the performance and costs of potential home upgrade measures. The costs for different performance levels are vital for energy savings and decarbonization program planning and to focus R&D activities on measures that could achieve significant cost reductions. This study obtained data from over 1,700 projects that aimed to achieve advanced levels of energy use and related carbon emissions reductions. In this paper we examine the measures related to air sealing (for both the home building envelope and duct systems) and ventilation and present the relevant cost analysis. The results show that there are challenges to obtaining the envelope leakage levels appropriate for the energy and carbon savings we would like to achieve, that duct leakage reductions can be much greater than those for envelopes. From a cost perspective, envelops leakage can be substantially reduced with additional effort, but duct sealing results depend on parameters other than cost/effort. In addition, provision of adequate ventilation are rare and require additional emphasis or mandated requirements in future programs to ensure that indoor air quality (IAQ) is not compromised in decarbonized, energy efficient homes.