Insulation and air sealing are two of the most common interventions performed in energy efficiency upgrades, and yet they can introduce many chemicals of concern into buildings. That’s why Healthy Building Network (HBN) teamed up with Energy Efficiency for All (EEFA) and other partner organizations to consider healthier insulation and air sealing materials and how to help encourage their use in multifamily energy efficiency upgrades. This report includes details of HBN’s research on the common chemical content of a range of insulation and sealant materials as well as simple, actionable recommendations to make the best material choices possible. Because hazardous content is not the only consideration when making material choices, also included is HBN’s compilation of relative cost information, performance characteristics, and installation and code considerations. Finally, the report introduces a discussion of policies that may impact material decisions and how to encourage the use of healthier materials in multifamily energy efficiency upgrades.