Maine Passive House (MPH) has used two different strategies in retrofitting existing homes. One strategy involves adding insulation to the outside of the building; the other strategy is to add insulation to the inside of the building. Most projects involve a mix of the two strategies. Along with added insulation and eliminating thermal bridging, MPH increases air tightness, installs high performing windows and doors, and adds mechanical ventilation systems in their projects. They use Therm and PHPP to help build cost-effective resilient buildings, most of which are insulated with cellulose and local materials. MHP has done two residential retrofits (close to PH standard) and one commercial retrofit. They will use case studies to discuss lessons learned from the field.