When considering insulation retrofits, property limit distances and setbacks make interior insulation of residential homes the only viable option. When pursuing an interior insulation retrofit the potential for brick masonry freeze thaw damage needs to be considered. Studying the impacts of an interior insulation retrofit Pre-World War 2 residential building in Toronto, Ontario, a comparison of the retrofitted building using WUFI against 8 other insulation types was completed to determine if the change of insulation affects the potential for freeze thaw damage. Based on the results of the WUFI analysis the answer would be yes. The insulation type and R value does have an impact brick masonry freeze thaw resistance. However this relationship is general and not linear. The method provided shows that if critical saturation (SCRIT) is known predictive modeling on the impacts of interior insulation on the moisture performance of the brick masonry wall can be used.