Styrofoam has problems as a sealant because it weakens in sunlight, and is weakened by heat, and there are common solvents that can dissolve it. It does fill spaces that can't be reached but needs an outer seal like duct tape to do a better job! read more
Insulating foam sealants are a type of spray polyurethane foam (one component foam) that has insulating, air sealing, and adhesive properties. Insulating foam sealants are available at home improvement stores and come in small cans (typically 12-24 oz.). read more