Can foam be pumped into existing walls?
There are some companies that have tried to claim success with this but it is our experience that foam needs to be installed into open wall cavities. For good reasons:
The CCMC certified foams on the market today are spray formulations and not pour. They rise and set in seconds not minutes. Also when filling an enclosed wall the foam will take the path of least resistance and this can mean bowing the walls out instead of rising up. Also many older homes that this process seems appealing to have fire blocking at intervals and thefore making it difficult to precisely install the needed insulation.