Fiberglass batts are 4x cheaper for the R value and can be DIY. Spray foam cannot be easily added to an existing home without a professional coming out. (exce

Fiberglass batts are 4x cheaper for the R value and can be DIY. Spray foam cannot be easily added to an existing home without a professional coming out. (except for the cans used for air sealing gaps. It's essentially a waste of money except for limited applications, which is why you won't find any builders at any price point using spray foam as a primary source of insulation. Spray foam is also a pain if you need to get into wall/ceiling cavities for HVAC/plumbing/electrical repairs/additions.