I have a home built in 1965 that I purchased in Calif. a year and a half ago. I am sure none of the exterior walls are insulated because I can feel the cold through the walls. I am considering the spray foam method, but, having read your comment concerning the process, and you have recommended to others the blown cellulose method for DIY, I am interested in what is required to do it. I imagine that only the exterior walls need this treatment so how is it DIY friendly vs having a professional do it? I am 100% for DIY.