I know. But injectable foam insulation usually going into empty walls. I already have butted fiberglass in there. I don't think it's viable to make laparoscopi

I know. But injectable foam insulation usually going into empty walls. I already have butted fiberglass in there. I don't think it's viable to make laparoscopic wall surgery to remove fiberglass . I did a quick google, and looks like you can do injectable foam over fiberglass. But I am not sure how much R it will add, but I am sure that for cost of of injectable foam + wall repair, I can get another hvac and run it for next 10 years... I did consider recently to double walls on sunny side of the house with few layers of foil backed foam boards.