I'm not sure about plastics specifically and how many of them are recycled into the feedstock for new materials used in retrofits. Certainly, in other kinds of insulation, we see recycled paper products, newsprint boxes and cardboard being used for very environmentally friendly insulation that can be used in walls and attics as well.
There are definitely opportunities to use recycled products in retrofits, but it's not my area of expertise. I'm not sure if Lorrie could add more detail.