Insulating a split-level attic space
I live in the NE USA and have a uniquely designed structure called a colonial tri-level. It is a split-level home with the walk-in attic space in the rear half of the house above and adjacent to two bedrooms. The attic extends above the adjacent bedroom to an attic crawl-space which extends the length of the house. I have insulated crawl space to R-40 with fiberglass batts perpendicular to each other.
The walk-in attic space has 2x6 joists above the bedroom that are insulated with fiberglass and plywood sheets creating the floor. This only allows for R-19 and the bedroom below is always cold. I am thinking of adding another layer of insulation by adding 2x6's perpendicular to the existing floor and adding another layer of R-19. I will lose some space but the trade-off is worth it.
The roof is supported by 2x6 spaced 14-16 inches apart. Can this space be spray-foamed for additonal R-value? Or is there another option for increasing R-value. There aren't any vented soffits anywhere in the attic. There are ridge vents at each end of the attic and a vent from the upper bedroom to the crawl space. The access is a 24" door from the hall.
Any thoughts or questions would be appreciated.