Most builders of high performance homes have given up on fiberglass batts—they are just too hard to fit around wires and pipes, achieving only about 60% of their rated R value.
Blown in materials better fill the cavity, but few are installed to a density that stops air movement.
Spray Polyurethane Foam has some attractive attributes, but is a petro-chemical plastic, highly flammable and with known toxic ingredients.
As typically applied in attics, it may also be allowing moisture into contact with cold roof sheathing risking decay.
Dense Pack Cellulose is by far the most benign and effective insulation available.
Low embodied energy, recycled and recyclable; when treated only with natural borates, highly fire, mold and insect resistant.
Applied at 3 ½ pounds per cubic foot, it stops air, buffers and redistributes moisture — helping to protect the structure from decay.