ᐅ Insulating the Roof Above the Upper Floor with Loose-Fill EPS

Hello everyone,

My house was built in 1969, and I have insulated the attic and the ceiling of the upper floor with glass wool, which has dramatically reduced the heating costs. Now I want to continue insulation in the upper floor (two bedrooms and a walk-in closet), but due to the effort involved, only internal insulation is possible. The construction of the non-windproof pitched roof, which ends at the floor of the upper level, is built as follows: roof tiles, rafters, and drywall panels as the interior surface.

I plan to screw beams or stiffening profiles onto the walls (42cm (17 inches) thick) and the floor in order to create cavities 14cm (5.5 inches) deep without putting any load on the existing drywall panels. These cavities would be filled with EPS beads and then covered again with drywall panels.

Can I do it this way, and will it be effective? Is the risk of mold very high? Should I install a vapor barrier somewhere?

I would be very grateful for any constructive suggestions, advice, or warnings!

I would advise you to use blown-in cellulose insulation instead of EPS beads. I used EPS myself, and they were blown out by the wind. It was a terrible experience for me.