R-values can be added up. Even an air film on the surface has insulation value. All materials have the same R-value. Insulation can be moved from one place to another. Enclosed dead air space between materials has insulation value.
Reflective materials can work like insulation by reflecting heat away.
Movable insulation works best covering glass. Movable insulation is always electrically operated. For movable insulation to be effective, it must fit tightly in the glazed opening. Find materials to build an insulated curtain and an insulated shutter. Then design ways of putting the material together to cover a window.