How do you improve a patio door’s insulation?

Stopping air leaks (seals and proper closing) often does more than adding simple weatherstripping. Better glazing (double or triple depending on the model) and a tighter frame.

Also worth considering

Blinds and curtains help with perceived comfort, but do not replace an airtight opening. We compare lines by width (5′, 6′, 8′) and ENERGY STAR® when it applies.