Check the gap and sealing of doors and Windows.  

See whether the clearance between all kinds of profiles is close, with whether the incision is flush, profile lap of the height difference and so on.  

Generally for pvc folding door, the main part of the consideration is the gap between the door frame, the door lamination and the door plate edge, shutters of various profiles, sealing strip, etc.

As assembled door panels, but also consider the gap between the door panels.Is the flat door but also two door fans in the closed light, etc.