Remove your existing attic hatch and measure its size.
Seal attic hatch.
Hardware 2 small bungee cords to seal it tight.
Pray that the installer used finish nails and not say ring shank nails.
2 thick foam board 4 8 sheet with an r value of 10 or greater 15 foam weather stripping the wider the better 1 can great stuff foam or similar 1 tube liquid nail or other construction adhesive 8 16 penny nails misc.
The stops provide a wider surface for attaching the weatherstrip and a space to mount hook and eye fasteners.
Apply weather stripping to the door to create a seal.
How to insulate and air seal an attic access hatch.
Sealing the attic hatch or door finish up by sealing the access hatch with self sticking weather stripping.
From inside the attic check for any openings holes or fenestrations into the knee wall surrounding area.
Cut four pieces of polystyrene rigid insulation about 1 2 inch smaller than the dimensions of the hatch.
The insulation will both slow heat loss and add ballast to the hatch to improve the seal at the weatherstripping.
Diy sealing the attic hatch seal trim to ceiling create air tight seal between hatch and trim.
Once you have the materials you can begin to seal and insulate the knee wall access door through these steps.