Expose the ceiling finish approximately 12" on all sides of the attic access hatch.Cut two pieces (or more) of rigid foam to adhere to the access cover. Size the rigid foam so there is a layer adhered to the access hatch that fits within the opening joist space and there is a layer of foam that fits over top of the ceiling joists on all sides. Adhere weather stripping to the ledge of the access opening on all sides.Install plywood or OSB box around the opening. Size the box so that the top edge is above the additional insulation level. Notch it to fit around joists and other framing and use additional framing to reinforce the box.Replace existing insulation and install additional insulation around the box.
Ensuring a proper air seal
Use latches around the attic hatch perimeter to ensure engagement of the edge gasket.
