Air-seal and insulate your attic hatch or pull-down stairs
Added
Treat the attic access like an exterior door. Add wood trim if needed, install foam weatherstripping so the hatch or stairs seal when closed, and latch it so the gasket compresses. On the attic side, attach rigid foam or batt insulation that roughly matches the attic R-value, and build an insulation dam if loose-fill insulation falls through the opening.
The result
Result: PNNL Building America: openings used for attic access should be air-sealed and insulated so the attic stays behind a continuous air barrier, which helps energy efficiency and helps prevent moisture problems in the attic.
Source
PNNL Building America Solution Center: Air Seal and Insulate Attic Access (opens the original source in a new tab). Check it for the latest numbers before you act.