Sealing an attic ladder is crucial to prevent drafts, heat loss, and dust from entering your living space. Apply weatherstripping along the edges of the attic door to create a tight seal when the door is closed. Add insulation around the attic opening. This can be in the form of a foam box or batts of insulation. Use caulk to seal any gaps or cracks in the attic door frame to prevent air leaks. Install a door sweep at the bottom of the attic door to seal the gap between the door and the floor.