If your attic hatch isn't sealed, it's an escape hatch for heating, cooling and the hard-earned money spent on higher utility bills to pay for both.
Attic hatches are often under the radar when it comes to eliminating sources of energy loss in your home. It's not uncommon to find homeowners who have upgraded attic insulation yet neglected this gaping energy hole that allows heat to escape your living spaces in winter and invade in summer. When a typical attic hatch isn't properly sealed, the hatch alone can lose more energy than the entire ceiling.
With the new changes in the building codes, homes are being retrofitted and built much tighter, trapping moisture inside the house. Any air leakage can cause excessive moisture build-up in the attic causing a condition called "Attic Rain". Around the hatch is also a common area for mould to develop as the moisture from the interior air frosts and condenses around both the hatch and the housing around the lid.
An attic hatch leaks energy in two ways: Direct air leaks around the trim and by conduction through the thin plywood board or drywall material the hatch is made of.
To ensure that your attic hatch is well insulated and has an airtight seal, there should be insulation (rigid foam board insulation is ideal) on top of the attic hatch door, as well as, weatherstripping (generally closed-cell foam tape) on the wood trim lip that the door closes or rests against. The gap between the trim that the hatch door rests against and the ceiling (or insulation-stop material) should be well sealed for airtightness. Consider adding a latch similar to sliding window latches to keep the hatch tightly in place.