Modern loft access hatches, no matter what material they are made from must meet minimum requirements set down in today's Building Regulations.
Heat loss through an uninsulated loft hatch is far greater that the surrounding ceiling, this can result in mould forming on the surface of the hatch. When the hatch is insulated to the same level as the surrounding ceilings then mould growth will not form.
There are different insulation materials available to insulate the hatch door. 100mm of rigid insulation board is the most popular, this can be glued to the surface of the hatch.
Access hatches must be draught proof to prevent air leakage. A rubber seal or gasket is required between the opening door and the frame. Air leakage can reduce the temperature around the hatch area causing discolouration of the hatch. The hot air leaking into the roof space will have higher moisture content than the air in the roof space. When this occurs condensation will happen which may cause further problems.
To prevent the loft hatch from lifting when external doors are opened a catch can be fitted to the door and the frame.
Factory Produced Access Hatches
A number of manufacturers produce ready made hatches that meet all the requirements. Usually made from PVC or glass fibre, they incorporate rubber caskets and are insulated. Because they are made under factory conditions they have a tight fit between the door and the frame and often incorporate a locking device.
Loft hatches come in standard sizes so that they can be fitted between the ceiling rafters, one of the standard sizes is 680mm x 520mm.