Insulation of any kind on the pulldown stairway face is just kind of a bonous if it happens to be there at all.

Just as your solid wood exterior doors do not have the same R value as the wall system they penetrate, the pulldown stairway is not going to match the R value of the ceiling system it penetrates.

You can get attic stairway covers that are insulated and help to reduce air exchange between the conditioned space and the attic but I have yet to see a builder who will install them. Its just one of those aftermarket things the homeowner has to do on their own.

Here's one option...

Amazon.com: Battic Door Attic Stair Cover With R-7 Insulation Kit, Fits 25" x 54" Attic Stairs. (Please see other listing for 22x54 size): Kitchen & Dining