DerbyDad03 wrote: " all the time? I think not. While
the mail flap is less "leaky" than an open window, it's still an
opening that reduces the R value of the door.

BTW if simply opening your attic stairs causes heat to "blast" into
the attic, you may need to improve the insulation for the opening. "


My attic stair swings UP toward the
opening, and is closed-foam weather
stripped by me. Plus I have 1/2"
styrafoam on the top side of the panel,
beneath the steps, shiny side down.

A lot tighter than you might think. We
might add the foam dome you mentioned.
Thanks for mentioning it.