DerbyDad03 wrote:

In either case, a garage door that improves the (1) weather barrier
and/or (2) saves energy in the climate controlled cases, should be
just as eligible as the entry door or windows of the house itself.

Obviously, giving a tax credit for a door on an uninsulated garage
wouldn't make sense.

In my view, neither would an insulated garage door. Even if an attached
garage, what's the R value of 20 feet of dead air? Whatever the insulation
on the door might be, it's got to be negligible in comparison.