Thanks for all the Great Replies!! No, the house has not been rented
yet so the prospective renters' allergies are not the issue. The
ductwork is aluminum...and the HVAC people I have spoken to feel that
my brother in laws needs to get a life in regards to the "moisture in
the walls" problem. The air return may be more of an issue. There are
three vertical shafts extending into the upstairs floor; one exposed
in the kitchen: one hidden in a dining room closet and one inside a
wall next to the front chimney in the parlor. The only return appears
to be in the foyer on the first floor. Our other rental house came
with A/C but also does not have an upstairs return...the A/C seems to
work OK with ceiling fans on upstairs. Both houses are circa 1890.
Any more suggestions?

In other news...sister and BIL put in two windows yesterday...one an
inch lower than the other.

They're leaving today. :-)

Deano