Mikepier wrote:
Lately I've noticed a problem in my living room floor in that the wood
is buckling or crowning a bit with gaps between the boards directly
above where there is an HVAC duct running underneath between the floor
joists( about 10 feet length total). I think it has gotten worse this
past year because recently I finished my basement and closed the
ceiling with sheetrock, so I'm guessing all the heat from the duct is
concentrated upward towards the floor, although I thought wood shrinks
when its warm and dry instead of expand. Is there an easy fix for
this? Can it be hammered down with a 2X4 and hammer?

An uneducated guess would be that the wood floor expands due to the heat
and insufficient room left around the flooring for expansion. Wood
furniture, usually with some unfinished surface, expands and contracts
because it can absorb moisture from air. Without a moisture difference,
there is still some movement with sufficient temp change. Since you
associate the crowning with closing up the heat duct, seems the answer
lies either in opening ceiling and insulating duct, or ripping up
baseboards and adjusting perimeter of flooring. Got some pix? How much
above the level flooring does the crowning go?