We have relatively new high efficiency gas furnaces that feed into 100
year old ductwork.
In particular, our 2 third floor bedrooms are fed off the same 9" riser
that feed the 2nd floor bedrooms underneath it. As a result, there is
much less heat reaching the third floor than the 2nd floor.
Even adjusting the dampers at the takeoffs to the bedrooms has only
limited effect, since the airflow is just not powerful enough 3 floors
So, I am wondering whether someone makes a booster blower that would sit
just below the 3rd floor vent grill and would not require ripping up the
walls, ceilings, or floors to install.
Note I know they make inline fans that it into the duct itself, but that
would seem to require breaking into the wall to access the duct. I want
something that would sit right underneath the vent grill.