Joseph Meehan wrote:
Mike O. wrote:

About two years ago we moved into a 35 year old house. The furnace
was replace by the previous owners and is about 10 years old (92+
Rheem). The ductwork appears to be original (except for a few pieces
around the furnace)
A problem we've had last year (and this year too), is that when the
weather cools down, the upstairs is about 5-7 degrees cooler than the
downstairs. Partially closing the downstairs registers helps some,
but I don't want to close too much and reduce the airflow through the
furnace to a level that will cause problems. I'm looking for a
solution to help the heat make it to the upstairs, without causing
problems with the furnace.
snip
It is rather unusual that the upstairs would be too cool. I might also
suggest that the distribution problem may be more of a return problem than
supply.

We had the same problem in our home, I partially closed most of the
registers over the course of a week to see if things changed. They did
somewhat (though I do like the sleeping areas cooler). After I made sure
that nothing was in the way of my return area (it's in a closet, the mrs
put a laundry basket in front of it), the temps came close to balancing
out.