Quote Originally Posted by beenthere View Post
Low static pressure in the duct permits the air to travel easier in the duct. Since the pressure is lower, it doesn't force out more air then required to the closet supplies.

High static pressure causes the closet supplies to get more air then the rooms need.

Booster fan ,when ducts can't be corrected due to construction.

Improving ducts in an accessable basement ,could lower the static enough to mean that the ducts in the walls are "now" large enough.

Lowering static close to the indoor unit ,makes more available for the farthest runs.