I have a problem with the amount of air comming from the register in my master bathroom, causing it to be fairly cold in there in the winter. The room is ~5'x8' has a 22x42" window, has 2 outside walls, ceiling has about 10-14" of blown in insulation. I have done a bunch of investigating and am fairly sure why the airflow is so poor. The 5" ductwork is the longest run the the house by about 1/3rd and there are at least twice the about of 90's as any other run (10), and lastly there is a large "dent" in the line about 3' before the register where the duct squeezes past the toilet drain. I have the damper open all the way and have tried installing a booster fan, the booster fan made almost no difference.
Anyone have any ideas on how to increase airflow, the basement is still unfinished, and i can access all the ductwork except the last ~7 feet where is goes under the bathroom floor.
Would increasing the duct size to 6" help at all or would the last 7 feet of 5" (plus the dent) make this a wasted effort?