I have a 15 x 15 finished room in my basement that stays a lot colder than the rest of the basement. It has 2 supply ducts{ in the ceiling} in it that have weak airflow and no cold air return. This room is as far as possible from the 90 plus furnace. The main room of the basement has several supply registers and 1 large cold air return in the wall that separates the furnace room from the main room. Over the weekend I decided to install a cold air return in this bedroom to se if it would help to circulate the air. I utilized 2 wall cavities as the chase{ each is approx 15" wide} and put the grille down around the floor. Each cavity has a 6" flexible duct which connects the chase to the cold air return,each duct is approx 3' long.I did not use larger ducting because of space constraints. Each duct runs from the chase across the bottom of the return duct and loops approx. 180 degrees before connecting to the return duct. The flex ducts are not kinked as far as I can tell. I am getting very little, if any, draw through the new return and am puzzled as to why? When I checked the rest of the cold air returns in the house with a flame, the flame was pulled in towards the return,but not on this new one. The new return is connected to the main cold air return which serves another room upstairs,that duct pulls air without a problem so I know that the return system itself is working. I am guessing that either the 6" ducts are too small or the 180 degree loop has something to do with the problem? Any suggestions would be appreciated.