We have a 2 story house built in 1927. It is heated with forced air gas furnace. THe furnace is only a few years old and in very good condition (just serviced a week ago). The 2nd floor is a converted attic. One of the bedrooms is really cold. We thought we just needed to add insulation to the walls (not very much at all), but I was in the room today while the furnace was on and noticed that barely any air was coming through the vent. And, the little air that was coming through the vent was not warm. The vent in the room next door was blowing strong warm air. What should I do to get warm air to come out of this vent?