I have a recently built house and have noticed something that I’m not sure is an issue but would really appreciate some expertise. Our first and second floors are on different HVAC systems. On the second floor, where most of the bedrooms are located, each bedroom has at least two supply register and one return register. When the HVAC fan is energized and the bedroom doors are closed, I can feel a significant amount of air coming through the undercut below the bedroom door.

That tells me that the return has insufficient capacity relative to the supply. Is this something I should worry about? I’m going to be doing some additional duct work this winter and could add an additional return if needed but only want to do so if I need to.

Many thanks for any advice.