Our return vent for our hvac is right outside the master bedroom. The master bedroom gets very little airflow with the door shut.
It was recommended that we add secondary return duct in the master bedroom to combat the high static pressure that the house is under.
I have a question though, would it be beneficial to put a vent in the wall between the master bedroom and living room to help ventilate air in and out of the room so there is not as much pressure in the master bedroom?
Yes, adding a transfer grille or jump duct will be the easiest and most effective solution. It can be done in a way to minimize transfer of sound between rooms (see links below). Adding a return to the master bedroom doesn't guarantee that the supply/return to the master bedroom will become balanced—the resulting pressure may still be positive or even negative with respect to the rest of the house.
Assuming the high static pressure is proportionately on the return side, your best solution for better Master BR flow is the new return. Siting the return across the room (from the supply, if possible) will help.
If you are still having high static on return, look at the existing return duct covers. Older houses can have less aerodynamic (painting, denting) covers. Replacing with newer ones can help.
The vent between the rooms would be less useful AFA static pressure, as the ducts are the main conveyors of the airflow/pressure.
Add the return in the room on a side opposite of your positive pressure vents.
If you just want a quick/easy fix, the opening through the walls should be helpful so long as the existing vent is not along the same wall.
If this system is one of many, and its positive pressure vents are all in rooms with doors I highly suggest closing the central return, and adding a return to each room, and putting a damper in each supply duct for fine tuning the flow. I have done this in my last two houses, and the comfort difference in the rooms is outstanding. I imagine this is more efficient as well, since you are likely keeping these rooms cooled/heated while sleeping and not loosing temp controlled air to the central area that is not in use. Make sure your thermostat is in one of these rooms, or move it there if not; preferably to the master.
Easiest solution: move your thermostat to the master bedroom as well and you will always have the temp you want in your room. You may freeze or roast others, and it will cost you more in utility consumption, but it will be easy and get the desired result.
I've seen new construction adding a pair of return grilles to each side of a wall separating a room from the return vent. This gives a path for air to flow. If possible, put the return grilles at the same height as the return vent itself (near the ceiling on upper floors and near the floor on lower levels). I'd also recommend angling the slats in the grille so you cannot see into the wall (angled up for ceiling returns and down for floor returns). And for a bedroom, consider a location that minimizes noises heard on either side of the wall, for privacy.
