Does an undercut door or a transfer opening qualify?
It is clear that some ASHRAE research would be helpful in better defining how to treat an undercut door or a transfer opening.
For example, it seems advisable to further define whether an undercut door or a transfer opening qualifies as a permanent opening between rooms, and if so, how large would it need to be, and how high or low it should be installed.
How to treat an undercut door or a transfer opening, or a parallel ventilation system, really need further exploration.
1 Undercut door
casing using underlayment and flooring as a guide.
Next, undercut door
casings by laying the blade of a handsaw on a scrap of underlayment and horizontally cutting off the bottom of the casing.
4 UNDERCUT doors
casings, jambs and other spots where you can't hide the flooring edge with baseboard or transition pieces.