[shelzmike]

What I mean is you have a mud ring installed, cut out quite tight around the outside using a rotozip. Is mudding in the space between the mudring (caused by it's rounded edges) and the drywall necessary since a faceplate will cover it without issue? (Assuming of course the plate will sit flush to the drywall.)

 

[ServiceCall]

No. Don’t have to

 

[Bud9051]

Hi Mike,
Mud rings were invented long before air sealing became an important step. Unfortunately a mud ring doesn't lend itself to good air sealing along with the box behind it. The plate will cover the cosmetics but any air sealing you can do wouldn't hurt.

Note, there is a debate as to whether air sealing electrical boxes does any good, it does but requires a longer reply.

Bud