We have an old dryer vent that is no longer in use, but is still on the outside of the house. Due to some regrading, the vent is now below the ground line (but boxed off). This causes obvious problems when it rains heavily and often.
I was thinking of pulling the vent cap off and filling the most of the hole with spray foam, then after curing put an inch or so of mortar on the exterior edge. I'm not too worried about needing to undo this fix (I know the foam can be extremely difficult to remove...)
But I haven't used spray foam before so hoping to get some affirmation so I don't do something dumb.