Hello all -
This is more a pest in the HVAC system problem (didn't see pest forum, so apologize if I missed it). I have a gas furnace in the basement that feeds to several registers in our single story home. In the last couple months, some nocturnal critter has been scratching furiously beneath a heat register in the furthest (from furnace) part of the house, where the crawl space has least clearance (i.e, the part I can't get to). I popped the register and duct boot was hanging beneath the cutout by a few inches, pulled from the floor. I re-nailed it shut and thought the problem was briefly solved. I also found that a nearby foundation vent had a hole a few inches wide in it, and sprayed foam to seal it.

Nope! The scratching came back at night - but intermittently (1-3x/week). Sounds like something is furiously trying to scrape through the register into the home. Now, little to no heat comes out as well. I believe the critter must have torn some holes in the ductwork based on this. I also cut some hardware cloth and closed the foundation vent again - the critter had scratched/chewed its was through all the foam and the gap was even widened to about 5"across - and left a basement door open at night as an exit.

I know a skunk was living under there this past summer to Fall, possibly making it its den and breeding. Haven't smelled it in last couple months.

Question - does this sound like a skunk (size of hole, nocturnal, known presence)? If so, why would the skunk be obsessed with the duct/heat register? Would they den inside the duct?? Other thought is could be a rat but haven't seen evidence of this...thoughts?

OK - this was quite a rant. Sleepless nights.
Best,
Jamie

(PS-Oakland in SF Bay area)