We have spent the last 4 weeks chasing a "skunk" odor. We checked for skunks, we extended all waste vent pipes, we serviced the septic system, we opened the walls in the area that it repeatedly appears. After checking EVERYTHING we found the issue! Please pass this on to anyone else that is experiencing! BATS!! It is Bats! You have to check the interior wall insulation for droppings and for the odor - which can build over time and when the pressure drops outside at night it seems to appear stronger. When you open the walls in the area that this is most prevalent, you have to check the wiring that runs between the walls and that they are sealed, if not you have to seal the openings between the walls with expansive foam. The wires are like a super highway allowing them access into other locations. You will have to remove the old insulation which will have the odor and you may need to replace the drywall. Bleach the areas and let them air out for a few days before you close the space. You also want to check for exterior entry points along the roof into the wall spaces. This is a terrible thing to experience in your home and shakes you to the core. WE are very happy that we found the issue and have resolved it. Good Luck!