From dirt to doorknobs
It’s a rare attic or crawlspace where we see no evidence of these nasty critters. It seems like they climb, swim, dig, or chew their way into our houses no matter what we do. One homeowner complained of rats that ate the fruit out of their dining table centerpiece!
It’s bad enough that they get into our attics and crawlspaces, worse yet is what they leave behind. Proteins in their urine are potent allergens and become airborne when dry. Their urine and feces can contain hantavirus, a group of deadly virus that can be aerosolized and transmitted through air movement (more on hantavirus).
In the average house ducts leak at least 30%, and the building “shell” leaks at least 100% more than what’s required for adequate ventilation (data). If the leaky ducts run through the attic or crawlspace, they can directly vacuum up rat leavings and deliver it into each room of the house. If they don’t vacuum it up directly, they can depressurize the house, causing the house itself to suck it in through all the little holes and cracks between the attic or crawlspace and the house.
In a typical building performance project that involves rodent infestation, we remove all contaminated materials and neutralize soiled surfaces. Then we reduce duct leakage and eliminate air infiltration between the attic or crawlspace and the living space. Even if the rats eventually get back in, the bad stuff stays in the attic or crawlspace, not in the bedrooms.