When the mercury drops you aren't the only one that wants to come inside.Rats, mice, bugs, squirrels, reptiles, vagrants, bums and all your kids friends want to share your hearth and home. You can't do much about the humans except on an individual basis but something can be done about the rest. The vermin with fur just love the attic/crawlspace. Seal up every opening you can find with spray foam, caulk or even steel wool tucked around gaps. inspect and repair any damaged screens covering openings meant to be ventilated (you know that hole the neighbors cat uses to duck under the house). Do the same for the attic, attics are meant to be ventilated so dont block air vents in the soffit or near the ridgelines. Pipes and wiring are run in the walls and on older houses the holes drilled to facilitate their installation were never sealed. Again here you can use spray foam and caulk to seal holes. When you come out of the attic backtrack and replaced disturbed insulation and add as necessary. Now in a best case scenario you sealed critters out as well as trapped a few inside. The down side of poison is obvious...besides being poisonous to you and pets and family the rats and mice can't get outside to die if you did a good job sealing and will smell pretty rank. For these I recommend traps...traps set right will kill them where they can be safely removed and disposed of. I also recommend the use of a good exterminating service for any bug problems you can't handle since a licensed exterminator has been trained to safely handle the various poisons/agents used to control pests without harming you or your family/pets. Ask to see the credentials, don't settle for Bubbas bug blasters cause they are cheap.