I do know that squirrels are very destructive, and yes, they will winter up, under your eaves. We have felt paper underneath, and they got, 'inside', and we have oak trees...hence...acorns.
My brother got under there, and pulled on some of the loose felt paper, and got an avalanche of acorns coming down.
They will also climb under your hoods of your vehicles and nest in there, and chew wires, and then your car won't start!
Not to mention, the critters that will start coming around, looking for them. :shock: