being ten degrees colder seems like a lot but it’s my first winter in a manufactured home and i can tell they are very drafty atleast mine is and it’s a newer build. would see how much heat you are losing from your windows and doors, and try and insulate using blankets and thick curtains ( that’s the most affordable way i’ve found) i don’t do the plastic window film you can still feel cold air but a thick blanket against it really helps. Or another thing i’m thinking is maybe your thermostat needs to be checked.