I own a 1950's split level in PA. The house has a crawl space beneath the entire first floor. Half of the crawl space is original to house and has dirt floor. The other half was built as part of an addition and has a cement floor. In addition, the house has forced hot air and there is a lot of ductwork running between the joists in the crawl space.
I've read a lot of other posts regarding this subject on TOH but I'm still not sure if I should insulate the walls or the floor. Based on what I've read it seems like I should insulate the floor but the ductwork would prevent me from getting good coverage. That leads me to believe that I should insulate the walls and put down 6 mil plastic on the dirt floor.
As for ventilation, there is an old drafty window at one end of the crawl space and a small door to the laundry room at the other end. Nothing else other than that.
Canuk, you seem to have a lot of expertise in this area. Any suggestions?