I've read the similar posts on this subject, but didn't want to hijack them. We bought our '48 split level about 6 yrs ago. The main floor is over an uninsulated crawl space. The crawl space has two exterior vents, and vented vented doors to a downstairs family room.
When we bought the house the home inspector said not to insulate the crawl space. I cant remember his exact reasoning, but I believe it had to do with the heater needs to pull air in to be efficient. After the first winter without being able to use the downstairs family room, because it was so drafty, I finally put insulation in the vents and on the vented doors. This did help....although still cold.
The main concern is the main floor....it seems cold all the time, so I was thinking I should insulate the floor. From reading the other posts, I'm thinking this will be ok. What size insulation should I use...were in South Eastern, PA. I saw something in one of the other posts about moistue control, should this be a concern in the summer?