I have a crawl space between two floors in my place (the first and second floors). The crawl space is about 3.5 ft high. The spaces above and below the crawl space are heated/cooled finished living spaces. The crawl space itself does not appear to be vented but it is definitely cooler in there in the winter and hotter in the summer than the finished areas.
The top part of the crawl space (under the floor of the 2nd floor) is insulated as would be expected. However, the bottom part of the crawl space (above the ceiling of the first floor) is not insulated at all and the first floor seems colder than it should be in the winter, particularly for the two months or so in Virginia (where I live) when it is very cold (I don't notice the difference too much in the summer).
Common sense tells me that I should put down insulation batts between the joists in the bottom part of the crawl space (above the ceiling of the first floor)--it seems that the cool air from the crawl space is descending down into the 1st floor and the heated air in the 1st floor is transferring up, making the 1st floor seem colder than it should be.
A few questions: Is there a reason why the bottom part of the crawl space wouldn't be insulated (the place was built in 1990 and we have a pretty engaged building codes/compliance section in our city)? Should I insulate the bottom part of the crawl space? What would be the recommended R value and should there be a vapor barrier and which way should it face (up toward the crawl space or down toward the 1st floor ceiling)? I've found a lot of good information about insulating basement crawl spaces and insulating ceilings in general, but no good info about insulating this inter-floor crawl space situation. Thanks.