I have an kitchen addition to my house that's about 2 years old. It is built over a 3.5' crawl space: vapor barrier & gravel floor, rigid blue board insulation on the interior of the foundation wall, batt insulation between the band boards. We have laminate flooring in the kitchen area and it feels cold every winter. It is an unvented basement with a couple small (32 x 24) openings to my heated basement. There are ducts and plumbing running throughout the crawl space. Would it be advisable to also put batt insulation between all the floor joists? Or is there something else I should consider?

I would think a tight, insulated crawl space would stay warm enough to keep your floor warm. I meticulously sealed my crawl space caulking between the foundation and plate and top and bottom of the band joist. I also sealed up around the pipes and wires where they went through the wall or the floor above. Warm, moist air can follow pipes and wire clear up to the attic and create condensation problems. My crawl space stays about 60 degrees year around. That leaves the hardwood floor in our family room nice an warm.

If you are losing a lot of heat out of the crawl space, and insulate floor rather than stopping the heat loss, you could end up with frozen pipes the next spell of weather like the last week or 2 in much of the nation. The plumbing forum has a rash of no water posts.

If you insulate the interior wall of your foundation, make sure it's a 100% seal otherwise it will not do you any good. All holes will have to be blocked off.