Is the foundation under the addition an outside vented crawl space, and is it fully closed in with CMU (block) stem walls? How did you access the foundation to add the insulation? What exactly did you add, along the stem walls, the rim joists, or floor joists?

The better situation for any crawl space next to a basement is to remove more of the CMUs of the old house wall to provide an opening, not just to allow the basement air into the crawlspace, but to provide the code required access of 16"x24". Then your crawl needs to be unvented to the outside and will then feed off of the basement air temp and movement.

Interesting. Yes to your first sentence. The is a window of required size. As far as I know it had the insulation board along blocks and he add fiberglass insulation to joists and duct work. Thanks for input. That’s something to think about.