Facts:
1) Location: Norfolk, va - considered a mixed climate
2) House: main portion- 1930s balloon framed house with a combo basement AND crawlspace. Recent (unfinished) addition has vented crawlspace (I know, gasp). No insulation in basement or crawlspace to date.
3) Basement ajoins crawlspace so there's currently no partition separating these spaces.
3) Basement serves as a moderately sized workshop/ mechanical area. Crawlspace is home to hvac ducts and air handler. Most ducts run below floor joists.
4) We are NOT in a flood zone, and don't get any water in the basement.
5) Addition space is slated for in-floor radiant heat, staple-up kind so we had planned on putting fiberglass insulation in the (vented) crawlspace joists here.

We have read buildingscience.com articles, and are considering making the crawlspace areas conditioned crawlspaces. (Ie covering walls with rigid foam and fire barrier, floors with poly, and sealing all).

Our problem is what to do with the basement. Currently the basement has lots of mechanicals, workshop tables along the walls. One proposed buildingscience application calls for installing polyiso only on the upper half of the foundation perimeter wall. We have considered doing this, but haven't come across anyone who has ever done this....

Another possability is to punt on going the vented route. In this case, we have considered putting taped polyiso on the floor joists and filling with either fiberglass or cellulose. Joe L at building science recently exposed this application (if you have to go the vented route).

Anything I'm missing???? any thoughts, insight, real life senarios.