I want to insulate my walkout basement foundation (poured concrete). I live in Ilinois with heavy sun on the foundation in the summer and cold wind off a lake in the winter.  I’m having some more grading done on the back of the lot, so a portion of the side wall will have 18″ of new backfill/topsoil pushed up against it. I thought I’d add 2″ of polystyrene to the exterior before the grading is done. I went to the archives to see about leaving draining space/channel. it seems like the space defeats the purpose of the insulation and I wanted to see if its ok to ‘close’ the top of the panels (below a flashing) to prevent water from getting in and to ‘trap’ warmed air. But while in the archives  but note that most contributors seem to prefer insulating the inside walls. I don’t need (nor particularly desire) finished basement walls, I just want to insulate (and add some outside framing for ”storm’  door and basement windows). So the questions are:

A. If I go the exterior insulation route

Is a weep space necessary? If it is, can I just glue vertical thin strips of styrene behind the 2″ pannel to make that space? Do I need to use a insect mesh at the top and bottom? And can I seal off the top of the panels to keep water out of the weep space (and presumably warmer air in)?

B. Should I go inside instead of out with the insulation?

Outside would keep the summer sun off the ‘thermal mass’ and I’d just cover the styrene with the new paints they have made for that purpose. I’d box the 16″ windows with a frame and a homemade storm window. I’d do the same with the 32″ door along with putting in an insulated door (its a panel wood door now). I would get the larger windows replaced later). But I’d have to worry about insects getting behind the panels(?)

Inside I’d have to worry about condensation and framing over the styrene (or whatever I decide to use). And I’d worry IF it ever gets wet (I haven’t had water since I regraded the front of the lot. a couple of years ago…but we did have water seep in before then). And I’d lose floor space (though minor).

Thanks.

Jeff