p>I wouldn't go so far as saying it was a 'terrible' idea, but I don't think it will do what you hope it will. A 3-inch cavity wouldn't help it dry out in anyway since the only direction it can dry is inwards and that wouldn't change by leaving a space. It's great that you have insulation on the exterior, along with reducing heat loss that will reduce the wetting of the concrete, but it will still likely have an endless source of moisture unless it is protected underneath the footing as well, which I doubt.</p> <p>Myself I would prefer to have a membrane against the interior of the concrete wall to prevent the concrete from drying inwards. And I would either move the stud wall against it and enlarge the space a bit, or, I would use that space to add some rigid insulation (which itself will act to slow or stop the inward migration of moisture. Here is our page on <a href="/guides/2268/best-practices-for-basement-insulation-in-new-home-construction/" target="_blank">basement finishing</a> that may help. </p