So your attic has no windows, no fresh air in-take and no way to exhaust? ... We need a little more info, what are you working with before we can really recommend anything. There's additives, like Silica Blast or Rhino Skin that'll help plants handle temps up to ~100, ~105 you start to push it.. ~107, the plants will stroke more than likely.. two temperature point difference is no bueno..
When you add an element like being outside of the desirable temp range, you create other elements as well..