I'm building some stackable enclosures and I'm goin to have led down lights in each there going to 1800mm long with only the back part of the space where the downlight a are going being open. Just wondering what clearance I should leave above the doe lights and whether I should put some vents or/and a fan in there so to take away some of the hot air ??? The downlight with globe it 100mm.. Maybe an electrician can help me ?? I've attached a the design I want the area I'm talking is marked 150 but still undecided.