HELP!:heat and humidity problems

[Bard]

I am very new to this site and not too clear on how to use it to best advantage. I posted part of what follows on another thread and have received no responses for 3 days. I am very discouraged and in need of advise. In addition the problem is more serious than I thought at the time. Some background: I have just completed an orchid growing case 18w x 42H x 35W. It has a humidity tray on the bottom and a 24" 4 tube t5 fixture on top ( 8000 lumens) the back wall and right hand side wall are solid plastic board painted off white while the front and left end are 1/4 plexi, The front panels are on sliding tracks for access,. Ventilation is provided by 6 - 6"x1/2" ports just above the hum. tray and 4 small doors in the top that can be adjusted ( no fans yet). The combination of bottom ports and top vents give a chimney effect and provide a constant and adjustable updraft. This arrangement ,sans fans, works very well in my first case but, in the new, bigger case, I am having trouble achieving the humidity levels I want:60-80% and the heat from the lights is excessive. It burned the leaves on a catt. 3" away and the temp exceeds 82f 16" below the bulbs. On the humidity front, noting that some orchidariums use an aquarium bubbler and air pump, I added an air pump and a 30" of perforated bubbler pipe but it made very little difference, perhaps 10-15% RH improvement. I have also considered a small muffin fan mounted just above the Hum. tray to speed evaporation. Perhaps there is a better option or things will improve if I can draw off the heat, but I would prefer to avoid a humidifier or mister. Interestingly my first case (see photo)is identical in design but only 15" x 15" x 22" and maintains 70% RH at 70f most of the time. Being too small for more, it only has 18 watts of light so heat is not a problem. Fearing more damage to my plants, I have emptied the new case, cramming all the occupants in the old case or onto the windowsill. The case stands ready for badly needed modification but of what sort? Some of the things I have considered are a sheet of glass below the lights but that will cut the light and I only have 8000 lumens, a fan or fans near the top vent doors to increase circulation and pull off some of the heat. Obviously several variables are at work and I really need help sorting them out. Otherwise I will just continue to shoot in the dark, wasting money on things that don't work and getting more and more frustrated. Your thoughts will be deeply appreciated. PS:I tried twice to add photos but they are gone when I revisit the site.