greenhouse heating up

[cathy]

it hit 100 degrees today and this is just the beginning. i have a 12 x 20 greenhouse with a water wall and floor misters since the water wall does not do what i had hoped. anyway 3 exhaust fans are going full blast opposite the water wall, 3 fans inside circulating the air, shade cloth, aluminet and white styrofoam panels here and there. without cutting out much more light what can i do? roof vent? another fan blowing air straight up from the floor? i have to keep my orchids happy.
cathy in s. texas