Yes, if you run your fans horizontally, you can get a little bit of a layering effect. I have a short and temporary 8X12' that has my pleurothalids on the floor, and many warm growers hanging, including my Phals under a section of added shade cloth to lower the light levels for these. Vandas hang at the south end where they get the most light and a lot of warmth during the day. You are going to need to do a very good job of insulating. I also made a coldframe running along the length of the GH, with a lid that automatically opens when it gets hot, which it will in winter, the only time I use the coldframe, and two small holes into the green house, one at each end to keep it from freezing, with a fan the runs the length plugged into the heater thermostat for the main GH, so a pressure differential exists to move the air out one hole and in the next to make sure the coldframe gets some warm air. We get down to 10F here, and the frame gets down to about 38F.
http://www.pbase.com/schnitz/temporary_greenhouse