Heat distribution in upright racks?

[Tim_Cranwill]

I have several melamine racks with heat tape running up the back. I have found them to be great space and time savers. However, I find that even with the back of the rack insulated with Styrofoam, I get a pretty wide temp range from cage to cage in the same rack. I have found up to 10F difference from the top cage to the bottom cage. I know that heat rises, but this really sucks!

So, I wanted to see what other people have experienced with these racks and what, if anything, you have been able to do to remedy this situation.

Thanks!