What is the difference in energy consumption of hinged and sliding door display coole

I have been asked to provide some input to a client that is looking to reduce his energy consumption through a number of his stores.

One area is with his glass door coolers, at present he has all hinged doors, which lead to cold spill and more load being required.

Does anybody know if this comparison has ever been checked out in a lab etc or if there is a report on this?

If anyone knows I would appreciate it.

Cheers

SM

if he's that worried about losing cold air out of his coolers,why not fit a door switch to stop the evap fans.have him fit energy efficient lights,and adjust he timeclock on his sign