Has any one seen anything like this:-

I have a coldroom-with a pitched roof. The evaporators are located at the bottom of the pitch as it were. They have louvers front and back which close on defrost for some reason! has anyone ever heard of this before!

Because of the louvers fitted to standard evaps we are having problems, airflow related i think, maintaining temperature. I would like to get rid of them. Does any one know any reason why not >?