Mechanical Engineer?

I am NOT a mechanical engineer. I wish I knew one! Designing the ductwork for my coffee shop sent me to Google again. I spent several hours last night searching for information.

I fell asleep thinking about roof top a/c units, cold air returns and HVAC design.

Photo from Reiner Group,Inc.

I thought would be easy enough to build something like this? I could even hide the batteries for the lighting inside?  This is one I made this morning.  It looks too large, but it's a start.

I found another website with more mechanical information that I will ever need!  

DesignMaster.biz.

I have to go to work now.  Hopefully, I can get my mind on my work and off building air conditioners!