The contractor will be building a 30' x 31' workshop, finished on the outside but with a bare interior. I'm currently planning on using 6" recessed cans with LED retro-fit units. What are the guidelines for lighting? The shop will have 1 car garage door (normally closed) and two 3'x6' windows pn the street wall (HOA requirement) so it will be relatively dark. How many lumens should I need? Thanks.