Lighting up high or low?

[JordonMusser]

http://garagejournal.com/forum/showthread.php?p=2110046#post2110046

New garage build! I have more of the fixtures shown in the first picture.

I am considering using. 2 questions:

1) Since my ceiling is high in the new area, should I mount them on the roof, or hang them lower? I am considering going to the roof with them.

With that said, 2). I want to insulate the roof, and these lights were in a drop ceiling. Can I install them up against the insulation like that (recessed)? I could also mount them flush on the drywall, as I have in the previous area. Not as pretty, but cheap and effective.
My other option is buy a bunch of 4ft T8s from home depot, but these are nice 4 bulb fixtures (much nicer than cheap HD stuff) And would like to use them if I can.

 

[Stuart in MN]

How high is high? Those troffer lights are designed to be installed at a nominal 8 feet above the floor, mounting them higher than that may be okay but they may not provide as much light as they should. They're not designed for direct contact with insulation so you don't want to recess them into the ceiling.

 

[JordonMusser]

Thanks, that is what I thought. I will either frame around them with an air gap (no insulation) or surface mount with some trim around them.

They will be on the vaulted ceiling, 8 total fixtures, 4 running down between each car(breaking up in 1/3rds) just under 13ft from ground level.
There will be two additional fixtures directly over proposed work areas as well (10 total 4 bulb fixtures in the 30.7x25.5 garage)