Hello, I just finished putting insulation and walls in my unfinished, unattached garage. Now to help keep the heat in and make it look better, I want to put a ceiling and some R19 up. My question is, what building material would be best for the ceiling and also, can I even do this because its made of 2x6's running a 15' span at 48" on center. I know I would have to add wood to keep anything I put up from sagging, but will the construction be strong enough to hold all of that up and some storage also? Thanks in advance!