large growing room design

Hi
Have 20 x 30 foot growing area part of a 20 by 45 foot garage remote ideal and in construction. thought of only using 20 by 30 and exausting drying etc in other bit. Thats as far as i have got as still building it.

whats the best lay out, number of plants etc and can someone please explain the Co2 question. I get confused thinking about putting Co2 in and fans taking it out every few minutes. just dosent make sense somehow.

Know it aint going to be easy and experiance required but desperate. Any advice greatly appreciated,

Regards
Le tiss

Hi Should have said intending NFT and got a great deal on floresant and 400M/hilide and Hp sodium lights/ 8 in total so far but 1500 available at great price.

Cant get deal on 600 or 1000 so restricted. Height 10 foot insulated room clear floorspace. Water and electric no problem. Total novice havent a clue and refused OAP. Fuck um. Three sqaure a day in prison so nothing to loose.
regards
le tiss