if your floor area is 8 x 16, to start you will need more lights... i would say double stacked along the 8 foot way so 4 is def covered and 4 the other way... so in total you would need... 8 (1000 watt lights to optomise everything)... So it would look like this...
______________________________
! !
! X X X X !
! !
! !
! X X X X !
! !
!_____________________________!
X's are the lights, using the optimal 4x4 foot light area's.
Side note :Invest in a good air conditioner for this, in almost any climate south of mason dixon, this area will be a fucking dessert without one. I would recommend a good 8,000 or 10,000 btu