help with lighting

We are first time growers building a 12' x12' room. Have decided to use HPS and MH but are unsure of how many and what wattage we should use. We are only going to grow 12 plants. Your suggestions are welcome - Thanks

I would say 400+ watts MH/HPS for 12 plants.

soo... 12 square feet/plant?? VV

Saving plenty of room for future growth! We are not exactly sure what all we will need so we planned for plenty.

We have decided on two 600 watt HPS/MH systems from HTG. How big of a problem will heat be in a 12x12 room? We have 8'ft ceilings. We are planning to surround the plants with reflective mylar. Will this increase heat. Any help is appreciated.

Mylar does reflect heat.
Are you planning on to get any form of ventilation?
Ventilation is not only required but most effective on temp control.

and smell control.

We know we need ventilation but we aren't sure what the best way to go about it. Will a few fans work? Should we put in exhaust fans. Initially we will be growing in winter and we are thinking the lights will keep it from getting too cold. What other things should we consider?