Ventalation

I Recently purchased a 100 watt high pressure sodium light to grow with.... and I am not financially ready to get an exhaust system to get the air out of my grow room... The room (an attic) is rather large (about 20 feet by 20 feet and about 6 feet tall) and there is a kind of small opening where air can escape and come in. Im Growing 2 plants at the moment and i plan on letting them grow big. The air temperatures reach about 75-80 in the day and 60-65 at night Do I really need any more ventalation for this room?

you should be fine, a fan would help a little and it would make your plants stronger

get a computer fan and DIY with a 12v ac/dc adaptor,if you havent checked that out already, and thatll definitely get your plants swaying real nice

A room that size get a box fan at a thrift store.

the purpose of the fan is to thicken the stem growth? Will this effect the yield of the plant or will this just help the plant support the buds?