thanks for the link, but he states this in there about ventilation and i disagree with his figures on size fan. isnt that fan too small

The space needs to have enough airflow to both remove heat from the lighting, moisture in the air put there by the plants and provide adequate CO2 for the plants. This means a ventilation system that will exchange the entire volume of the room air in about 3-5 mins max. Work out your room volume by multiplying room length x width x height and then go shopping for exhaust fans based on that figure. A 1000 cubic foot room needs a 200 CFM (cubic foot/min) exhaust fan. If you can't ventilate the space, you can't grow in it.

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how to use an industrial low bay light fixture
http://www.rollitup.org/do-yourself/...l-low-bay.html