I know I saw a thread on this....or something that answered my question. I cant find it now for some reason though...Anyway, my question is: If using a 400w HPS light...whats the minimum size of the growspace needed? Im sure too small of a space would raise the grow are temp alot.

So, what is the smallest space you can use that type light in without harming the plant directly or causing the room temp to rise too much?

If you can keep the grow area around 70-80 degrees any size you wish. YOu can use fans or air cooled hoods to help if you are in a confined space, but no fans, no cooled hood probably something like 4 x 4 x 7. With proper ventilation.

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i use my 400w w/ a digi ballist in my closet in a 2x3 space. on week 4 of flower of my first crop and the results are quite nice.

"If you can keep the grow area around 70-80 degrees any size you wish"

So the minimum distance between plant and light is determined by your ventilation, not the light. Put a kick ass extractor at the base of the light to prevent a 'hot spot' and you are sweet?