Need a little expert advice

so I have a grow area 30"x48"x6 1/2" Tall. Soil grow, would like to do SOG style grow. How many watts should my HPS be to pull this off, also how much ventilation am I going to need??

so lets convert 30 inches is what 2 1/2 feet by 4 feet by 6 feet tall a 400 watt hid light covers a 3x3 area so if arranged correctly a 400 watt light will do but a 600 watter is so much nicer and better..you have 72 sq feet of room so you need a fan that is able to clear that quickly.look for a fan that is rated for 72 sq feet.Id say a simple inline 6 inch fan from homedepot will be fine..sincerely FilthyFletch

Am I going to need a intake and outake fan? or is a intake fan not needed?

Use both but your intake can be smaller like a 4 inch inline fan they cost $24 at home depot and like $38 for the 6 inch fan by the heating and ducting stuff

The inline fans from Home depot are not the greatest so maybe one coming in and going out, if you get a fan with a lil more ass on it, a well placed passive intake should suffice.

A 6 inch inline home depot fan is rated at 350 cfm so that 5 times the amount of his room so it can clear it very well

Yeah I know the exact fan you speak of, in fact I have one sitting in a pile of parts I dont use anymore.... because they perform poorly. They are in fact designed to aid your existing air handler, and with a non restrictive intake they may indeed work. If however there is even the slightest restriction the overinflated manufactures rating will diminish significantly. btw when we talk about volume most people say cubic feet, afterall square feet is a measurement for area.

The cfm on those fans isnt really that bad I have used them for years and even have done back pressure tests on them to see what type of reducers I could use without sacraficeing actual output.The fall within 50 cfms of stated output.In an 8x8x10 foot room I use 2 6 in outlets and 1 4inch inlet and can exchange the rooms complete air in under 5 minutes.I was able to gauge this by using my co2 ppm monitor/controller.It tells me co2 ppm before adding then runs it to 1500 ppm and when I do an air exchange the new ppm reading will go back to prior co2 injection ppm levels in about 8-9 minutes showing a complete room air exchange.Now these dont work well with full on carbon scrubber filters as the power is lost from the masive restriction which is why when you buy a fan for a filter you should almost double the need room cfm to get the correct amount of mass flow.

Not sure what ya got there. Sounds like two of the fans maybe being used for exhaust, both adding up to 700cfm for a 640 cubic foot room clearing in under five minutes.... not bad. Props. Wish I could have made them work, they're not very noisy at all compared to my squirrelcage I wound up with. As you pointed out though they are not very well equipped for pulling through a carbon filter or poorly maintained intake filter/screen. My paranoid nature would not let me exhaust without pulling through a carbon filter first, I am naive I guess, figured that was standard.

Out of curiousity is your four inch inlet passive, or is there a fan there as well? If it's passive your room may clear even faster if you popped another four inch inlet into the room. Just a thought.