Help on a 4x4x6 grow room

Hi all, well the time has come for me to start thinking of design ideas for a grow room. I have read alot of posts and seen their designs. I have learned a bunch and am very thankful for this type of community. My question is this... with that size room set up with the standard venting set up, Mylar reflecting put up ...will a 400 watt HPS be enough light? Thanks in advance for all your thoughful answers

i ran a 600 hps in a room a bit smaller than that(3'4"x 4'x6'), so a 400 would work with a little venting. I ran two 6" inline fans (home depot) one inake, one exhaust. I did mount my ballast outside the room.

I have been having wonderful success with my new LEDs. My space is larger, 10 X10 X 12, but as I am in Colorado and can only legally grow six plants, LEDs have been working beautifully with some important considerations. #1 LEDs heat is so nonexistent that I have had to place a space heater in my room to maintain proper temp. #2 LEDs require no ballast, and use very little electricity. #3 My LEDs have life expectancy of 50,000 hours and came with a two year warranty. #4 intermodal growth is extremely small ( I'll down load some pics for you to see ) . #4 My LED panels measure only 18"X 8" but, because you hang them higher above your plants, I am able to easily fit six five gallon buckets beneath them. I use 2-120W panels with an expected energy usage of approximately $185 dollars per year, and my lights cost me only $150 each, and things which destroy other light sources ( accidentally spraying with water, or small drops, mine pulled hook out of ceiling and fell three feet to concrete floor and took no damage, my bad I missed ceiling beam when hanging lights ) are not serious considerations when using LEDs. I know there is a lot of resistance to this new technology, but if you try it I am sure you won't be sorry. The plants in my pics are just shy of eight weeks from the time I planted germinated seeds. I took some pics with ordinary light as pics taken under LEDs appear pink as seen below.

View attachment 916941View attachment 916942View attachment 916944 I do also have a small full spectrum floro, and an infrared spotlight to provide under lighting, and orange spectrum. If you have any questions, please don't hesitate to ask.

Ive got a 600 watt in a 3ftx3ftx6ft with ok venting and it is good. I think you could be ok with a 400watt in a tent or room no larger than 5ftx5ftx5ft.........youll lose lumens

Thanks for all the replies, LED does interest me but I have to go cheap this grow. I did find the parts to make a ballast and I have a donation on the bulb so I'm gonna use the DIY guide to make my light. Other than that i guess I need to start a journal to record my progress ....or failures (lessons)....it's been a bit since I last grew.