Grow room design advice

[whitewidow2]

HI i posted this in the newbie section but ive not got a decent answer yet so thought id post it up here..... can anyone help???

Ok... so ive started posting on here and im already growing as some of my previous pics have shown. Probelm is my setup isnt exactly ideal at the moment - i have a cupboard 50cm x 80cm x 165cm with swing open doors at the front and a stand alone fan inside to circulate fresh air.

What i WANT to do is have an inlet and outlet using pc fans to circulate the air and the reason this hasnt been done yet is it involves some modification to the unit.

I understand that fans have a CFM rating (cubic feet per min) and with the help of

https://www.rollitup.org/view.php?pg=...article&id=227

https://www.rollitup.org/view.php?pg=...article&id=229

i have worked out that my cupboard has a cubic volume of 21.62 cubic feet (bit of maths involved 1cm = 0.032ft) so basically i have worked out that i need a fan with a rating of approx 65 (multiplied the cubic volume by 3 assuming it needs 3 changes per minute) ie a 65CFM fan and from my research i see that the 120mm 12v fans have the highest CFM ratings so ill probably go for one of them.

Now im gonna put this fan at the bottom of the grow cupboard to let the air out and eventually carbon filter it...

Whats confusing me is it talks about passive intakes (ie no fan reqd.) i would have thought you needed a fan to push air in to the grow room as well?

And also - once this is done, will i still need my oscillating stand alone fan in the grow room for circulation or will the new setup be enough?

Please anyone who has any experience can you lend me a hand - thank you.

The cupboard http://www.ikea.com/gb/en/catalog/products/14903207

 

[WoldofWeedcraft]

Use one of the PC fans near the top of the cupboard for exhaust. Also, cut a hole near the bottom, maybe on the opposite side of the cupboard for passive intake. You can do active intake, but if you do, make sure the fan for your intake is lower CFM's than the exhaust fan. The idea is to create a neutral pressure in the box, or maybe a slightly negative pressure (meaning that more air is exhausting than intaking). The oscillating fan should stay inside the box to blow air on the plants (mimicking wind) to keep them growing stronger so they don't fall down when the buds stack up.

 

[luv2grow]

cut the intake hole in the bottom left or right corner at the front of the cab and exhaust on the opposite side at the back of the cab at the top. No intake fan. just like weedcraft said you want neg pressure so the heat is exhausted and not having a fan on the intake will save ya money on the power bill in the end plus the cab. being raised like that is perfect for a passive intake. Good Luck.

 

[justhav2p]

Keep your oscillating fan,.... are you going to use a vented hood? My setup is 2 birds 1 stone. I Vent the heat from my light and pull stagnant air out of the room and use my a/c to supply fresh air in.

 

[whitewidow2]

Use one of the PC fans near the top of the cupboard for exhaust. Also, cut a hole near the bottom, maybe on the opposite side of the cupboard for passive intake. You can do active intake, but if you do, make sure the fan for your intake is lower CFM's than the exhaust fan. The idea is to create a neutral pressure in the box, or maybe a slightly negative pressure (meaning that more air is exhausting than intaking). The oscillating fan should stay inside the box to blow air on the plants (mimicking wind) to keep them growing stronger so they don't fall down when the buds stack up.

Thanks man. Ive just had so many different theories that it was getting me confused like i say its just a small grow area for 5 plants max... so what do you think... should the inlet be passive or have a fan? And the thing about the CFM rating - have i got that right - should it be approximately three changes per minute like in the article above?

 

[WoldofWeedcraft]

Passive intake will be fine. For your CFM's, convert your dimensions to feet (above you posted in cm) and calculate the cubic feet of your space. Lenght x Width x Height (all converted to feet). And based on how many cubic feet you have, make sure your fan is more than this amount in CFM. I have a 4'x4'x6.5' flowering space, and that equals 104 cubic feet. So I know my fan has to be over 104 CFM's, so I chose a 250 CFM fan (was just the best deal).

 

[WoldofWeedcraft]

Oops I didn't see you had already converted to cubic feet. Alright, well 3 changes of air per minute should be more than enough if you can find a 65+ CFM pc fan. I think you would probably only need 3 changes per minute if you were using HID lighting though.

 

[whitewidow2]

Thanks a lot man you have been very helpfull so basically im thinking a passive intake at the bottom and a fan at the top at the opposite side (cpu fan approx 40 to 65 cfu) to extract air - a home made carbon filter attached to the outside of it, probably a tub of ona inside the growroom too and keep the oscillating fan in there too.

How big do you think i should make the passive hole at the bottom.. it should be slightly larger than the one exiting at the top right?

Also is the reason for having the outlet at the top due to the warm air rising?

It doesnt really get too hot in there as its just a single 150wCFL suspended from some hangers but im still a newbie and i need to get a temp sensor too it seems.

 

[WoldofWeedcraft]

How big do you think i should make the passive hole at the bottom.. it should be slightly larger than the one exiting at the top right?

Also is the reason for having the outlet at the top due to the warm air rising?

I would make the intake at least the same size. I use ducting and bend it so that my intake doesn't let light in, and it's the same size as my exhaust.

Yes, the exhaust is at the top b/c of warm air rising, and the intake is at the bottom for the opposite reason.

 

[whitewidow2]

Guy at the local hydro shop says a pc fan wont be strong enough to pull air through a proper carbon filter???

Whats your views on this...

 

[WoldofWeedcraft]

Guy at the local hydro shop says a pc fan wont be strong enough to pull air through a proper carbon filter???

Whats your views on this...

Not for a professional one like they sell at the hydro shop. Those are big and round and have small particle filters on one end and large particle filters on the other. They are the best filters and work well for a big room, but if you're using a small space and you want to do a DIY one, there are some great recipes that would work with a small fan like what you plan to use. Check out Wolfman Zen's cheap DIY filter in the DIY forum. If all you got is a tiny space, that's the way I'd go.

 

[DaGambler]

you can get a inline duct fan at Lowe's or Home Depot that'll work well enough. though i'd say upgrade to a closet grow
.