Just got some Darkroom Louvers and there's so little airflow they are WORTHLESS!!

[BennyHogan]

I bought three 4 in Darkroom Louvers from the Builders Depot and they let so little air pass thru them that they are absolutely pointless in my opinion! You would need at least 4 or 5 of the four inch louvers to mimic the airflow of an unrestricted 4 inch hole.
I was recommended these by someone on here and don't want someone else to make the same mistake.
I'm now back at square one in terms of light-proofing my cab.....I've tried PVC piping and can't get anything to hold the weight of the piping. Maybe I'll have to build a cardboard box or something??? Any ideas???


Cheers

 

[DIGITALHIPPY]

they allow such low air-flow because they block light, its light or airflow.

 

[FreezerBoy]

Cardboard's good. Opaque, cheap, plentiful, easy to work with ...

 

[BennyHogan]

they allow such low air-flow because they block light, its light or airflow.

I can't believe how many people use these things with how little air they allow thru them.....I need to find a simple design I can easily copy to light-proof a couple of circular holes.

Peace

 

[smoke1sun]

Darkroom louvers are a must for the steath grower. When i first got mine, i said the same thing. But when i shut the door in my room i notice a big difference, i had to get over the fact that, its not the same as a open hole. The air movement is not gonna be as strong. When i trusted other growers it worke out fine. or i should say better cause now i had air movement without the light leaks. If stealth is not a priority, then louvers are a waste. But in my case my cab was in a bedroom, that we use, and we are renters, so light leaks were a no no. Weight your options check your temps with and without. and always keep your reciepts. LOL

 

[FreezerBoy]

I can see how they'd be helpful in stealth but, they're not required. Obviously, the location of the cab has much to do with it. I've got three 4" holes in my cab. The one exhaust at the top has a duct hose attached that simply hangs to the ground. The 2 bottom intakes are covered only by aquarium filter material to keep out bugs and dust. Boxes around the cab block virtually all escaping light. Yes, if you stand in the closed garage in the dark for several minutes you can begin to sense a glow but, nobody ever gets to do that.

 

[Azeotrope]

I have been using the 8" square darkroom louvers for quite some time now. They work great. I know a hobbiest (like me) that uses the 4". They are great.

The issue is usually the grower and their lack of understanding static pressure. It is very easy to underestimate the required passive intake area (opening(s)) required, or to over estimate the capacity of there fan versus static pressure/retrictions.

For example, many folks here use axial or "pc" fans. They are cheap, and should be as they are horrible at moving air against static pressure. Some folks use a squirell cage or "blower wheel" type of fan, again very poor at working against static pressure. A quality centrifugal in-line fan and an overkill amount of passive intake is really the best way to go.

So, that said someone will hit me with some kind of "we can't all have the 440cfm 6" Vortex or the 6" Elicient (both the only fans I will touch). Or an alternate size of the two. In that case folks need to buy high quality 120/208/220/230VAC axial fans and apply them correctly. I know I am sounding like a stuck up engineer, but that is what I am (in several specialties) so bare with me. The link below is the best refrence point that I can link you to to explain how to use axail fans at there top end. From there on you must have, well, let's just say "WAY MORE" passive intake than you would ever think. For stealth, there is no beating the darkroom louvers.

Here is the link for you axial fan guys. Oh, and I use them some times for spot cooling and used them exclusively for years. In series.....Until I graduated.


http://www.nmbtech.com/html/fans/engineering/engineering_101.html

http://findarticles.com/p/articles/mi_m0BPR/is_11_21/ai_n13481089


The nmbtech link is great!!

 

[petemoss]

According to this table from S&P, a squirrel cage fan like the Dayton is fairly good at moving air against static pressure. Not a good as an in-line centrifugal fan, but much better than an axial. I've used a Dayton 265 and found it pretty effective in pulling air. After about six months, the Dayton became pretty noisey.


As far as the darkroom louvers, I use two 8"X8" in my wardrobe cabinet. Although they seem to block out a lot of airflow, enough air gets through to keep the air inside moving smoothly without major restrictions.

I have a smaller cabinet that could use the 4" midget louvers, but I'm not sure whether they will restrict the airflow too much. The description for the 4" louvers states:

= Size - 4-inch
= Inside Diameter - 3.96-inch
= Outside Diameter - 4.5-inch
= Collar - 25/32-inch
= Approximate Free Area - 3.45 square inches

3.45 sq in "free area" sounds like they would work OK. About 3/4 of a 4" hole would be blocked by the louver, so you would need at least three louvers to pass as much air as a 4" diameter hole.

 

[Azeotrope]

Squirrel cage fans suffer bearing wear from high load, the cups collect dirt easily, they are generally not efficient as far as kwh consumed versus work done. However you are quite correct that they will overcome notable static, just at a price. The higher quality in-lines Ie. Elicient, fantech, panasonic, vortex will last much longer, run quieter and more efficiently when installed correctly.

 

[FirstTracks]

i used a combination of 4" midget louvers and an 8x8" louver for my 150w dresser cab.

8x8 for main intake and 4inchers on the in and out of the cooltube ducting. it worked quite well for blocking out all the light, and though all cut down airflow, they were very much worth it as I needed the dresser not to glow because ummmm........dressers don't glow.

like its been said, you need to understand the static pressure increases they cause and be willing to accept the tradeoff of airlow for stealth. you can always add more intakes.......thats what i did.

 

[petemoss]

Good info, FirstTracks. Thanks. I never even considered the light leaks from the holes.

Benny, I forgot to mention this: the 8X8" louvers have four layers of slats. They say you can remove one or two layers to increase the airflow.

 

[BennyHogan]

I'm using a 90 CFM HydroFarm Active Air Blower and when I put a louver over the hole it sounds like a tea kettle!!
After hearing how little air was escaping, I fear that using them over my intakes (while stealth) would not be the best for the p's.....I want to keep things stealth but I'm also a leg med grwer so I'm just keepin it stealthly concealed from visiting friends/fam.
I'm gonna mail these louvers back I think......or I could cut 3 four inch intake holes and use them all there....then I'd only have to worry about my current 4 in exhaust. But I still don't think the 3 four inchers would allow sufficient airflow.

 

[Azeotrope]

A 90cfm fan might cool a 70 - 150w grow cab if used correctly, but I would still have 6-8" of passive intake that is unrestricted or 5-6 of those louvers.

 

[phillykid]

What about an area 7ft X 3ft X approx 8ft height. The original plan was put a 12X24 darkroom louver in the door and use S&P TD 200X 478/419 CFM 8in inline on a speed controller for exhaust. The fan will be connected to an air cooled hood. The front of the door would have the louver, the back would have a flange to connect ducting to the light, after the light (1000 HPS) there'd be a Y adaptor and then the fan.

I wanted to get air flow from outside the closet directly to the light and also pull air into the rest of the closet with 1 fan. The flange on the back wouldn't cover the entire louver and I figured as long as the light is staying cool, I wouldn't need quite as much venting for the rest, just enough to exchange stale air.

It's only for fall/winter months in the northeast. Is it enough or will it be loud and craptastic?

 

[Whatever]

I love my dark room louvers but important to oversize if using it as a passive intake. I'm pretty sure one of them I have, a 12' x 12', is rated for 420 cfm but that's when used actively. I installed a 12' x 24' in a mother room and it's used passively and works just fine.

 

[messn'n'gommin']

I'm using a 90 CFM HydroFarm Active Air Blower and when I put a louver over the hole it sounds like a tea kettle!!
After hearing how little air was escaping, I fear that using them over my intakes (while stealth) would not be the best for the p's.....I want to keep things stealth but I'm also a leg med grwer so I'm just keepin it stealthly concealed from visiting friends/fam.
I'm gonna mail these louvers back I think......or I could cut 3 four inch intake holes and use them all there....then I'd only have to worry about my current 4 in exhaust. But I still don't think the 3 four inchers would allow sufficient airflow.

If using three of the 4" louvers gives you about 12.75 square inches of intake and an unrestricted 4" hole is about 12.25 square inches that is, more or less, a 1 to 1 ratio of intake to exhaust. I would think an 8" by 8" louver being restricted by as proportional an amount as a 4", would equal about 21" of intake. Almost a 2 to 1 ratio of intake to exhaust, the "accepted" norm for ventilation.

Namaste, mess

 

[Azeotrope]

messn -

2/1 or greater is a great place to start. As long as it can be kept light tight it is hard to have too much passive intake.

 

[phillykid]

Azeotrope, you seem to know your stuff where this is concerned, mind commenting on my post? The S&P inline is mixed flow, pete moss's little picture thing is from S&P. Trying to cut the noise but hopefully still have enough oomph to get enough air through a 12X24 dark room louver. If this isn't possible then maybe I'll have to go and make a maze of PVC in the inside and use a regular non light proof grill on the front to hide the holes.

 

[simpleword]

I made this diagram for a passive intake baffle a couple months ago. Just make it big and it works a charm!

 

[messn'n'gommin']

messn -

2/1 or greater is a great place to start. As long as it can be kept light tight it is hard to have too much passive intake.

I agree wholeheartedly Az, and that was why i put the word accepted in parenthetical quotation marks. As a matter of fact I am currently using one 8x8 louver opposite a Stanley blower with a 4" exhaust and plan on adding another 8x8 soon. Since I do not particularly like restricting the Stanley to 4" I am also seriously considering stepping up to a 6" exhaust. But, I will see how the addition of another louver will work before I increase the exhaust port. I was "assuming" that benny is growing in a Mills Pride style or NGB style box. Which would limit, somewhat, the amount of area available for ventilation, hence, the reason for his purchase of three 4" louvers and having one 4" exhaust. It occurred to me that the one to one ratio was the biggest part of his frustration with the louvers and trading in the three 4"er's for an 8x8 would offer him an adequate flow rate and still have the kind of light-proofing he wants/needs. I apologize for any misunderstanding I may have caused and hope everything works out.

Namste, mess