Grow room venting question!!

BeaverHuntr

BeaverHuntr

Well-Known Member
New guy here almost done with my grow room it is looking kick ass.. I have a noob question. I brought in the AC duct from the spare bedroom into the walk in closet, and I will be exhausting the air with a 6'' can fan and filter on the ceiling into the attic .. Since I have the AC bringing in fresh cool air do I still need a intake hole??? Also how often should I run my can fan ?? every 30 Min on then 30 min off? Thanks in advance.
 
You can get a attic fan termostat at you local hardware store that you can wire to turn your fan on only when its hot. I got mine for 25 bucks.
 
Dirtfree said:
You can get a attic fan termostat at you local hardware store that you can wire to turn your fan on only when its hot. I got mine for 25 bucks.
Click to expand...

Cool I will look into that. I will leave my AC on 80 degrees while I am at work , and then down to 75 when I am home. This attic fan thermostat will control the can fan ?
 
Ya you have to get a box and a outlet and an old extension cord(or wire and a plug). You can set it to come on at any temp you want.
 

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So my room is set up .. Test run made me sad. Could not get temps under 93 degrees even with AC , have a 6'' can fan and 1000W MH running ..lowest temps I could get are 93 degrees the fan is exhausting in the attic... The room is 5' 6' 8 ' high . Looks like I might have to go T5??? any advice?
 
fatfarmer said:
Down size MH lights before you change them.
Click to expand...

I can buy smaller bulbs right? Checked the room this morning with everything off and the AC going and it was a cool 76 degrees. Today I will check the vent in the attic make sure the hot air isnt coming back down to the ducting.
 
How is your CanFan venting ?

Does it have bends or is it straight ?
30 degree bends cut rate by 10% EACH BEND.
90 degree bend cuts the CFM's by 30% - 50%.
Also, does your A/C vent hot air into your grow room or do you vent that into the attic also ?

You may either need to upgrade to a larger fan OR vent the light and room seperately.
I have a 6 inch CanFan too. The regualr that is 276 CFM, not the High Output that is 440 CFM.
Your room is 240 Cubic Feet.........5 x 6 x 8 = 240
With a filter attached, your fan is also reduced in CFM a little and that makes it barely adequate to vent your space.
May need to go with the H/O 6 inch or an 8 inch regular or H/O.
Remember, you need enough negative pressure to get that heat out of there.

Hope this helps.
 
with the appropriate size intake & exhaust fans to create negative pressure, and using a small personal style fan on the floor of my grow room, i have been able to cut my room temps by 11 degrees.

even during the day (daytime heat of the summer in my detached garage), my three grow closets stay at 84 to 87 degrees.

i think : fresh air intake & proper venting are the most important, and most overlooked, aspects of a good grow space.

flo grow gave you some good advice. it' all about cfm & moving air.

vent the room & vent those lights.

air cooled hood with glass cover helped me.

how about running your set up at night to take advantage of cooler temps?
 
gudkarma said:
with the appropriate size intake & exhaust fans to create negative pressure, and using a small personal style fan on the floor of my grow room, i have been able to cut my room temps by 11 degrees.

even during the day (daytime heat of the summer in my detached garage), my three grow closets stay at 84 to 87 degrees.

i think : fresh air intake & proper venting are the most important, and most overlooked, aspects of a good grow space.

flo grow gave you some good advice. it' all about cfm & moving air.

vent the room & vent those lights.

air cooled hood with glass cover helped me.

how about running your set up at night to take advantage of cooler temps?
Click to expand...
..

I test ran it last night and the temps would go no lower than 91 degrees. Here are some pics..

SDC11555.jpgSDC11553.jpgSDC11552.jpgSDC11554.jpgSDC11551.jpgSDC11556.jpg
 
Flo Grow said:
How is your CanFan venting ?

Does it have bends or is it straight ?
30 degree bends cut rate by 10% EACH BEND.
90 degree bend cuts the CFM's by 30% - 50%.
Also, does your A/C vent hot air into your grow room or do you vent that into the attic also ?

You may either need to upgrade to a larger fan OR vent the light and room seperately.
I have a 6 inch CanFan too. The regualr that is 276 CFM, not the High Output that is 440 CFM.
Your room is 240 Cubic Feet.........5 x 6 x 8 = 240
With a filter attached, your fan is also reduced in CFM a little and that makes it barely adequate to vent your space.
May need to go with the H/O 6 inch or an 8 inch regular or H/O.
Remember, you need enough negative pressure to get that heat out of there.

Hope this helps.
Click to expand...

Can Fan venting up into ceiling ( see pics )
Defintely bends in the ducting.
I have the can fan 33 the box says 400 cfm .
The AC is blowing in cool 75 degree air the same as my house.

I germinated my beans last night and I hope I dont get any sprouts before I get this heat issue resolved.
 
gudkarma said:
with the appropriate size intake & exhaust fans to create negative pressure, and using a small personal style fan on the floor of my grow room, i have been able to cut my room temps by 11 degrees.

even during the day (daytime heat of the summer in my detached garage), my three grow closets stay at 84 to 87 degrees.

i think : fresh air intake & proper venting are the most important, and most overlooked, aspects of a good grow space.

flo grow gave you some good advice. it' all about cfm & moving air.

vent the room & vent those lights.

air cooled hood with glass cover helped me.

how about running your set up at night to take advantage of cooler temps?
Click to expand...

The hood is air cooled with glass.. Still scratching my head ..
 
Alright BH, we're gonna work this out. Plus the heat will help your seeds sprout for now.

Here's your problem, judging from the pics, and starting from the ceiling TO your filter :

Drops from the ceiling into 180 DEGREE BEND
Into your fan with a 90 DEGREE BEND
Out the fan with a 90 DEGREE BEND
Into the hood with a 180 DEGREE BEND
Out the hood with a 90 DEGREE BEND
Into the filter with another 90 DEGREE BEND

For arguments sake, let's assume that EACH bend only takes away 10% of your CFM's, even though it's WAY MORE than that.
That means you are losing 60% (6 bends x 10%) of your CFM's = 240 CFM's being robbed.
That leaves 160 CFM's to vent a space that NEEDS AT LEAST 240 CFM's.
See where I'm going with this ?

If you insist on running ducting, you need to tighten up all that wasted excess. Too much ducting for all that air to be pulled through.

You will get max extraction if you can attach the fan directly to the ceiling with the filter hanging straight down. Or connect the filter to the fan and run ducting straight from the fan, with just ONE 90 degree bend into the attic. Get a second fan (smaller) to vent the hood seperately into the attic.

I had issues venting my Homebox Large tent. I run a 400w Horti in a Sun System Yield Master II Supreme 6 inch hood with glass lens.
Had bends too (two 90 degree bends) and gave me probs.
Fucking around, I said let me run the fan straight into my attic and take the lens cover off my hood.
So my fan sits on top of my tent, outside, with 3 feet of ducting STRAIGHT into the attic.
Even in this Summer heat of 105F, my tent stays 6 - 7 degrees above ambient or around 84F.
No air cooling the hood and light. A small fan blowing on my light and that's it. Not to mention enough passive intake to create that negative pressure.

If you don't have enough power to pull all that heat from the hood, it gets trapped, builds up, and dissipates into your grow area. Although I am not air cooling my hood with the lens and all, my fan is working at it's full capacity with no bends from ducting to hamper it because it's a straight draw from my tent into the attic. NO FILTER EITHER ! Having 3 - 4 plants that are 2 - 3 feet tall doesn't make that much of an stinch for me to worry about the smell in the attic. The smell will dissipate too, once in the attic.
I don't even smell my plants when I'm in my walk-in closet, until I unzip my tent.

I hope this long winded response helps !!
 
Flo Grow said:
Alright BH, we're gonna work this out. Plus the heat will help your seeds sprout for now.

Here's your problem, judging from the pics, and starting from the ceiling TO your filter :

Drops from the ceiling into 180 DEGREE BEND
Into your fan with a 90 DEGREE BEND
Out the fan with a 90 DEGREE BEND
Into the hood with a 180 DEGREE BEND
Out the hood with a 90 DEGREE BEND
Into the filter with another 90 DEGREE BEND

For arguments sake, let's assume that EACH bend only takes away 10% of your CFM's, even though it's WAY MORE than that.
That means you are losing 60% (6 bends x 10%) of your CFM's = 240 CFM's being robbed.
That leaves 160 CFM's to vent a space that NEEDS AT LEAST 240 CFM's.
See where I'm going with this ?

If you insist on running ducting, you need to tighten up all that wasted excess. Too much ducting for all that air to be pulled through.

You will get max extraction if you can attach the fan directly to the ceiling with the filter hanging straight down. Or connect the filter to the fan and run ducting straight from the fan, with just ONE 90 degree bend into the attic. Get a second fan (smaller) to vent the hood seperately into the attic.

I had issues venting my Homebox Large tent. I run a 400w Horti in a Sun Sysytem Yield Master II Supreme 6 inch hood with glass lens.
Had bends too (two 90 degree bends) and gave me probs.
Fucking around, I said let me run the fan straight into my attic and take the lens cover off my hood.
So my fan sits on top of my tent, outside, with 3 feet of ducting STRAIGHT into the attic.
Even in this Summer heat of 105F, my tent stays 6 - 7 degrees above ambient or around 84F.
No air cooling the hood and light. A small fan blowing on my light and that's it. Not to mention enough passive intake to create that negative pressure, which is why I overcame the heat issue.

I couldn't believe it ! Cooler than it's EVER been during the Summer !
Click to expand...

Thanks dude ..Back to work so I will post in a couple of hours and let you know how it went post some more pics too .. Thanks Flo and everyone else ..Tomorrow I will just go to the grow store and get a second 6'' inline fan . They are closed Sunday.. Ba ba bummer. Anyways just going to run the fan to the hood. and check temps .. not using the filter since these are only test runs .
 
Flo Grow said:
THAT'S what's up !! lol

Did you remove some of those bends from the light to the fan and the fan to the ceiling ?

Pics please ! lmao
Click to expand...

Yes I got rid of all the bends.. Now using maybe a whopping 2-3 feet of duct. Its 86 but with the fan running full time.. Could i get a smaller MH bulb to bring down the heat too?? Pics this evening when I get home.
 
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