Ventilation for 10x10 grow tent a little help/experience needed

i'm looking for vent options for a 10'x10'x6.5' grow tent. doing the math for 3 exchanges/min i'd need a 1950cfm fan. none of the inline fans are close to that much unless i'm getting a heavy duty one and spending mad cash, but then even the huge carbon filters only have a max airflow of 1400cfm. i'm stumped what's the best way to vent my tent with carbon filter?? what have you guys done?? these 10x10 tents seem pretty common, what am I missing here??

u did the basic math ...............here u go this accounts for all the varibles with indoor growing ...............

and your numbers are a off .....u need minal of 217 cfms WxLxH then u devide that by 3 for your minal

Dan's Method
Calculating By Room Volume You will find many calculations on the web for sizing a fan for ventilating indoor gardens; however, what many of these calculations fail to take into consideration is the friction loss on carbon filters and increased temperatures from HID lights. So here's my calculation method which you can use as a guide for sizing an exhaust fan for a growing area (keep in mind that this calculation will give you the lowest required CFM (Cubic feet of air per minute) required to ventilate the indoor garden.)

Step 1: Room Volume
First the volume of the room needs to be calculated. To calculate multiply length x width x height of growing area e.g. A room that is 8' x 8' x 8' will have a volume of 512 cubic feet.

Step 2: CFM Required
Your extraction fan should be able to adequately exchange the air in an indoor garden once every three minutes. Therefore, 512 cubic feet / 3 minutes = 171 CFM. This will be the absolute minimum CFM for exchanging the air in an indoor garden.

Step 3: Additional factors
Unfortunately, the minimum CFM needed to ventilate a indoor garden is never quite that simple. Once the grower has calculated the minimum CFM required for their indoor garden the following additional factors need to be considered:
Number of HID lights — add 5% per air cooled light or 10-15% per non-air cooled light.
CO2: add 5% for rooms with CO2 enrichment
Filters: if a carbon filter is to be used with the exhaust system then add 20%
Ambient temperature: for hot climates (such as Southern California) add 25%, for hot and humid climates (such as Florida) add up to 40%.


An Example
In our 8' x 8' room we have 2 x 1000w air cooled lights, and we plan to use a carbon filter. We also plan to use CO2 in this room. The ambient temperature is 90 °F (32°C), however, we will be using air from another room that is air-conditioned. Here's the minimum required CFM to ventilate room:
1) Calculate the CFM required for room (see above.)
2) Add 10% (for 2 air cooled lights.)
3) Add 5% of original CFM calculation (For CO2.)
4) Add 20% of original CFM calculation for Carbon Filter.
5) Air is coming from air-conditioned room so no need to add any other percentages.
6) CFM = (171 CFM) + (171CFM x 10%) + (171 CFM x 5%) + (171CFM x 20%) + ( 0 )= 231 CFM.
This is the absolute minimum CFM required to ventilate your room.
The next step might seem to match the closest fan to this CFM. However, for this example I'd choose a six inch fan with a CFM of around 400 or more, and a 6 inch carbon filter to match. The extra CFMs may seem a bit excessive (calculations on most indoor gardening websites would recommend a 4" fan and a 4" carbon filter) but it's always better to over-spec since we need to compensate for air resistance in ducting too.
Also, as we are using a carbon filter we will need to match the fan with the filter so that the fan that will neatly fit onto the filter.
If all the variables are kept the same and we changed the room size from 8' x 8' to a 12' x 12' then the minimum required CFM would be 519 CFM.


The All-Important Inflow!
An intake port can be anything from a gap under the door to an open window - even a hole in the wall. The best place for an intake port is diagonally opposite from your exhaust fan; that way, air has to pass across the entire room - very efficient. You can put a piece of screen over the opening to keep insects and animals out, a piece of A/C filter to keep dust out, or a louvered shutter or backdraft damper that opens when the fan turns on and closes when it turns off. You can also use a motorized damper. This gets installed in-line with your ducting and is plugged into whatever device controls your exhaust fan. When your fan turns on, it allows air to pass. When your fan shuts off, it seals completely, preventing CO2, air, etc. from passing. You can get creative with these devices and use one fan to control two rooms, etc.
One additional note about intake ports - you will see much better results from your exhaust system if you install a second fan to create an active (as opposed to passive) intake system. Normally, when your exhaust fan sucks air out of your room, air is passively going to get sucked back into the room. By installing a second fan on the intake side, you will reduce the amount of negative pressure created in the indoor garden, thereby cutting down greatly on the amount of work the exhaust fan has to do and allowing much more air to pass through. If you're not sure or you don't want to spend the money, start out with just an exhaust fan. If it's not performing as well as you thought it would, try adding an intake fan - you'll smile when you see the difference!

thanks for your in depth response! much appreciated. you're right about my math being off. I read you wanted 3 exchanges per 5 min which would be 1950 per 5 min not every min, forgot to divide it by 5 for the per min calculation lol. my bad so I guess I only need 390 cfm based only on cubic feet, and 3 changes for 5 min, not taking everything else you said into consideration. good to know you only really need 1 per 3 min. thanks, i was definitely missing something. makes sense now.

well just rem to get yourself some extra power for those unseen varibles that might pop up later during your runs ...............u rather have it and not need it then need it and not have it

welcommes and goodluck on your grows

thx i just found a good deal on some used for 3mo equipment locally 840 cfm fan and 4ft can filter it looks huge. think that's too much?

i am a sucker for overkill ............u can never cover your ass to much ........u know in the movies where u see the guy unload a whole clip into a dead body to make sure they are dead overkill

with something that strong double check with who ever u are buying it from that a varible speed controller will work on your model
(those controllers do not work on booster fans) but they do work with inline fans

then u can use it on low or med for those cool days and if the temps spike u can move to high/ full on

IME,it is best to ventilate 1x-2x the volume of growing area per minute so...

10x10x6.5=650 cubic feet of grow area.

It is also best to use a seperate fan just for air cooling the lights.

If using a fan just for ventilation an 8" to 10" fan shpuld do.

In a room that size though I'd just seal it,run a ductlrss mini split,c02,dehumidifier,humidifier,etc.

one per minute is complete overkill, and a little bullshit. Maybe shoot for once every 3 and you will actually end up with once per 4 min. Which should be complately and totally fine.

Whatever you say bud.

ok, well post a link from some site about growing saying that you need 2x the volume per minute.


Under your brillant plan my new room would need 13,122 Cfm of circulation. Honestly, I don't even know how you would achieve such a think. 7 . 12" max can fans ... LOL

justugh said:

double check with who ever u are buying it from that a varible speed controller will work on your model
(those controllers do not work on booster fans) but they do work with inline fans

then u can use it on low or med for those cool days and if the temps spike u can move to high/ full on

Click to expand...

spend the extra and get a controller that is made for inline fans. the first thing you see when u open the package for that controller is "For use with brush type motors only" inline fans are brushless and hence should have a Variac controller. http://www.ebay.com/itm/Variable-AC-Transformer-500VA-variac-0-130v-ship-from-Chicago-/121162080727?pt=LH_DefaultDomain_0&hash=item1c35d2a1d7 it cost alil more but it is designed for use with inline fans. Spend a little more and save your fan, speed controllers will just cause you more heat, possible fire hazard, and shorter life fan. not hating on Justugh as he has help a great many of ppl on here myself included but sometimes its not being wrong as much as ill informed maybe.....

legallyflying said:

ok, well post a link from some site about growing saying that you need 2x the volume per minute.


Under your brillant plan my new room would need 13,122 Cfm of circulation. Honestly, I don't even know how you would achieve such a think. 7 . 12" max can fans ... LOL

Click to expand...

Jet engine on suck lol

justugh said:

u did the basic math ...............here u go this accounts for all the varibles with indoor growing ...............

and your numbers are a off .....u need minal of 217 cfms WxLxH then u devide that by 3 for your minal

Dan's Method
Calculating By Room Volume You will find many calculations on the web for sizing a fan for ventilating indoor gardens; however, what many of these calculations fail to take into consideration is the friction loss on carbon filters and increased temperatures from HID lights. So here's my calculation method which you can use as a guide for sizing an exhaust fan for a growing area (keep in mind that this calculation will give you the lowest required CFM (Cubic feet of air per minute) required to ventilate the indoor garden.)

Step 1: Room Volume
First the volume of the room needs to be calculated. To calculate multiply length x width x height of growing area e.g. A room that is 8' x 8' x 8' will have a volume of 512 cubic feet.

Step 2: CFM Required
Your extraction fan should be able to adequately exchange the air in an indoor garden once every three minutes. Therefore, 512 cubic feet / 3 minutes = 171 CFM. This will be the absolute minimum CFM for exchanging the air in an indoor garden.

Step 3: Additional factors
Unfortunately, the minimum CFM needed to ventilate a indoor garden is never quite that simple. Once the grower has calculated the minimum CFM required for their indoor garden the following additional factors need to be considered:
Number of HID lights — add 5% per air cooled light or 10-15% per non-air cooled light.
CO2: add 5% for rooms with CO2 enrichment
Filters: if a carbon filter is to be used with the exhaust system then add 20%
Ambient temperature: for hot climates (such as Southern California) add 25%, for hot and humid climates (such as Florida) add up to 40%.


An Example
In our 8' x 8' room we have 2 x 1000w air cooled lights, and we plan to use a carbon filter. We also plan to use CO2 in this room. The ambient temperature is 90 °F (32°C), however, we will be using air from another room that is air-conditioned. Here's the minimum required CFM to ventilate room:
1) Calculate the CFM required for room (see above.)
2) Add 10% (for 2 air cooled lights.)
3) Add 5% of original CFM calculation (For CO2.)
4) Add 20% of original CFM calculation for Carbon Filter.
5) Air is coming from air-conditioned room so no need to add any other percentages.
6) CFM = (171 CFM) + (171CFM x 10%) + (171 CFM x 5%) + (171CFM x 20%) + ( 0 )= 231 CFM.
This is the absolute minimum CFM required to ventilate your room.
The next step might seem to match the closest fan to this CFM. However, for this example I'd choose a six inch fan with a CFM of around 400 or more, and a 6 inch carbon filter to match. The extra CFMs may seem a bit excessive (calculations on most indoor gardening websites would recommend a 4" fan and a 4" carbon filter) but it's always better to over-spec since we need to compensate for air resistance in ducting too.
Also, as we are using a carbon filter we will need to match the fan with the filter so that the fan that will neatly fit onto the filter.
If all the variables are kept the same and we changed the room size from 8' x 8' to a 12' x 12' then the minimum required CFM would be 519 CFM.


The All-Important Inflow!
An intake port can be anything from a gap under the door to an open window - even a hole in the wall. The best place for an intake port is diagonally opposite from your exhaust fan; that way, air has to pass across the entire room - very efficient. You can put a piece of screen over the opening to keep insects and animals out, a piece of A/C filter to keep dust out, or a louvered shutter or backdraft damper that opens when the fan turns on and closes when it turns off. You can also use a motorized damper. This gets installed in-line with your ducting and is plugged into whatever device controls your exhaust fan. When your fan turns on, it allows air to pass. When your fan shuts off, it seals completely, preventing CO2, air, etc. from passing. You can get creative with these devices and use one fan to control two rooms, etc.
One additional note about intake ports - you will see much better results from your exhaust system if you install a second fan to create an active (as opposed to passive) intake system. Normally, when your exhaust fan sucks air out of your room, air is passively going to get sucked back into the room. By installing a second fan on the intake side, you will reduce the amount of negative pressure created in the indoor garden, thereby cutting down greatly on the amount of work the exhaust fan has to do and allowing much more air to pass through. If you're not sure or you don't want to spend the money, start out with just an exhaust fan. If it's not performing as well as you thought it would, try adding an intake fan - you'll smile when you see the difference!

Click to expand...

Sticky please!

the biggest fan u can get is a windmaker for the movies ...................basically it is air plane engine on mounts with a gaint prop .................u can get wind speeds of 130 plus

so the answer to your need for alot of speed ............take a lawn mower and rework it change the cutting blade for a fan blade (the hard part is balancing) i could look into a spare engine for a air boat

legallyflying said:

ok, well post a link from some site about growing saying that you need 2x the volume per minute.

Click to expand...

Easy...go to Icmag...way better then this place.