ventilation help

Hey all. I'm new to indoor growing. Trying to design a grow sset up. I have a twelve by eight total floor plan. An 8x8 flower room with 2x600w in half the room and the other half work space. I plan on partitioning the other 4x8 section will be a veg room. I have a passive intake on the floor that allows air in from an adjacent bedroom. How big of a fan will I need? I was thinking of running one ten inch hooked up to a roof vent in each area? Will this work? Should I get a bigger fan? I was planning on running the fan at 20% constantly and have a temperature overide to kick it into full spped? Input?

Are you saying that you will not have a dedicated ac and dehumidifier for this room? That's a lot of space and wattage or what you are asking.

figure out how many cubic feet is in your room, multiply that by 5 and you get the cfm rating of the fan you should be using. good luck!

drolove I have to question you on this. I thought you wanted to exchange the air every 5 minutes, not 5 times a minute.

[FONT=Verdana,Arial,Helvetica][FONT=Verdana,Arial,Helvetica][FONT=Verdana,Arial,Helvetica][FONT=Verdana,Arial,Helvetica][FONT=Verdana,Arial,Helvetica]A C+P off the web 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.

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so aparently people disagree on whether it should be every 3 or 5 minutes. either way exchange that air