help me understand ventilation math (400w in 2x3x6)

Kaban

Kaban

Member
Hi,

I'm trying to understand CFM and how it relates to noise and fan size. I plan to build 2x3x6 (36 cuft) grow box/cabinet and have already bought a 400w hps (not cool-tube). The cabinet will be in a room that has AC.

1. How much CFM would I need for that space? Is there a rule like "all air from the grow box must be recirculated in x seconds"?

2. Do two 100 CFM fans equal one 200 CFM fan? Will they be more quiet?

3. I can build the box shorter or taller. How does the volume of the box change the ventilation requirements? (IIRC 400w light is enough for at least 9 sq ft)

4. Money-wise, is it cheaper to build proper ventilation for 400w or downgrade to 250w and ventilate that? Or to 150w? How do ventilation requirements change with wattage?

Thanks in advance. If there are no exact answers, I'm cool with doing trial-and-error.. just thought I'd ask first ;-)

Kaban
 
Green Cross

Green Cross

Well-Known Member
Kaban said:
Hi,

I'm trying to understand CFM and how it relates to noise and fan size. I plan to build 2x3x6 (36 cuft) grow box/cabinet and have already bought a 400w hps (not cool-tube). The cabinet will be in a room that has AC.

1. How much CFM would I need for that space? Is there a rule like "all air from the grow box must be recirculated in x seconds"?

2. Do two 100 CFM fans equal one 200 CFM fan? Will they be more quiet?

3. I can build the box shorter or taller. How does the volume of the box change the ventilation requirements? (IIRC 400w light is enough for at least 9 sq ft)

4. Money-wise, is it cheaper to build proper ventilation for 400w or downgrade to 250w and ventilate that? Or to 150w? How do ventilation requirements change with wattage?

Thanks in advance. If there are no exact answers, I'm cool with doing trial-and-error.. just thought I'd ask first ;-)

Kaban
Click to expand...
1. Every 1 - 5 minutes, and it's better to be on the safe side.

2. yes and no - 1 + 1 = 2, but 2 is louder than one.

3. More cubic feet will require more ventilation.

4. 250 is easier and cheaper, but you get what you pay for.

Just build it
 
R

rreign

Active Member
You can do it way easier than all of this. Just go to Stealthhydroponics.com then click on the FAQ on the right side of the page. The first thing on the FAQ is a calculator for CFMs, Watts, PPMs, etc.
 
You must log in or register to reply here.
Top