Ok, this is what Dale told me from another post when I described the washtub I'm currently using for a vent hood: IT goes like this 16.5x32.5=536.25 square inches. Divide that by 144 (one square foot) you get 3.75 square foot opening. Simple ventilation rule is a minimum of 100 cfm per square foot of opening. So your 3.75 square foot opening requires a fan of 375 CFM... Probably a 400 cfm fan would be even better considering losses in fan efficiency and duct work...
This is the NEW fan I found at a very reasonable price:
<img src="http://us.st11.yimg.com/us.st.yimg.com/I/californiahydro_1946_333632" border="0" alt="" />
Here is the info: Popular 'squirrel cage' fans, technically known as shaded pole blowers, quickly exhaust stale air out of hobby greenhouses and growrooms while bringing fresh, clean air in. Mount securely to wall or ceiling. All sizes are now compatible with Hydrofarm® Super GrowWing and Radiant Reflectors for the ultimate in room cooling. Quiet, powerful performance; exclusive dryer hose adapter flange; safety intake grill; grounded 8-foot heavy-duty power cord. Instructions for horticultural use included. UL and CSA Listed. Figure size needed for general room exhaust by taking cubic feet of room and dividing by 5. Fan with cubic feet per minute (CFM) rating just above the result will completely exhaust stale air in 5 minutes as recommended.
QUESTION: Does this look good? I can get it in 465 cfm, 600 cfm or 800 cfm. Which one would work best?
Thank you very very much!!!
Alexis