You should be fine, it says it changes the air in a 10x10 room every 2.5 minutes. I use a 5" exhaust for a my 4x4 mylar greenhouse and it works great.

I can't decide which of these fans to get (remember this is for a 6x8 HFGH), the Canarm is $70.00 while the JD is $129.00. I want a fan that will do the job but not be to overkill.

Any advice would really be appreciated!!

Here is a link that might be useful: Canarm

Here is the JD VES10C Fan.

Here is a link that might be useful: JD VES10C

I hope someone who know will answer you. I have a 6x8 waiting in the box to be put together. Best of luck with yours.

I used the greenhouse fan calculator on this website, when deciding on the exhaust fan for my 10 x 12 greenhouse. It might be helpful for you.

The same site also has a heating calculator that can be helpful to walk through, as well.

Greenhouse fan calculator

Mudhouse's, I did see that calculator, thank you. Do you have the J&D Mfg 3 speed fan? How do you like it? Looks like I can get that in a 12" model that has 1100/850/550 cfm.

Mudhouse's, I did see that calculator, thank you. Do you have the J&D Mfg 3 speed fan? How do you like it? Looks like I can get that in a 12" model that has 1100/850/550 cfm.

It's been about 6 years now, and I don't see any manufacturer name on my fan (just checked.) But we bought the 16" three speed fan on the ACF Greenhouses website, 2950 / 2050 / 1200 cfm, for our 10x12 HFGH. I think that is the slightly larger version of the 12" size you are looking at.

It has worked fine, no problems. During the coldest part of the winter (when I don't use the exhaust fan) we cover the outside louvers with a wooden box my husband built to fit, to prevent losing warm air through those small gaps in the louvers.

I have not cranked through the numbers in the calculator for the 6x8 size greenhouse, but I can tell you I hardly ever operate my fan at anything but the highest speed. I thought I would want to use the lower speeds (a little less noisy than the highest speed) but I have found I need all the help I can get during our hot summers (we have some days over 100F here each year) so I keep it set on high.

I bought a plug-in thermostat from www.kkontrols.com to operate the exhaust fan, and that has worked fine too for six years.

I have gotten used to the sound, pretty much, but it is a bit of a relief in the evenings when the fan finally kicks off (silence is good.) I am sure my neighbors can hear the hum from a distance, but nobody has ever complained, thank goodness.

I am not a very good person to ask for advice about intake shutters, on the opposite side of the greenhouse. My (crude) method is simply to keep my sliding doors slightly open, with an aluminet shadecloth curtain clipped in place over the opening, as an air intake. Also, in the summer, I have screens in place on the south wall of my greenhouse, so air can get in that way, too. Other folks in this forum will likely have better info for you about ideas for air intake needs. I decided to start out simple, and never got any fancier with my set up.

Mudhouse, Thank you for the info, I was thinking that the 12" fan might be a little to big for my setup, but after hearing that you run yours on high I feel it is a good choice.

As far as the intake shutter I went with a 16" one with a motor, and of coarse a thermostat to control both.

The sad thing is that the fan and motorized shutter cost me more than the greenhouse did.

Here is a link that might be useful: I went with the VPES12

This post was edited by eastpenna on Wed, Apr 24, 13 at 14:45

I'm glad that helped. I know these decisions are hard when it's all new to you, and it was all new to me too. I felt kind of silly buying a three speed fan and then never using the lower speeds, but then again, at least I ended up with something that seems to do the job (coulda been worse!)

I know, all of my own greenhouse improvements cost me more than my greenhouse kit, too. But, I consider two things. First, without my exhaust fan, heaters, thermostats, etc., all of my plants would be dead, and then I'd have totally wasted my money on the greenhouse kit. :-)

And, second thing I tell myself is, if I'd had to spend thousands on a kit, as some folks do, I'd be even more in debt time I got done buying all the necessary improvements.

Also...having a greenhouse probably isn't the most profitable hobby in the world, but life is short, you'll learn a lot, and your family will always know where to find you. :-)