I looked up my area's average temperatures and found this: Daily temperatures rise above 85' on an average of only one day per year and fall below 23' on an average of only 2 nights per year. During the winter, the average daily high and low temperatures are 47' and 38', respectively. The summer months are equally mild, with an average high temperature of 68' and low of 53'. With this info, do I still need a complete air exchange once per minute? I've read both of your responses and now wonder if I have an exhaust fan in the upper north gable end set to come on at temperatures above 80', and have 4 automatic vents on the lower opposing side windows, as well as the screen door opened in the south side shouldn't that be sufficient airflow in my moderate climate? I'd like to stay away from the automatic roof vents because they seem to fail so quickly, much faster than the ones in the side windows. And, what temperature am I aiming for? Is about 80' good for my peppers and tomatoes and for my seedlings? I am still eating lettuce from last fall's outdoor sowing, so I don't expect to need much extra heat in the greenhouse in winter. (Sorry, I just love to brag about my winter lettuce!) Again, thank you for your advice. I just want to do this right the first time.

Interesting. Based on the pictures, yes, you have installed the blade backwards (the setscrew should be the other way on the motor shaft normally). Fan blade leaves have "pitch" (angle) in order to push or pull air, in addition, each leaf has a curve (concave or convex) depending if the fan is to push or pull. The picture seems to show the curve of the blade leaves are designed for pulling of air. So when you flip the blade, (as shown on the pictures) and the motor is rotating CCW, the air is being pushed efficiently out. Before you flip the blade, the air was still being pushed out, except the push was very inefficient because the curve was the wrong way. It appears that the blade is made for a fan intended for pulling air for a motor running CW, as in airplane engine, which is not very common. ItÂs possible that in the factory things got mixed up. dcarch

Well... Ambient temps have been hitting triple-digits here this week (FINALLY! We've got minimal humidity [Plus a swimming pool] so *I* love it!). I've eliminated the self-opener on the roof vent and put 60% shade-cloth on the entire roof; entire south-side; and 3/4 of the front (East, blasting-morning-sunshine) side of the GH. I've also drilled a series of (so far, 6) 3" round vent-holes (covers are appx $2-3 @ from Home Depot) along the bottom back-side of the GH. I drilled the wooden base with a hole-saw and I'm keeping the "plugs" so I can remove the vents and replace 'em with the plugs in wintertime. I was hoping to generate some cross-ventilation: Cool bottom backside air sucking in, and blowing out the hot front-side top. Nice theory but... After doing all of that, the GH *still* seems to want to stay 20* above ambient (today it was 122* in there! Ouch!!!). So I definitely agree with CR's assessment that 251 CFM is insufficient! To be honest, when I had no "lower, passive vents" and was relying solely on the roof vents, fan, and open door (and Bugs Galore!) - I got the same result (+20*). Adding a second solar fan is not an option. The panels only put out about 1.5 amps (max), and the fan seems to draw 1.2 amps. I don't have room for more panels (and I'm hesitant to cut holes in any panels, anyway). I'm still 'tweaking around' with it at this point. And this *probably* isn't the best time of year for this kind of "experimentation." I really don't plan to use the GH in summer ayway, but I still want to get a sense for "When I do this, That happens..." I'm sure any knowledge gleaned will come in handy for when I *do* have plants in it. My big challenge will be the "Tween" Seasons. Late Fall and Spring. Too cold at night to leave the plants out, but still sunny + warm (hot?) during the day (I'd hate to roast 'em! But I'm also too lazy to be dragging plants in-and-out every day!!!). It's definitely still a Work-In-Progress! And I'll keep you guys apprised of my progress (or lack thereof! ;-) Oh, Good News: My Freeservers Site is fixed, so the GH/Solar Fan Page has been moved back to where it belongs (new link below, and I'm still updating it) Thanks - AGAIN - for all the feedback! -Nancy Here is a link that might be useful: 2007 Greenhouse Solar Fan

I have a HFGH that was put up in April of 2007. There's a small wall type propane heater that does a nice job. Now I have an idea for a "Greener Heating System". What I'm thinking of doing is burying 4" PVC pipe in the floor with one end extended up to the peak of the greenhouse and the other end at floor level. The plan is to have a small fan blowing the hot air from the roof area into the PVC piping in the floor. The floor, that is now dirt with a layer of crushed stone on it would act like a big heat sink. Has anyone out there ever tried this? Any comments or suggestions would be appreciated. Thanks in advance. Joe Here is a link that might be useful: My HFGH