Buying a greenhouse kit

I finally can find a space for a real greenhouse. The Idea is to use it in spring for starters and early greens and in fall for greens and potted peppers and tomatoes to supply us with fresh veggies while they can survive in there. After some research I fixated on this greenhouse. What I like about it, it is polycarbonate, so it is somewhat insulated comparing to film. Also they provide all accessories I was thinking about. I work, so my main problem in spring is when to open the greenhouse. When I leave to work it is too cold. But on a sunny noon it can fry my veggies if closed. I was thinking automated fan or window openers. They offer both.
So I try to figure out what is the minimum set I need to automatically hold the temperature. Greenhouse comes with 4 roof windows with manual openers. I want to go with 7X14 greenhouse.
There complete kit includes following above a base kit:

  • 4 Automatic Window Openers
  • 1 Louver
  • 2 Solar Powered Thermostatic Fans
  • Full Size 2-Tier Aluminum Shelving (top & bottom shelves, for one side only)

I definitely skip the shelving, but the rest I need some advise. I like the idea of Thermostatic Fans and automatic window openers, but do I really need a Louver? They are not automatically opening, so if I need more ventilation manually I can open the door instead. And speaking of the door - they offer second door kit , should I install second door? Anything else I am missing?


I’d say you definitely want some kind of air intake near ground level. I don’t know about that type of solar powered fan, but you’ll probably want a fan that can move at least nearly the entire volume of air every minute or so, especially if you’re planning to keep anything in there in or near summer. You want the new air to come in as low as possible to get the air currents flowing effectively. You also don’t want to have both roof vent openers AND an exhaust fan, only one or the other (I recommend a fan).

For my greenhouse, I find that even with a 12x12" louver and a fan that moves about 0.85 air volumes per minute, it gets too hot by ~June if I don’t also open a door next to the louver.

For reference, my greenhouse is 21’x14’ and 9’ tall at the eaves to 13’ at the roof peak, and we generally have a pretty low sun angle here in Seattle vs anywhere else in the lower 48.

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I thought both automatic openers and fan in precaution. If the fan battery dies, the openers still will work, as they are mechanical(are they?). Will the door serve the purpose of the louver? What about two doors?

The problem with having both is the fan ends up pulling new air from the nearest other opening, and if that’s in the roof then the rest of the air volume isn’t actually getting replaced. In other words, the air flow is what is shown red here instead of the blue, what you want:

And yes, they are mechanical if they are the kind that use wax cylinders.


Got it. So I guess the secure way would be to have them, but not to use them, if the fans are in working condition. Is there a way to turn them off without damaging?

They can be adjusted by twisting them, and you can also remove the wax cylinder entirely to convert them into manual hatches, which is that I did for my roof hatch. You could twist them to the highest temperature in their range so they only open when the fan is already not doing a great job, but I do think you’d want to open the door or doors in that case, too.

There was some great input from other forum members on heating/coolinga greenhouse in the thread I started for my greenhouse awhile ago:

Can you leave your greenhouse unattended for 8-10 hours? I think I started to understand a purpose of the louver. I close it for the night, and open before going to work. The cold air that will go in is not going to get up to the plants, if they are raised on the tables and shouldn’t affect my heating very much while it is too cool outside. But as soon as temperature start raising, heating will turn of and fans will start to blow when temp reach the “hot” mark, At this moment louver taking air near cold spring ground should help cool the space off. And door will make too much cold air getting in while heat is still on. Thanks! So, no to automated openers, and yes to louver!.
Thanks a lot!

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For mine, the fan pulls it open and then it swings closed when the fan turns off, so there’s no manual opening or closing required. Once the overnight lows are warm enough in late spring or early summer, I stick a strong magnet to it to hold it open 24/7, because the fan only pulls it about 2/3rd open, so that improves air flow.

Mine is pretty fully automated for heat management, but I do manually tweak things a few times each season. I have left it unattended for up to a week, and up to a month with someone coming occasionally to water things. I replace the glass on one of the doors with a screen during summer months to avoid having to manually open a door.

Also by this time of year the fan never runs and the vents are closed all day, so there’s not really anything that needs to be done. Here’s what the temperatures have looked like for an unusually sunny week (you’ll notice the saw pattern when heaters kick in below 45°F):

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Thanks! How strong your fan is? They recommend 2 fans they selling per 7X14, they do not give exact parameters of the fan, but saying it can cool 5-7 cubic meters. But if I roughly estimate the volume of the 7’X14’ it is closer to 16 cubic meters, not 10-14. So 2 fans will be not enough…

Mine is this one (18" and 2000 CFM, in case it defaults to a different size):

I got one without the manual speed adjuster, and I just plug it into one of these to turn it on and off:

Don’t go cheap on your greenhouse, especially the ventilation.


yeah, that is great… I am just not sure how I will install it on the poly panel. It looks heavy. And going with building my own structure may be better and cheaper, but I can’t do it myself and put another project on my husband’s list doesn’t feel fair. I may get three recommended fans instead…That also will bring more overheat security - not all of them get out of business in the same time :smile:

Those aluminum greenhouses are very fragile.

All of them? Can you be more specific, what exactly happens to them? Wind, snow, anything else? They saying these built by European standards and can hold up to 15 inches of snow. There are also options for storm kits.

I have seen a lot of posts about panels popping out in wind. aluminum support posts !5 inches of snow is not much load. Snow is fluffy and light. A good 60 MPH wind will put on more stress than that snow will. Be prepared to Anker it down to a significant foundation.
Here is mine. It weighs about 1500 pounds. It is 4 layers of glass thick with a 5/8 inch air space between each sheet

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yes, I am planning to make pressure treated 6X6 foundation, connected to the ground by deeply inserted anchors. The aluminum base will be connected to it. They also sell storm kits that can be installed inside the greenhouse before the bad weather.