Greenhouse Univent Window Opener

Not yours, your seedlings'. If you're getting your first coldframe or a simple greenhouse, you really need an automatic vent opener. Unless you are in your garden religiously every day, there will come that unexpected warm, sunny day early in the season when you'll forget to prop up the lid on the cold frame. You'll come home to find all your lovely, tender seedlings, with all their promise of bursting youth and color, lying limp and toasted and very dead all across your six-paks. Six weeks of careful tending and happy anticipation ruined in a moment. Some gardeners never recover.So save yourself the heartache and get an automatic vent opener. I've used the Univents and they are very dependable. They work off the temperature of the air, which causes the oil in the black cylindrical cartridge to expand and push forward the piston-rod in the cartridge. No electricity, no wires, very simple, very little to go wrong. Installing one can be confusing to figure out, mostly because they are designed to work with so many different possible vent configurations, but some staring at the (small) drawings for awhile will provide necessary clues. Once you understand what goes where, the actual installation is pretty easy.One other nice thing about the Standard Univent is that you can easily unhook it from its lower bracket (the one on the coldframe wall), so you can swing the lid up completely free and have full access to the interior. Very quick.I haven't used any other kind of auto vent opener so can't make any comparisons, but the Univents have been very reliable.

I've had one of these (same brand, from Denmark) on a no-name greenhouse in our yard for years and had zero issues. So when we built a Grandio Summit greenhouse, I tested one unit bought here on Amazon and found it does fit using the Grandio hardware system (so I purchased 5 more). Use the same little hex-wrench connectors that are intended to attach the manual vent opener from Grandio on one side (the window side), and then use the standard Grandio bolt/nut connector on the other side (lower side of vent opening, where the detachable bracket goes). It didn't quite seem to fit at first when I pressed the window shut during installation but it seemed once these opened and closed initially it worked better. If you have clearance issues with one arm hitting lower frame of the window opening (possibly keeping the arm from opening the vent completely) try trimming off a little point that sticks out on the end of the opener arm, by using a hacksaw or tin snips. I did that but now I'm not sure it was necessary. Long story short, these will work with Grandio greenhouses, and they are almost half the price of the openers which Grandio offers for sale. If you need 6 or 8 of them that's quite a savings.

I bought this Univent roof vent opener from Agricultural Solutions because the Palram opener I bought with the greenhouse last year failed. The Palram said to take it off for the winter if you have a heater in there & don't want it to open & let the heat out. When I put it back on in the spring, the piston leaked & didn't work. I couldn't get a response from Palram. They don't sell replacement pistons.This Univent opener doesn't need to be removed for the winter. Its easy to unhook the bottom so it doesn't work if you want the roof vent to stay closed. It also came with a velcro strap to hold it closed in a windstorm or for some other reason. It was easy to install. I used the brackets leftover from the Palram, so I didn't need any other adapters. I also like that I can order replacement pistons if they do fail. I've only had it 3 weeks, but so far I think its a good product.

I bought two of these units, and they worked great for about six weeks, then failed. The "t" bracket at the end of the piston plunger mounts into holes on the 2 main brackets. After the holes were drilled, there was less than 1/8" of aluminum left on the sides of the brackets to give the bracket strength. After 6 weeks of wind vibration, this bracket wore through, and both brackets broke at this stress point, making the whole unit useless. Also, all the aluminum brackets on the device are held together with aluminum rivets, so there are potentially 4 different points where these brackets can fail due to vibration.I repaired this device by drilling out all rivets and replacing them with stainless bolts and lock nuts and cut two pieces of 1 1/2 inch wide aluminum stock, (at a 45 degree angle) about 4 inches long, and bolted them to the broken angle brackets with 6/32 x 3/4 inch bolts with lock nuts. I re-drilled the hole for the "t" bracket in the new stock, and now the unit will hold the stress and vibrations of any winds that tend to flex your open top. I also attached an 18" long piece of aircraft cable from the base to the door, so that wind will not extend the bracket beyond its maximum expanded length and not place undo torque on the device if a gust tries to force the top open. I also placed the small pin that holds the "t" bracket to the plunger with another small bolt and nut. Parts cost me about $5 at the local hardware store. The seller, Potting Blocks, has contacted me and has reimbursed me for the purchase price. He told me he will contact the manufacturer, J. Orbesen Teknik in Denmark about these defects and will see if he can also start sales with an optional, more durable, galvanized and stainless steel version of this opener, which are also in their product line.