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. [...]