The sun wont burn them, but the heat generated by the sun can if you have no fans running. Keep the air moving. If shade plants, then you'll need some kind of shade-cloth.

The sun can burn them. I have a glass GH and I find that the most problematic times of the year are spring/fall, when I'm in transition between shade cloth in summer and the extra layer of poly I put up in the winter. What I eventually have started doing is to move DIRECTLY from winter poly layer to the shade cloth in the spring, with no period of unfiltered, unshaded sunlight in between...opposite in fall.

fwiw, I agree with stressbaby. I too have a glass GH. I was surprised to find the burn damage that occurred during my first spring. It was completely unexpected because the temps were so were so cool. Ventilation is crucial too, but I suspect you'll need shade cloth.

Do you have insulated glass on your greenhouses? My main south wall is insulated house type windows. would that help me from burns? Also, i won't have established wintered over plants or use poly at all to insulate so they will be new starts out under full light this spring. Will that kill them? i'm in zone 6 western kentucky

Last year I noticed Wal-Mart was selling shade cloth for patios. I would invest in shade cloth and cover the top. If your east and west doors open, you can open them for cross ventilation. Buy a box fan, drill two holes at the top, use short eye bolts, S hooks and a chain to hang it at the top of the door to out-vent hot air. You can buy 120V thermostats at the big box home improvement stores for around $25 to control your fan.

I understand the shade cloth for the top, And will probably get one for the top for summer. Also my front windows will all open 1/3 if the way and have house screens on them. So that will create a little light diffusion on the wall.they will also open at the highest point in the greenhouse and also in the middle so i have tons of big vents if needed. i will also have a window in the lower back wall so i can have updraft venting. also the entire bottom 2 ft. of the long front/south wall will have cold frames along it that will also open up. I really like the box fan on a thermostat idea. I'm trying to save money on it for sure. After tomorrow it will be 90% done. i'll post some pictures of it saturday. its actually pretty cool looking...lol

crabcat,

Yes, I have dual glass in my greenhouse. Without knowing exactly your lighting conditions, its pretty hard to predict what your results will be, but I think you will find that improving your ventilation, while important, will have little effect on whether your plants will burn or not. Likewise, air temperature can fool you. As I said, I found out the hard way that nice and cool spring temps did not prevent plant burns when the sun is bright.

I love glass, but it will focus the available light while other options will diffuse it.

Hope this helps.

I appreciate the responses, i do have another question. Where my green house is located and its roof being pitched downward away from south, most of all my light will be coming in my walls and expecially from my large south wall. the sun probably won't be over my roof until most of my spring growing in the greenhouse is over. Can i use the sunscreen inside as a inside wall curtain or does it have to be outside...same with my roof in the fall, can i hang it inside?.. And should i get a 30 percent for my veggies? Keep in mind i never have all day full sun either. My cold frames, single pane glass,located in the smae basic area have never burned up my plants and my greens in my frames even made it through the latest 8 degree nights/20 degree days. I will also post pictures tomorrow afternoon. it should be done by then.

My shade cloth is inside. Prob not as efficient, but it keeps the horrible winds we have from ripping up the expensive Aluminet.

Single pane tempered glass GH here.

Another option, and one available only to those with glass GH's, is old fashoned but still available and quite effective whitewash. Along with the fact that it won't blow off in high winds, it's most useful feature is the ability to create as much or little shade as you want, where you want it. Just adjust the amount you lay on any particular section. You could even use blue tape to create latticed shade.

Here is my greenhouse. The wood walls are poplar that will be stained a dark green. the rest of the windows except for the small ones in front are double pane vinyl sliding doors. The bottom row of small windows will be leaned out and made into a coldframe when done. The inside will be stained white. The roof is super high quality Anderson vinyl doors with 2 feet of solid roof on the bottom part to take up the exrta roof the doors don't cover. I have three barrells buried down a foot in the front for my first shelf to sit on and so i can have more shelves. The 4 big windows up front have screens on the ends. The floor will be wood pallets right now till i can afford something better and the back wall will be insulated also. any suggestions people.?
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With the wood framing and vertical wall, four, 4 ft. white vinyl blinds, trimmed at the home center to fit perfectly between the studs would be fairly innexpensive and give you easily adjustable shade.

Even when all the way down with the slats tightly shut, a lightweight white vinyl blind will still admit quite a bit of diffused light and with the slats opened a bit and turned up, a lot more, but still prevent leaf burn from direct glare.

Great, that's what i was hoping for. And if they warp or wear out i can cut them up and re-use them as plant markers... Another thing is at night closing them all the way will keep my plants along that wall from getting chilled from the glass and also prevent a bit of night time heat loss.Most of my plants will be along that wall. they would also open enough for me to allow my windows to be easilly used. I will also need some kind of inexpensive suggestions for the roof. I would like to put some kind of shade cloth on the underneath side of it during the summer so it lasts a long time, and also something that would not trap moisture.. I guess i could go ahead an spring for some mesh type cloth if i have too unless somebody has some frugal ideas. Can i use 30 percent cloth? i want as much light as possible. It does get very hot here july, august and sept. And I really do appreciate all the help and suggestions folks.

After I posted earlier, I went back to your original post again, then your photo, and realized that your GH will be 12 ft. long, not 16. My bad. Sorry, but does that mean the windows are more or less 2 @ 4 ft. and 2 @ 2 ft? If so, that makes the blinds even cheaper.

Winter insulation at night? Well, if you know you will be there to open and close them morning and night; why not yet another trip to a window dressing dept. for some cheap washable insulated drapes? Or, if you are as handy with a sewing machine as you are with woodworking tools, buy the fabric and whip them up yourself.

Insulating the back wall: 2 inch thick, Type 150 foam is one possibility. It's sturdy, waterproof, highly insulating and you could mount vinyl pegboard against it, to allow you to put shelves were and whenever you like, then move them at will, along with lots and lots of hooks, to hang all of the little tools you will be using around the GH and driving yourself nuts if you can't find just the one you want, when you want it.

A well organized GH makes using in it so much nicer, but you can't put tools back in their place unless they HAVE a place and it's a lot easier to find a particular one if they are all hung out in full view, as opposed to being piled into a box.

Been there and done that in our garden shed, then learned to love pegboard and- plastic slip ties, to make nice big easy to use loops by running it through those silly little holes mfg. put in tool handles, as if anyone had the time or patience to wrestle them on and off J hooks.

Inside my greenhouse I've used old bedding sheets (light colored ones) to protect my seedlings that prefer shade.
It may not be a long term solution but I have been able to use the same ones for a couple of seasons anyways.

Might make a cheap option until you find something else.

The windows are 3'x6' each. but the rough openings between the 4x4 corner and center posts are approx. 65" so 2-32" standard size mini blinds per side should work nicely. i was runnung short of funds, so i was going to put off the insulation until this summer, but i sold a 900.00 cat today so i can afford insulation now. i'm definatly going to use some rigid foam insulation. I already have quite a bit of closet type coated wire shelf system that i'm going to use as shelves along the front wall and sides. they are easilly adjustable. I scrounged these so they were some nice free high dollar items. I've already figured out how i can have the mini blinds work behind them. No curtains...good idea tho. A small piece of vinyl peg board above my potting bench on the back wall is a good idea also.

cute house! I still use pallets (on cinder blocks) as benches. shade cloth *outside* the greenhouse helps to keep the inside temps a bit cooler, but shade cloth *inside* helps to protect plants from harsh sun. I have an outside shade cloth over the top of my GH, but for one month a year I get the harshest afternoon light coming through an end-wall. This is also the end-wall with the big double doors, and by then I'm usually leaving them open all day (so not even any polycarb is blocking light), so I've hung a shade cloth like a curtain on the inside. That curtain is 70%. My regular cloth is 50%, which goes on by late March. Before then, if you want to shade delicate seedlings I generally use a medium weight row-cover, or burlap because it's used on what plants need it, not on the whole house. 30% sounds low to me, but you know your site best. Since you don't have a lot of space to cover, check out the shade cloth remnants at farmtek.com. I've gotten some seriously good deals over there in the closeouts section. I think that curtain remnant cost me five bucks.