Personally, I wouldn't do it. Hail storms are tragic enough for us gardeners, and I just couldn't handle owning a glass structure and stressing about it every time the sky darkens. But maybe if you've never had severe hail there you are less likely to get nailed?

You might consider a polycarbonate roof and glass sides, but even that would probably be risky because rarely does hail fall straight down from the sky.

I used to live in Indiana while in grad school, and at least there the hail storms seemed to come out of nowhere, I dont know as you would have enough time to put a cover on before the hail started. We would get rain, then suddenly it would be much louder and there would be hail everywhere. And you def would not be wanting to have to toss a cover over the GH ever time there was a cold rain.

Have you considered using double wall polycarbonate on the roof and glass on the sides? I think this would be your best bet because the panels one the roof are the most likely to be broken by the hail, not the vertical ones. My family has several large greenhouses, some glass, some fiberglass, some polycarbonate. If i remember correctly you have to change the polycarbonate 3 times before the glass actually becomes cost effective.

What are you planning on growing? This may have a major impact on the material you choose. For example the chrysanthemums that we grow in the glass houses have smaller much darker green foliage, where as the ones grown under poly have larger and lighter color foliage. Personally I prefer the plants that have the larger and lighter foliage. There have been a lot of articles published on glass vs poly vs poly, and you may want to look at some of those. I think the real advantage of glass is when growing bedding plants.

Glass is the prettiest, but if you want a fully functional greenhouse with automation, you could probably take the savings that you would get with poly and get a control system that would open your windows, and buy a heater as well.

I have a glass greenhouse that has been through several hailstorms with no damage, although not as fierce as in your area. My greenhouse has tempered glass, so it can withstand pretty powerful hits. I'm sure at some point that a big enough hailstorm can shatter it, but I suspect it may actually hold up better than polycarb. I presume that, where you live, there are skylights around town that survive hail storms, and most of those are probably tempered or laminated glass. So you might want to consider the use of those materials. I would never have a greenhouse with just plain glass overhead for reasons of both hale and falling branches.

no glass in OK. As a fellow Okie i know the karma that comes with our spring storms and once you put up a glass house it will for sure coming hailing baseballs. Polycarb would probably be the best and easiest to replace if and when you had a piece get hailed..i mean nailed.LOL

I just had an idea. How about an outer wall of polycarbonate and an inner wall of glass? Does such a greenhouse even exist? Is something wrong with my idea? Experts, chime in please...

Thanks a lot for all the comments.

What do I want to grow? At this point I am ambitious - a four-season greenhouse warm enough to move my orchids out, grow tropicals, and also start and perhaps grow vegetables. But maybe I want too much - I'll have to investigate whether that is feasible with all the heating and cooling issues.

Indeed, one could say that since I've never seen big hail in the 11 years I've lived here, what are the chances that I would see big hail in the next 20-25 I anticipate being able to to stay in this house? And, if we got softball size hail, chances are that the greenhouse would be the least of my worries. Also, I do actually have a skylight in my house and I've never had a problem with it (not glass though).

As far as my covering idea goes - I was not proposing to put it up and take it down for each storm - that would indeed be difficult - but rather to leave it on during the storm season (March until it gets consistently warm). E.g., cover the roof, but not the walls, and lash it down well to the basewall (probably have some eyebolts or something put in the basewall for lashing purposes in general). I realize that if I did that, I would lose light, but light is something that it seems I have plenty of.

Ok, it looks like polycarb roof and glass walls might be one way to go, except I don't think that Florian does polycarb. Their catalog doesn't mention it, but I'll give them a call to make sure. I've seen one company that will mix media like that - Sturdi-built out of Portland, OR, but their greenhouses are wood and I don't think I want to deal with that.

Or I will make sure that it is tempered glass on the roof.

I went to the Florian website and looked at the Geneva picture gallery. Those are pretty greenhouses but most don't have exhaust fans, heaters, wet wall, or even much in the way of vents; all the things needed to make a greenhouse useable in a hot climate.

I'd also want some diffusion of the light not that clear glass. As pictured most of those greenhouses look like solar ovens.

My greenhouse has double poly and works wonderfully in SW Texas. Won't mind having poly carbonate roof. But that glass looks too clear to me. You'd almost surely end up with a shade cloth to make it useable and then it won't look so pretty.

In this climate a wet wall, big exhaust fans, and shade cloth are essential for summer use. My crops are fruit that will take 90-95F and I need all of the above. Most of OK is hotter than here at 4500 ft elev.

Here is a link that might be useful: Florian Geneva pics

I should also have noted that at least one layer of the poly should be IR. That's the kind that diffuses the light and reflects some heat back in at night. No clear poly except the top layer with IR below.

I had hail last year and the hail, although not too big, made at least 100 holes on the polycarbonate roof of our gazebo. The roof is tea color, two layers, with grooves in between the two layers. If that is what you say that is polycarbonate. I think that the tempered glass idea and fully automatic on everything is a better.

In our locale, GH (or skylight) roofs need to be tempered laminated glass. The same stuff car windshields are made out of. At least to pass a building inspection they do.

This makes glass GH roofs very costly. And some hail storms do still break car windows, so it is not an absolute guarantee.

My experience with 8mm polycarb twinwall is that is is quite tough. It has survived several hail storms (nothing bigger than 1.5" stuff), and had a large icicle drop from a second story gutter on it with no damage.

Yeah plus 1 on the tempered glass, just make sure to get a couple of extra sheets of it when its built or if DIY and save them in the attic or somewhere in case you get one or two windows broken.