Greenhouse questions

I'm finally getting close to having a greenhouse built. I've got various questions that I would really appreciate any input on from people that have real-world experience. Many of them have to do with my deep fears that the Oklahoma weather will be a disaster if i don't plan for major cooling. I'll probably get a passive gas heater (southern burner). The gh will be 8' x 16', cedar, with a tall peak. Any input or advice on the following would be greatly appreciated:

1. Motorized vs. passive intake vents: I’ve always thought that with a high peak and a decent exhaust fan I could get away with passive ones. I’m probably going to have limited electrical outlets although I could conceivable change that. Related to that….
2. Number of electrical outlets: my site already has one coming out of the ground. My understanding is that you can add multiple boxes on one circuit but I’m a bit worried that one circuit won’t be enough. I anticipate an exhaust fan and a couple of oscillating fans and a pump or two for a wetwall and a misting system. Since the pumps would be intermittent, I wouldn’t think that electrical load would be too great. But then I’ll probably want/need lights.
3. Single vs. double door: originally I planned on two doors like a French door but for cost savings and since the overall size isn’t that great, I’m wondering if one door might be enough.
4. Solar roof vents: I’m assuming the ones with wax or oil in the cylinders are fairly standard and would plan to have at least two or maybe four to work with the intake vents to exhaust hot air from the top. Any thoughts on that?
5. Slab only vs. slab with gravel: I believe the contractors are planning on pouring a slab largely because the minimum concrete load is 3 cubic yards and they’ll have to pour footings. So they say they might as well use the extra for a slab. I assume that could get pretty slippery so I’m thinking pavers or gravel on top if needed. Also for humidity I wonder if the slab getting wetted down would be as good as gravel?
6. Exhaust fan vs. passive air flow via root vents and intake vents: with a high peak I wonder if I could get away with not using an exhaust fan? Since it routinely gets over 100 degrees here in summer, it worries me overall. But it does seem like the convection might be enough by itself.
7. Twin-wall panels vs. triple wall: I could save a lot of money by going with twin wall but I wonder if I would just be trading the cost of extra heating/cooling. Also I could kind of mix and match, i.e. put triple wall on the top and west and north, where extra insulation would be a benefit, but that would complicate things a lot. Related to that…
8. Panel attachment with screws or with H/U-channel fittings: the contractor wants to use the fittings but that will add a major cost factor and will get really complicated trying to determine the length and quantity of each type of fitting. I have a book on building greenhouses and it says to just screw the panels to the frame. I would think doing that with maybe some adhesive along the edges or weather stripping would be a lot cheaper, maybe stronger, and easier, and might actually look better.
9. Wet wall vs. aquafogger or other type of cooling: I definitely like the idea of the wet wall but it adds a lot of complications, including I would probably have to build it myself (the contractor has never built a gh and has no clue about a wet wall). I do think some kind of cooling will be an absolute must. I’ve read some forum posts where people really seem to like aquafoggers.

Again, thanks to anyone that takes the time to respond. I know everyone is busy and these are a lot of questions. But this is the time for me to figure a lot of things out and avoid major problems in the future.

 

Thanks guys. I showed the contractor one from a catalog that is from cedar. I think that's the main reason he is suggesting it. I had thought pressure treated lumber but from what I gather the cedar should last plenty long enough. I'll probably move before it rots either way. Plus it would look nice.

I think I'm convinced about using the fittings rather than screws. I have a book that says to just use screws but more than a few people have suggested against it. The bar fittings are damn expensive though! Not to mention the complexities of figuring out how many and what length to get. I always hated math...

And I'm now thinking a swamp cooler may be a smarter way to go vs. a wet wall. Probably more up front cost but should be a lot easier in the long run. One complication to the whole thing is I won't have a water source plumbed in. There is no reasonable way to do it since the closest water is on the other side of the yard and on the other side of a concrete patio, etc. So i'm going to have a hose bib installed and just hook up a hose. I haven't done any research yet into swamp coolers so any advice on those would be highly valued.

And I think i'm convinced about the value of extra circuits/outlets. I was hoping to save some $ on that but in the end, it would likely be worth the extra expense.

Still not sure what to do regarding solar roof vents. If I go with a decent exhaust fan it will probably be overkill to also have roof vents at the peak. I'm too lame at math to figure out how tall it will be. The walls will be 8' and the roof supports will also be 8' and the width will be 8'. Gotta be over 12' and maybe 14'? Pythagoras probably knows.

It'll have a drain on one end. I plan to re-use as much stuff as I can from my indoor setups. I have a ton of 4' light fixtures and two misting systems plus a lot of wire grates I can use for hanging things. From what I gather, under bench misting is the way to go for humidity. I guess watering will have to be done by hand.

 

Yea, it would be nice to do that but realistically, I don't have the time for it or any good way to find out who/where they are. The construction is due to start well before I would be able to get back into our local society. Also I tried before to get some advice from them and couldn't even get them to send out a mass email.

I'm in central Oklahoma where the humidity is a LOT lower than in the eastern regions. So I think a swamp cooler might be a good idea. However I did some checking last night and one of the right size would probably be around a thousand bucks or more. The money isn't such an issue, but I can't help wondering if I could create a pretty awesome wet wall for that kind of dough? Seems like the much larger area of cooler air coming in would be a big advantage as compared to the relatively concentrated ducted air coming from a swamp cooler.

What about a window unit AC? I realize the whole point of an AC is to remove humidity from the air but since it would be pulling the humidity out of the *outside* air and pushing it into the gh, I wonder if it would be a good option since theoretically the air inside would still maintain decent humidity. thoughts? tyvm

 

I do have a Sears! I googled swamp coolers and spent some time on Grainger's website. Apparently they have a store just a few miles from me. But yea, I was thinking I should definitely check out Lowes/Home Depot.

Msaar, I'm going to need an exhaust fan and shutters regardless just for general ventilation so I wasn't figuring them into the overall cost of 'cooling'. I figure they'll do double duty on that plus a swamp cooler or wet wall. Greenhouse megastore has some pre-made wet wall infrastructure. I haven't really dug into them too much yet though. Here's a link: http://www.greenhousemegastore.com/...t-system-4-inch-x-12-inch/evaporative-cooling

Marni, it will be oriented so that the long wall faces west. The long east wall will be pretty meaningless since the neighbors fence will be just a few feet away. The north and south walls will be the 8' ends. I'm imagining either a swamp cooler or wet wall being on the East wall or North wall. I envision most of the mounts and coolish/intermediate plants being on the north end. The house will sit under 60' oaks and my yard is surrounded by them on all sides plus three in the middle. So I'll have no shortage of shade. I think it should be fine for Angs, not so much Catts and Vandas. Good thing I don't grow them!

 

Have not done any kind of layout for benches. I have a fair number of potted plants but by far the majority are mounted. I figure I'll just wing it on the benches probably using concrete blocks and plastic coated metal closet shelves.

I'll need the exhaust fan to get the hot air out! It gets bloody freaking hot here as you know. And when it isn't hot, it's still hot! Today is unseasonably cool at 88 degrees. With such a small house, I can't imagine things surviving long without almost constant evacuation of the hot air. And if I have to be gone for a few days or if the swamp cooler goes kaput, an exhaust fan would be my only hope. Do you see a scenario where I would *not* need one? I'm all ears...

And i'm giving up on the wet wall idea officially. If I can just figure out the damn panels I'll really be making progress. I can find 10mm twin wall panels but haven't found (so far) the fittings (in aluminum) for that size. I'm tempted to try (again) to convince the contractor that some wood strips could be used to essentially clamp the panels to the house. I really don't want to use 6mm panels and I would really like to use three wall or even five wall but the cost and the fittings are problematic.

 

Yea, everything you said makes sense. My impression is that the main reason would be just the degree of heat I'll be dealing with coupled with the small size of the gh. For instance, last year we had temps over 100 for something like 90 days including some days over 112. And overnight temps won't go below 80 for a month or two in the summer. (that's probably indicative of why there are no orchid nurseries in Oklahoma!). Maybe Robin will see this and chime in. He deals with temps that are nearly as bad as here and has two exhaust fans. Of course he *does* have a wet wall. So in the end, it is all very confusing. Where is that head banging on a wall emoticon when you need it!!??

I think i'll end up going for a swamp cooler, two passive roof vents, two wall intake vents and an exhaust fan. I'll use misters to wet the floor which will be gravel over concrete or a combination of bare concrete and some gravel where the misters will be. Hopefully the evaporation from the floor plus the cooler will be enough. I guess in a pinch I could get two swamp coolers. Just today I found a local distributor for polygal panels which should be a big plus. Thanks to all for your help.