Definitely use multiwall polycarbonate instead of glass as it will be a much better insulator than glass. The less expensive kits use 6 mm double wall polycarbonate because it is the least expensive of the multiwall polycarbonates. Here in Southern California I am using 16 mm triple wall polycarbonate. For your application I would look at using something like 12 to 16 mm quadrupile wall. You should be able to get good prices for multiwall polycarbonate in Ohio; there are a lot of distributors there. I bought mine from a distributor in So Cal and the order was shipped here FOB Ohio.

Mine is wood framed but there are places around the glazing sections where aluminum extends from inside to outside and I had to insulate those parts on the inside with 1/8" foam because water was condensing there on cold nights and dripping onto plants.

Ortho (garden products) has a greenhouse book that I bought at Orchard hardware. It has some good sketches showing some design and construction details.

When building a polycarbonate, wood framed greenhouse from scratch you will need to find a glazing system for holding the polycarbonate in place; that may be a bit more difficult to source than the polycarbonate sheets. It is easy to find aluminum extrusions for framing 6 mm but I had trouble finding something that I both liked and was not extremely expensive for my 16 mm sheets so I designed my own system from easily sourced materials.

Oooooo!! Good info! And yes, I also thought a one month's heat bill might be more than $1K. Scary.

Now I must run off to look at greenhouse kits. :D

This will give you an idea of what commercial glazing systems look like:
Polygal North America | Aluminum Systems | Mega-Lock Aluminum Glazing System

Now I remember one reason I decided to use my own system. The commercial aluminum extrusions were mostly only available in long sections, like 12-16 ft., which is too long for FedEx or UPS and instead would have to be shipped LTL on a truck.

I see on page 2 here:
http://www.polygal-northamerica.com/...ilesEn0107.pdf
they say that standard length is 6 meters (19 ft.).

I lived in Omaha/ Council Bluffs for about 15 years. I will be returning to the Midwest, but I think lower down, Springfield or Cape Girardeau MO in about 2 years. In Council Bluffs I saw a wonderful greenhouse attachment to a house. I would have loved to have one of those. First, because the heating and everything did not need to be separate from the main house. I love these attached greenhouses and really think that it would be a great observatory or tea nook in the winter months. For a modest 100 or so plants, this would be correct. Any more, I'd have to start selling them.

Good luck with the greenhouse! :)

Thanks for all the info, guys. It may be several years of planning before we break ground, so I think I will print this thread out to keep it handy! Lots of great advice here! :)

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You guys might enjoy my greenhouse dream page on pinterest. I keep finding all these photos of incredible antique conservatories and orangeries. These are the blueprint for my "won the lottery greenhouse". ;)

Views from the Orangerie on Pinterest

Another good book to check out is The Solar Greenhouse Bock. It's a very in-depth look into how to build a greenhouse to maximize solar gain and insulation, which lowers heating costs.

I've been researching for three years and haven't got my greenhouse yet :( Are you able to build a greenhouse attached to your house? That helps a lot in heating/cooling the greenhouse, and can also help heat your home in winter. Plus the convenience of being able to walk right in from the house. One big thing that gets overlooked when designing a greenhouse for the North is cooling! I work in a commercial greenhouse with roll-up curtain walls and if the air is still it can be over 20 degrees warmer inside than outside. We have sections that regularly get over 110F in the summer! When I build my greenhouse it will have ridge vents and ground level wall vents. Cool air will enter at ground level and get heated up. Hot air rises and exits through the roof vents.

When we are back in Ohio, I will have to get you the contact info of a friend of Jeff's family who had a greenhouse added on to her house during a renovation.

Cool! Yeah let me know! Glad you're coming back! :)

We are going to heat ours off the grid (hopefully). We are building a rocket mass heater. It is pretty darn cool. Rocket Mass Heaters