Hey there!

As the title states, my wife wants to build a large greenhouse (roughly 10-12' wide, 30-32' long).

She's a longtime gardener but has never done a greenhouse before. I'm clueless on all fronts but very handy and follow instructions well

We live in the Midwest, a zone 6 hardiness zone. She wants to be able to keep the greenhouse heated through the winter. Propane will likely be our most realistic heating option.

Can I get some suggestions for where to start looking for manufacturers? So far I've done a little reading about Grandio greenhouses. Are there other kit manufacturers I should consider? Is there any reason to avoid them?

What else should I know before starting? I'm not even really sure what questions to ask.

Thanks for any help you can offer!

First, I have to say I'm jealous.

Regardless of the size of the structure and manufacturer that you settle on, you will need to check on the following before purchasing your structure.

Check your local zoning restrictions to see if they allow that large of a structure with out special permits.

Heating
You say that propane would be your most viable heating source. Check with local bulk suppliers regarding tank size, cost and permitting. There may be restrictions on how large a tank you can have and the cost of piping and heaters. Also check on propane pricing and delivery schedules.

Cooling
You will need some kind of cooling system for the warmer/hotter parts of the year. Even if the greenhouse has roof or sidewall panels that open for ventilation, you will most likely need fans for circulation.

Irrigation
Another cost to check on is a water supply. Will you use well water? If so, do you need to have a new well drilled. If you're planning on connecting to the municipal supply, what are their connection and monthly costs.

Once you have your start-up and recurring costs in hand, you may be able to convince her to start smaller. If all works well, you can always add on.

Best of luck! And again, I'm jealous.

Hmmm, I am seeing 'the top 10 greenhouses of 2024'. Midwest, are winds constant or high? How much sun do you average? How will you cool it in summer? and what Rick said.

@MoonShadows

Welcome @dangles

First, if you haven't done so already, I would recommend you and your wife read every greenhouse thread in this forum for the past few years. There are a lot of opinions, good ideas, and good advice already here in this forum.

How experienced a gardener and what does she know about greenhouse growing? Before you drop a load of cash on something big and expensive, some people buy a smaller, cheaper one first to see if they will like greenhouse growing, and if they do, they upgrade after a while. My first greenhouse was a less expensive 8x14 greenhouse back in 2016 (@$4000). Last year I put up a 14 x 20 that is "top-shelf" ($23,000+ for greenhouse and extras), more than doubling my greenhouse square footage.

I have sold greenhouses online and have had two greenhouses myself. Be careful! They will advertise a greenhouse to make it sound like the best thing since sliced bread to get you to buy it, but it may not be the best for your plants, zone, wallet, long term heating/cooling costs, etc. They will even tell you it's a 4-season greenhouse when it actually isn't and would be like trying to heat your open front porch during the cold months!

At this juncture, unless you are going to build from scratch like some very talented folks have done here, I can only recommend 3 store-bought 3. They are not cheap and only for the serious and experienced, or new and EXTREMELY motivated, greenhouse growers, but they are the best out there IMHO. Growing in a greenhouse is VERY different from growing outdoors, and there is a real learning curve to be good at it.

RIGA
I currently own a RigaXL6 -14 x 20. They are available in up to 14 x 30. Has just about the highest snow load and wind rating of any greenhouse sold in the US and one of the few that was actually tested under snow/wind conditions. Aluminum Framing with two strong doors and 4 roof window vents. The polycarbonate is 16mm, triple wall, just about the best you can get. It is imported from Germany by Exaco, but only sold through distributors (shop around!). You will need at LEAST 2 people to assemble, 3 or 4 is even BETTER. I built it with one other person, and it was difficult since everything gets locked in, and it is one solid unit.

I installed an automatic 20" exhaust fan in mine with an 24" automatic intake louvre. On hot days, I can vent the entire air capacity in the greenhouse in less than a minute if it gets too hot. I put in a 425-gallon pond for a heat sink in the winter, and a cool sink in the summer. I also installed Phase Change Material Panels on the north wall as a heat sink in the winter and a cool sink in the summer. I grow all year. https://exaco.com/greenhouse-r...

CERES
Very customized, very expensive. Might be as strong as a house. Probably the best insulated of all three here. https://ceresgs.com/

Growing Spaces
My favorite greenhouse because of the character, versatility, and ability to grow all year. With that said, I did not buy this greenhouse because the size I wanted was out of my budget and it would not fit where I wanted to place the new greenhouse. https://shop.growingspaces.com...

Read the threads and take a look at these greenhouses. If you have questions, let us know, and keep us up to date on your progress. Once again, welcome.

Jim

Great information above!

I would say the first question is "what will be grown in the greenhouse?" In addition to heating, you may need to supplement the lighting during the winter months (depending on the answer to what will be growing). Anything that needs to make flowers - such as tomatoes and peppers, or flowering ornamentals, will need extra light in the winter months. And in the summer you will definitely need good ventilation and cooling (as above) and quite possibly will need to use shade cloth as well. Best of luck with your project!