Chest freezer with an aftermarket temperature controller. Commonly called a “keezer” in the homebrewing community.

My dream is to one day have a setup like this. Like others said, humidity and heat in a greenhouse are 2 big concerns. They make all kinds of automated systems for opening vents, etc.

If your primary goal is growing in a contained area to keep pests away (vs. needing to really keep the space warm in winter or something), you best bet could be a hoop house. Basically you can drive rebar or fence posts into the ground, and then arch something (pvc pipes commonly) from one side of the space to the other. You’d then pull plastic sheathing overtop. Those are commonly used to get growing started in early spring and extend growing in the fall. When it’s warm enough, they basically roll up the material. You could do something similar but still have a structure of chicken wire or netting or something to keep animals away.

If you actually want to keep the space warm to grow in the winter, you might want more permanent walls with better insulation, like double walled polycarbonate.

Another thing to consider is water. If you have a greenhouse next to your house, you don’t want rain that falls on it to direct water to your house’s foundation.

Searching around, it seems like stucco and high humidity may not work well together. Personally, I’d be a little concerned about algae/moss growth on my walls if I had high humidity on stucco.

I love the look of repurposed windows/doors for greenhouses, and I’ve even seen them advertised for that purpose at resale shops, but it’s really important to be careful about lead paint if you want to do that. Lead was the primary white pigment for a long time, and since windows/doors are often trimmed white, if they are older than 1978 (in the US, EU was 2003, though many member states had their own laws previously), it could be lead. Lead testers are fairly cheap if you want to go this route.

The right side is where people farm and the left is more ranching. Obviously, there’s farms everywhere, but out west, it has to be irrigated, which can only be done cost effectively in certain locations.

If you know where to look, you can even make out rivers. The Platte river crosses the great plains to Denver (the big blue area).

In case you aren’t American, that line is the Great Plains. It’s basically the dividing line between where it historically gets enough rain to farm, and where it’s dry enough that farming gives way to ranching.