Greenhouse placement

I have absolutely no experience with greenhouses and I am thinking of diving right in. The area that I am finding the most conflicting information is greenhouse placement, i.e. too much light, not enough light, etc. My house sits atop a small hill facing west, and the western sun can be brutal. To the east and south there are trees, but some 30-40 yards from my house. I would like the greenhouse to sit to the south of my house. However, on the south side of my house the ground slopes down to a basement level door near the front of the house. There is a retaining wall that stair-steps down to the ground from about 10 feet high and 30-40 feet long. My ideal situation is to build a greenhouse attached to the door extending out to the south. I thought this could give me 2 light "zones" within the greenhouse. The side closest to the house would only receive about 5-6 hours of sunlight while the furthest side would receive full sunlight that I could shade if need be. The wall stays very warm and I thought this would add additional heat in the winter. My question is would this allow enough light, or is the wall going to be too much of an obstruction to work with?

Welcome Derek! You didn't say what climate zone you are in and how insulating your greenhouse will have to be. Placement is usually decided for you by where your house is located, if you are going to build off the house like I did. The front of my house faces southeast, and along the southwest wall, I framed a 8'x20' greenhouse with 2"x3"s and used 6 mil clear polyethylene sheeting for the insulation. Here in zone 8 (with climate change becoming zone 9) I don't need much insulation, just to keep the ground heat from radiating up on clear nights. Our soil temperature rarely drops below 50F, so a few hours in the 20s is not a hard problem to deal with.

The way you describe it, you could use the retaining wall as a key feature of your design, maybe even paint it black so it can radiate heat back into the greenhouse at night. My greenhouse is seasonal, it goes up in November and comes down in late March. If that is your plan as well, you may want to think about what kind of panels you can assemble off the retaining wall to give you the area you need to keep plants over the winter.

I am in zone 7a. As far as material I will probably use a thick plastic sheeting and maybe once I figure out if it is a good location, switching to a polycarbonate. I want use sort of a "convertible" approach so during the summer if the heat is too much, I can open it up. I just wanted to get a more experienced opinion on that west wall and if that would keep it from being a decent location.

You could leave the walls in place all year and by "open it up" remove a good size section of the top so everything doesn't bake in the summer sun. It will take a little trial and error and monitoring of temperature until you get a feel for it.

One thing I can really recommend is using stud lumber to frame it. That way you can have 2 layers of insulation. At first I only had sheeting on the outside of the studs, but when I added it to the inside of the studs as well, it worked out much better.

I have to agree with John about stud framing and Double plastic. My green house has a solid west wall that I painted white to increase light. I have table grapes growing on the out side of the east facing side. This shades the greenhouse in the summer, and lets the light in in the winter. I recently put in a rain gutter wicking system in the green house, and am finding the plants do much better.

I am new here and don't have much idea how things work here but I would say taking a professional help might sort out your problem. I can suggest envirotechgreenhouse.com as a solution. You can contact these people any time and they are always ready to help.