At the time of this writing, it is the middle of spring and I have just finished cleaning out my greenhouse so I can start growing plants in it. Along the way, I decided to take a few pictures and give some information on it. Perhaps this page will inspire someone to go out and build their own.
Recycled Materials
This greenhouse was constructed almost entirely from recycled materials, so it didn’t cost me anything to build. The glass actually came from a Ramada Inn. At my house, there are over a hundred pieces of it laying in a pile. Someone who worked for a construction company gave it to my family in a “take all of it or none of it” deal. This glass was only a tiny fraction of the stuff the guy had collected over the years, so he was ready to start getting rid of it.
The foam insulation was part of a similar deal. Normally, I do not like to use foam because it’s not very eco-friendly, but, if I didn’t use it, the foam would have just ended up being thrown out.
Is It a Solar Greenhouse?
Because of its design, I say that this greenhouse technically qualifies as a solar greenhouse; however, it doesn’t have any thermal mass to help keep it warm during winter nights. At one point, I did have barrels of water set inside to serve this purpose, but I decided that they were using up too much of the limited space and took them out.
Even without the thermal mass though, I would still say that it qualifies as a solar greenhouse because it heats the attached building quite nicely even while it is very cold outside.
Everything I learned about building solar greenhouses came from The Solar Greenhouse Book. It’s an older book, so you can get it really cheap off of Amazon. At the time of this writing, it cost about 25 cents for a used one. 
Size
At about 8′x8′, it’s not a very big greenhouse, but it does what I want it to do, which is extend the growing season.
The Inside
Here’s a picture of the inside of the greenhouse. I removed one side of the foam insulation so that I could get inside to clean easier, which also had the side benefit of making it easier to photograph.
The plants I grow are done hydroponically. I’m kind of a tech freak, so I like to do things that are somewhat futuristic. Once the system is set up, I don’t have to do anything besides make sure the water stays topped off and replace the nutrients every couple of weeks. I eventually want to make it so that I can leave it untouched for an entire year, but that’s a project for another time. : )
You can see part of the hydroponic system in the picture above. I still have a couple more tubs to set up before it’s finished.
I wish I could show you some of the pictures I had from previous years with the plants at their full size, but, sadly, they were lost on a hard drive that went bad. For some reason, they didn’t get backed up. For now, I’m just going to have to wait for these little guys to grow up before I can take new pictures. They may look small, but, before long, it will be a jungle in here.
Insulating the Perimeter
Building this greenhouse was a pretty straight forward process. The one thing that took a lot of work though was insulating the “foundation’s” perimeter because I had to dig a two foot deep trench all the way around. In the picture below, you can see the insulation sticking out above the ground. It’s pretty thick, so I had to remove quite a bit of dirt.
Glazing
I didn’t put much thought into the angle of the glazing. I just picked one that was convenient. Oftentimes, it is installed so that the glazing will be perpendicular to the rays of the sun when it is at its lowest point in the winter. Doing this helps maximize solar gain when it is needed the most. This isn’t written in stone though. It really depends on what you want to do with your greenhouse. For example, if you only want to extend the growing season a few months, you might choose an angle that is optimum for the fall and spring periods.
I used caulk to seal the glass so that water and cold air wouldn’t leak in. if I were to do it again, I might try something like weather stripping instead. There are two reasons why. The first is that it took a lot of work sealing all of the cracks and the second is that, now that it’s finished, I can’t easily take it apart because the caulk has “glued” everything together.
Being able to take it apart would be convenient because there is water vapor trapped between the two layers of glass which I would like to let evaporate.
Cooling
Keeping a greenhouse cool in the summer can be a tricky thing, especially with the smaller ones. When I first built mine, all of my focus was centered on keeping it warm in the winter, so I didn’t plan enough for cooling. This led me to have to retrofit it later on.
To help keep the greenhouse from overheating, I first added a shade cloth and then put a vent in the roof which opens to let hot air out. You can’t see it in the picture, but there is another vent across the back of the greenhouse near the floor. This one has fans installed in it to blow the cooler air underneath of the attached building into the greenhouse. I’ve grown plants through the hottest summer days without trouble.
