Earth-Sheltered Solar Greenhouse, Year Around Food out of Recycled Materials

Everyone knows that a greenhouse is essential for having produce during the winter. But the heating costs for a glass building can be horrendous.

I would like to expose everyone here to the idea of The Earth-Sheltered Solar Greenhouse and a novel way to build one using recycled materials.

Your normal, above ground, greenhouse loses heat on 5 sides and only retains heat on one, the ground. An earth-sheltered greenhouse has 5 insulated sides and only 1 to lose heat through. Also, the earth exposed to the suns rays absorbs the heat which it will radiate all night. Along with the temperature of the ground staying above freezing all year round. (the temperature of the earth, about 5ft+ down, is the about the average air temperature of the year.

Also this earth-sheltered greenhouse is a great place to grow animals like rabbits. The rabbits provide heat and CO2 for the plants. (and fertilizer) It also protects the animals from freezing temperatures and winds. With the correct animals, the greenhouse becomes a much better, more robust system.

An earth-sheltered greenhouse is very effective in colder climates allowing growing year round without having to have a furnace to keep your plants from being frozen. It provides warmer winters and cooler summers due to the earth storing heat all year round. I feel it is one of the best ideas Mike Oehler has come up with, and he has come up with quite a few.

Mike Oehler has written THE BOOK on underground housing. His ideas are revolutionary and solved many of the problems that come with building underground. He has built several underground homes and continues to live in them. And these are not dark, damp cave like dwellings. They are warm, comfortable and naturally lit.

You can get Mike Oehler's awesome books at his website:
The $50 and Up, Underground House Book.
http://undergroundhousing.com/
The Earth-Sheltered Solar Greenhouse Book
http://undergroundhousing.com/greenhouse_book.html

My addition to this idea is making the earth-shelterd greenhouse out of used tires and packed earth. Building a circular, sloped retaining wall out of used tires is a very strong and long lasting structure. It also provides a large black surface to absorb the sun's rays. Another use for used tires; a recycling nightmare.

There are many sloped, earth filled retaining wall systems. Basically what you need is something to keep the earth from falling down, and the earth itself will easily hold a 3:1 slope. (check with your local engineer) You can see stacking concrete block, earth filled retaining wall systems at all the big hardware stores, and get an idea of what slopes can be achieved.

To start, you dig a big hole, or build up a mound. This will depend mostly on drainage. You will want the floor of the earth-sheltered green house to drain, else you will have problems with the structure filling up with water.

After you have laid your drainage pipes, you start placing the first ring of tires in a circle that will be the size of your greenhouse. Then you fill the tires with dirt. (not garden soil. Sand with a bit of clay is good, some small rocks too.) You pack the dirt into the tires using a sledgehammer or other compaction tools. Then you pack dirt outside the tires and pack it firmly. When the dirt is level with the tops of the tires all around, you put another circle of tires on top. A little larger then the circle below, and begin packing again.

Continue stacking and packing tires until your greenhouse is the height you want.

After all the tires and packing are done, then comes the roof. You will want to pour a concrete, steel reinforced, ring around the top row of tires. This will support the roof joists and keep them from spreading, which would cause the roof to collapse inward. There are several ways to build a circular roof. One is to put a beam across the middle. Then a little upright. And you place all of your rafters radially out from the center.

Other considerations in designing this greenhouse is to slope the south facing wall so that the winter sun is not blocked. You can make the rings of tires wider on the south to decrease the slope. This makes the structure more stable, but will require a bigger roof when you finally get to the top.

And lastly, you will want to design where you are going to put the ladder or stairs to get down into your greenhouse. Or if you build this up as a mound, you can design a door into the wall. Usually using a concrete post and lintel. Or similarly out of railroad ties. (see articles on building houses with tires for how-to)