Now that I am unemployed, I thought I would start a major project to help get rid of any excess funds I had. The plan is to build a ‘solar greenhouse.’ I know this sounds redundant, but the idea is that the greenhouse will be heated entirely through passive solar heat. So, the first step was to get an idea of where the sun marches across my skies. There are many ways to do this, the oldest and best probably being observation. But I cheated. I looked it up on the internet using the University of Oregon’s Solar Radiation Monitoring Laboratory’s Sun Chart Program.
Based on this chart, the sun will reach an elevation of 50° on March 20/21, the vernal equinox. The sun then continues to climb higher and higher in the sky until May 21, when it reaches 70° and June 21 when it reaches about 73°. I also noted that on December 21, the sun’s elevation only gets to 26°. My thought was to make all these numbers work in my favor. I definitely want/need full sun between September 21 and March 20, so I made sure the front wall does not block sun on December 21 and I made sure the roof does not block any sun on March 20. My Northern roof line is going to be 50° then, to insure that the sun can hit the back wall on March 20, and my front wall will be 48″, to ensure that the December sun is able to hit the back wall as well. The next challenge is to determine how far out to make the solid Northern roof go in order to block the Summer sun from hitting the back wall of the greenhouse, in order to keep temperatures from soaring out of control in the Summer. For this, I drew a line at 70° from the base of the back wall and found where it intersected the roof line. That intersection is where I will place the peak of the roof, which is approximately 15′ above the ground level. For people more accustomed to roofing terms, this means my Northern roof will slope at 14/12 (50°) and my Southern roof will slope at 24/12 (65°).
Some additional design considerations included the size of the area set aside for the greenhouse. Initially, I had set aside an area of 16’x16′ for the greenhouse. After drawing the plans repeatedly, I decided to alter the size to 12’x16′, leaving room for a cold frame along the Southern wall of the greenhouse. Also, the Northern wall will be framed with 2x6s in order to allow more insulation to keep out the cold Northern wind. Likewise, the Northern roof will be framed with 2x6s. I plan to put a large water tank in the greenhouse as well as stones/bricks/cement blocks in order to store the solar heat as it comes in during the day. These same items will then release their heat overnight to alleviate extreme temperature fluctuations.
My plan for the flooring is the most exciting yet. For the floor, I will lay down 2″-thick polystyrene insulation panels in order to insulate the cold ground from the floor of the greenhouse. I will then pour 1″ of sand over the insulation. Finally, I will install 2″ brick pavers over the sand. The brick pavers will allow the solar heat to be stored in the floor while also providing a pleasing floor for users of the greenhouse.
The least exciting part is the foundation. I will be going 3′ deep in order to avoid frost heave that would potentially ruin my new struction. This will be accomplished by pouring a footer that reaches 3′ down, then stacking cement blocks on the footer until I get above ground level. I calculate I will need 2 cubic yards of concrete for the footers and 160 cement blocks for the foundation walls. The disappointing part of all this is that all that work will be covered up by dirt and (hopefully) never seen by anyone. That is alot of work to do for noone to see.
So far, I have been digging out the HUGE hole that is necessary for the footer and the space I will need to work on the cement block wall. I have been helped immensely by my father-in-law, Dale, who has been driving down to help out on our rare days when it is dry enough to dig.
I know this is an entirely unsatisfying picture, but it isn’t wholy irrelevant. You can see the large dirt space on the left side of the picture, which is where the greenhouse is being built. Also, the two people in the picture are my daughter and my father-in-law Dale.
Garden from West, May 2009