Cost to Build

• The Passive Solar Greenhouse is a free-standing insulated building on an insulated foundation, that-if built according to the specifications in the blueprint-will last at least 30 years with minimal regular maintenance. 
  


• The whole building is 515.5 square feet; the interior is 350 square feet. Another 80.5 square feet is the foundation and pad for the cistern. 
  


• The cost to build the passive solar greenhouse cannot be stated exactly because it is not a kit that can be shipped to your home. 
  


• Building materials are more expensive in some parts of the country than others, and many factors affect cost including time of year, whether the materials are new or salvaged, access to urban or wholesale markets, and choices about grades and kinds of wood. 
  


• Labor costs will also differ based upon both the skills of the owner/builder and the hourly rates for skilled and semi-skilled workers.

Materials

The Passive Solar Greenhouse is comprised of the following specifications:

• Foundation: concrete footer with a 2.5 foot insulated foundation, two feet of which is below grade (underground). 
  


• North wall: six feet concrete slab, strawbale wall, post and beam frame and stuccoed inside and outside with two coats of cement stucco; R value over 40. 
  


• Side walls: conventionally framed with both fiberglass and radiant barrier insulation to equal approximately R23, with a sealed three-quarter inch COX plywood exterior and stucco interior. 
  


• Glazing wall: redwood 4"x4" x, 2"x4" inch purlins, R23 insulated knee wall, and 4x10' panels of twinwall polycarbonate in an aluminum frame. 
  


• Roof: conventionally framed with 2"x8" rafters, both fiberglass and radiant barrier insulation to equal approximately R33, fully decked roof with five-eights" wafer board 15lb. pound paper and 30 year metal roofing, plus two gutters. 
  


• Two screen doors, two solid wood doors, two large manually operated vents, one solar powered vent, one solar powered 16 inch fan, three small solar fans, one 10-watt (12 volt) solar panel and two solar panels providing 42 watts at 24 volts. 
  


• 90 metal and 90 plastic five gallon buckets to hold 900 gallon water wall. 
  


• An insulated 1,225 gallon black FDA approved plastic cistern with fully insulated spigot, all sitting on its own cinder block and treated wood foundation/pad. 
  


• Total materials cost is approximately $8,150 US or $7,000 without the solar fans and panels, cistern, spigot and the cistern foundation/pad.

Labor

• When I began this project I was basically unskilled. The building process taught me how to read a blueprint, how to do basic carpentry, and how to be an owner/builder, where you are the general contractor. 
  


• In calculating the labor costs, I am assuming one owner/builder, one journeyman grade carpenter, one part-time skilled helper, and one part-time semi-skilled helper. 
  


• The total approximate labor cost is $6,150 US or $5,600 without the solar and cistern installation. 
  


• This whole project was a bit of a neighborhood sensation! I received many hours of help from friends and neighbors, especially in the pouring of the foundation. Other people traded their labor, with the end result being that I actually spent only about half the labor cost in cash. I also became well-acquainted with several teenagers in the area who were often my helpers, learning along with me. 
  


• These labor figures do not include the time or cost of preparing the beds, planting the seeds, or doing all the research. Much of those costs were met by a small USDA SARE (Sustainable Agriculture Research and Education) grant. 
  


• Another greenhouse of this design has been completed; it has an adobe instead of straw bale wall. Another person plans to use Rastra ™ Block. The design is flexible enough for your creative changes.
  

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