[permaculture] Dryland greenhouse
Paul A Cross
charybda at newmex.com
Wed Feb 20 16:13:56 EST 2002
Thanks John for your posting. For some reason, my message from Jan 25 hit the list within the last few days. We've been making some progress on the greenhouse, and that progress has changed everything once again.
I sat down and did the calculations based on 100-year monthly precipitation records. This led me to determine that I only needed 10K gallons of storage to make it through the transplant season. Next thing that changed the project was hitting bedrock with the backhoe. We simply couldn't put the water underground without major blasting. The third change was running over budget on contruction, so the larger tank will have to be a retrofit.
Now I am thinking more about a smaller tank indoors above ground installed right away to have some warmer water and as a backup in case of pump failure, followed in the future by a larger tank outside, either bermed in or insulated with straw bales or rastra.
Water is too cold for greenhouse irrigation at 43F, and ideally we'd irrigate with water between 65F and 80F so we're not bringing the soil temp down around the plants. Since the input water will often be snowmelt, that water will be around 33F. We will want to warm it up if we can, and figure on a small black tank or two in the sun to do this.
The foundation for the building is pier footings. We will insultate with R10 for 18 inches below grade. The plumber suggest putting the water pipes 5 feet below ground to avoid any freezing. We'd insulate down further than 18" for the perimeter but for the rock we've already hit. Some insulation is better than none, I figure. Inside the greenhouse is simply dirt covered in weed cloth, with raised platforms for container growing.
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