So we decided to use what we had to modify and that gave us this almost finished straw bale greenhouse that you see to the left.
Process: We started with our existing shed and its south facing exposure and added three raised beds using recycled pig penning or PVC with some recycle wood. We then built the frame using the raised beds and shed structures to support clear plastic roofing made to let the sun in. We considered framing it in all the way, however decide we could remove the straw next year and use it to grow potatoes while letting our green house breath for the summer. We haven't yet and it isn't shown but we will be adding plastic sheeting on the inside and outside of the straw bales to keep moisture out. Since the shed is directly outside our east end door of the house we have easy access to water, however we plan to eventually add a rain barrel to collect water. Finally, we plan to add shelves on the wall of the shed to use in seedling/starter seeds in the spring.
This project cost just the price of the roofing - clear corrugated roofing panels was approximately $300, the remaining materials were free to us, including the straw. The size of the greenhouse is 10 feet by 14 feet.