DIY Solar Greenhouse

Location and Orientation

• You probably have a spot picked out for your greenhouse that gets plenty of sun each day. Take note of where shade falls where you plan to build. Dappled shade from a tree is less of a problem than the solid shade of a tall building.
  Now, how to orient the structure? Basically, face the equator. In the northern hemisphere, this means build so that your greenhouse faces south, and will soak up sun all day as the sun travels across the sky.

Materials

• A greenhouse can be built of anything from plastic sheeting to custom glass windows. Your budget and available time will determine what you choose.
  For a quick and inexpensive greenhouse, make hoops of PVC pipe, and cover them with clear plastic sheeting. Put a door in the end, or hang sheeting down that you can lift out of the way. Put your plants right in the ground inside the hoops, or start in flats up on tables or benches.
  Recycle windows from a remodeling project. You can build a 2x4 structure around the windows you have available.
  Use corrugated fiberglass. This translucent material is lighter and less fragile than glass, and more durable than plastic sheeting. It does degrade over time, though.
  Whatever materials you choose, plan to start with a foundation, even if it's just a frame of 2x6's laid on the ground. Also, consider whether insulation will be necessary in your climate.

Heating and Ventilation

• You want it to be warm and cozy in your greenhouse, but too much heat will kill your plants. Provide vents in your structure that can be opened to release excess heat, and closed to retain heat overnight. These can be complex, automatically opening vents with fans, or just windows you can prop open. If you're using plastic sheeting, you can roll up the sides and secure with clips. Unroll them at night.
  Depending on your climate, you also may need to provide a source of heat. In northern areas, a simple portable electric heater will allow you to start seeds and care for frost tender plants through more months of the year. If you're determined to use your green house through a northern winter, you will also need lights to supplement the short hours of daylight.