With the ever increasing interest in all things solar due to rising energy costs, greenhouses are no exception. Lots of people have lots of questions about them. There are many differences in the construction of a conventional greenhouse versus solar greenhouse. On the other hand, there are some practices which may be used in either type of greenhouse to cut down on energy bills.
· Location – This is one of the biggest differences. A conventional greenhouse should be facing with the ridge running north to south. This is to obtain the maximum of the morning and evening sun. A solar greenhouse should be placed with the ridge running east to west. This is so you can make the most of the southern facing roof.
· Roof – The roofs on freestanding conventional greenhouses are typically a gable style roof. For a solar greenhouse the southern roof will be at a much larger slant. This is dependent on the part of the country you live in.
· Heat – A conventional greenhouse is typically heated with an electric, natural gas or propane heater. A solar greenhouse will try to collect the suns heat and store it. A couple of these methods are to place metal barrels filled with water under your benches or use rocks or concrete to collect the heat. Also, you can put a heavy curtain on the glazed walls at night. Either of these methods could be used in both structures.
· Walls – The walls on a conventional greenhouse are typically all glazed (covered) with the same material; polycarbonate, glass, polyfilm, etc. The walls on solar greenhouses will be of three types. They will be glazed, insulated or painted to radiate the heat and sunlight. Typically the north wall is painted and the rest of the structure is either glazed or has heavy insulation.
· Ventilation – With conventional greenhouses you will either use passive or active ventilation systems. The passive manner would be using roof vents and side vents. These are often powered with solar roof vent openings. These are basically wax cylinders that work on expansion and contracting. Also, most conventional greenhouses will have curtain walls (swamp coolers) or electric exhaust fans and motorized take shutters. Solar greenhouses make use of passive ventilation and also may be outfitted with a chimney type structure to tie unwanted heat.
If you are really interested in building a solar greenhouse, you should do your homework before ever starting the planning and materials list. There is a lot of information available in books and in papers.