While serving similar purposes, greenhouses and hoop houses are used in different manners. Hoop houses double as inexpensive greenhouses, but greenhouses don't allow the in-ground planting of a hoop house. Heating, structural and equipment differences are important. Consider these differences before choosing the structure that will work best for you.
Shapes & Sizes
Permanent structures, greenhouses can be larger and heavier than hoop houses. Frames are made of heavier wood or steel and sit on solid foundations. Shape is based on personal preference because the constant warmth of a greenhouse melts snow, a major consideration for areas with cold winters. The most popular shapes are even span, uneven span, dome and quonset.
Portability and potential snow load dictate practical sizes and shapes for hoop houses. Lacking snow-melting heat, hoop houses are dome, quonset and Gothic arch shaped. These shapes help snow slide off before the snow causes the hoop house to collapse. Dome shapes are less desirable in snowing areas because snow doesn't slide easily from the top. Hoop houses collapse under too much weight.
Heat or No Heat?
Greenhouses are equipped with fuel-based heaters using firewood, natural gas, propane or No. 2 heating fuel, allowing a constant minimum temperature during cold weather. Plants require warm air above the top of the plant to avoid cold damage. Growing in containers on benches and tables requires heat at a higher level.
Heating a hoop house is left to sunshine and thermal mass only. Growing at ground level only requires less heat. The temperature inside a hoop house will stay a few degrees warmer than outside but is unstable and below freezing in the coldest parts of the country.
Permanent Versus Portable
Greenhouses are permanent structures on solid foundations. Portability plays an important role in hoop houses. Growing plants directly in the ground inside a hoop house eliminates a solid foundation. Portable hoop houses are temporary and sit on baseboards. The steel used in ribs for movable hoop house frames is lighter than in greenhouses. Ribs are clamped to the baseboard and a hip board for stability. Anchoring keeps hoop houses on the ground during high winds.
Moving a hoop house seasonally allows more square footage of ground to be covered over the course of a year than that of a greenhouse of equal size.
Working in a greenhouse is convenient. Benches for plants, tables for work space, running water, electricity and stools to sit on are common equipment. Using space under benches and tables allows for storage of pots, trays, potting soil, coir (coconut fiber), hanging baskets, hoses and watering cans.
Hoop houses allow for little unplanted ground because the best use of space is important between picking one crop and planting the next. Watering requires hoses and drip tape that move with a portable structure. Seed starting takes place in trays, and seedlings are grown to the needed size in small containers. Pots are not used in a hoop house because seedlings are transplanted directly into the soil.
Summer heat is controlled with fans in greenhouses and with polyethylene sides that roll up in hoop houses.