Your greenhouse's height will influence the amount of heat your structure retains, the amount and type of ventilation it will require, and the kinds of crops you plan on growing. Greenhouses roof heights and overall styles run the gamut from Quonset hut structures, to A-frames to lean-to's. These structural differences are more than just aesthetic concerns. Form and function are dependant on one another.
Sidewall heights effect the type of roof your greenhouse supports. Quonset huts, where the sidewall arcs into the roof, result in limited space and headroom. A-frames' feature peaked roofs, which allow greater air circulation and more headroom. Lean-to's are smaller than other greenhouses, but because they are often attached to a home, they are easier to heat. Unlike stand-alone greenhouses, which have even span roofs, lean-to roofs are uneven. One side of the roof receives more light and heat than another. Structures such as this require additional ventilation in order to evenly distribute heated air.
Roof Pitch And Height
Standard greenhouses have a 6/12 roof pitch which is equivalent to a 27-degree angle from the ground's surface. To achieve this angle, a greenhouse must have appropriate sidewall height and length. University of Georgia horticulturists state that "the difference in height between the centre of the greenhouse and eave will be one-half of 9 feet or 4.5 feet with a 6 in 12 roof slope. If the eave is 5 feet high, the greenhouse should be 9.5 feet high at the centre." Following these dimensions will help a grower provide their crop with optimum light reception and air circulation.
Greenhouse growers strive to maintain a uniformly heated growing environment for their crop. During harsh winters, they need to know how to heat their greenhouse so their tender seedlings do not die. Growers use mathematical formulas to determine the amount of heat they need to provide to ensure optimum temperatures are maintained. Heat is measured in British thermal units (Btu) per hour. To determine the number of Btu's needed per hour a grower must know the area of their greenhouse. Area is the sum of the square feet of surface area taken up by the sidewalls, roof and gables. The greater the area the more heat is required. The higher your roof, the greater the area and the higher your heating costs.
Depending on your climate a high roof can be an attribute for growers. In cold climates high roofs mean higher heating costs, but in hot climates, high roofs aid in ventilation. Cool air circulating through a hot, humid greenhouse will prevent crops from succombing to powdering mildew, root rot and fungal diseases.