The standard definition of a greenhouse is a glass (or clear-plastic) enclosed structure used for growing plants in a controlled environment. That being said, greenhouses are not the same – they come in different shapes, designs and styles. They differ in purpose too - some are meant for use during specific seasons (e.g. a summer greenhouse) while there are those that work fine irrespective of time of year. Often, the suitability of a greenhouse for year-round use will depend on its shape. The shape determines headroom and airflow which are key factors in the greenhouse’ efficiency as far as temperature control is concerned.

Classification by shape

• The Traditional Rigid Frame greenhouse has vertical walls. The Rigid Frame has spacious headroom and efficient air circulation. There are no support columns so the rafters are solely supported by the structure’s walls. Due to the absence of pillars to support the roof, the weight from the rafters as well as the walls themselves is concentrated at the base of the walls around. The foundation must therefore be deep and strong to ensure it does not crack or buckle over time. It is this strong foundation that makes the Rigid Frame among the better options for an all-seasons greenhouse.

• Post-and-Rafter and the A-Frame – The shape is simple and structure holds up well especially in locations where strong winds are common. Like the Rigid Frame greenhouse, the Post-and-Rafter and the A-Frame are spacious and have good air circulation. They work well when deployed for all-season use though their main drawback is the quantity of construction material required to build them.

• Quonset Hut – The Quonset Hut shape is probably the most distinct of the three shapes. It uses bent metal tubes for the frame and has a circular shape. This makes plastic sheets most suitable for its walls and roof since it would be expensive to fit glass walls along its round frame. The downside to the Quonset Hut is the smaller headroom and strained air circulation. Quonset Huts are therefore best suited for a seasonal greenhouse.

Classification by support style

• Unsupported – Unsupported greenhouses are free standing and not supported by any other building or structure. The vast majority of greenhouses fall under this category.

• Lean To – ‘Half’ a greenhouse is mounted against the external wall of a building or other structure. There is often no doorway from the supporting building leading directly into the greenhouse – instead, entry is from the outside.

• Even Span – One end of the greenhouse is mounted on a building or other structure. Most Even Span greenhouses use the Quonset Hut shape as it is the easiest to mount on this support. However, some greenhouses use the Rigid Frame, Post-And-Rafter or A-Frame.

With this understanding of the different greenhouses and the circumstances under which each would be most suitable, you should find it a tad bit easier to determine which shape and style is ideal for your requirements. Take time before making your decision since the cost of pulling down then erecting a new greenhouse can be huge.