Chapter 2: Types of Greenhouses
After you decide that you want to build a greenhouse, you have to decide next what type to build. This should not be a difficult one to address, provided you know what kinds of plants you want to grow.
You will need
to answer questions such as:
> What will my greenhouse be principally used
>Do I want a large or small greenhouse?
>Will the greenhouse be the main attraction of
>Is my garden exposed to strong winds?
>Are there young children or wild animals in
Factors such as cost and space will determine the type of greenhouse you build. If you do live in a windy area, it may be worth to spend the extra money for a solid and sturdy greenhouse. If you live near a large hardware store or a nursery, or even a do-it-yourself home center, go and visit some models. The customer service representative should be able to provide you with valuable information before you make a final decision.
So as not to mislead you, while there may be different types of greenhouse designs, we’re talking about the same greenhouse. You get to decide which type you want it to be. For example, if temperature is the main factor, because of the plant varieties you want to grow, then there are three types in terms of temperature control. There are also different types of greenhouses based on structural design. We’ll start with temperature control factors.
For temperature control purposes, three types of greenhouses exist:
>a hot greenhouse
>a warm greenhouse
>a cool greenhouse.
A hot greenhouse’s inside temperature is maintained at a minimum of sixty five degrees. You can at some future date increase the temperature, but a hot greenhouse is intended for growing tropical and exotic plants. If you live in a very cold region, you will need to install heating and lighting equipment to satisfy the requirements of tropical and exotic plant species.
The temperature inside a warm greenhouse, on the other hand, is at about fifty-five degrees F. At this temperature, a larger variety of plants can be grown, perhaps as many as you would in your outdoor garden. You may still need to resort to the use of additional heat and light during the winter months.
A cool greenhouse (frost-free greenhouse) is maintained at a temperature ranging from forty to forty five degrees F. This temperature is ideal for growing seedlings or any plants that do not need warmer temperatures to survive. A cool greenhouse is perfect for starting your plants and vegetables in anticipation of the summer months. Generally, the use of heat or lights isn’t required for a cool greenhouse.
As for structure, there are generally three types:
> ridge and furrow or gutter connected.
The lean-to type of greenhouse is rarely used for commercial purposes because of size restrictions, but is
the most popular among hobbyists.
Detached greenhouses – as the name suggests – are independent and are stand alone structures. However,
they may still be attached to a work area or else provide access to another greenhouse via a passageway.
The Quonset is the most common type of detached greenhouse used for commercial production. They are built from arched rafters and have solid walls for support. Quonset greenhouses are ideal for producing most crops, although the growing area is limited to the areas around the side walls, which diminishes efficiency and productivity.
Ridge and furrow greenhouses are attached at the lower edges of the roof by a gutter. The absence of an inside wall below the gutter allows for increased efficiency. Ridge and furrow greenhouses may be built with gabled or curved arches. Gabled houses are appropriate for heavy coverings (i.e. glass, fiberglass) while curved arch houses are covered with lighter materials (i.e. polyethylene, polycarbonates).
You may encounter different classifications in your readings on greenhouses. For example, another classification, which is similar to the ones just mentioned are:
Cold frame type
Roof cover may be poly or shade, end wall covering is either poly or rigid, available lengths come in 12 feet increments, and no gutter connections or vents.
Roof covering is either poly or shade, wall covering may be poly or rigid, lengths available in 12 feet increments,
no gutters, roof vents are available.
Gutter-connected, Gothic arch
Load rating may be either 10, 15 or 20 pounds, roof covering is poly, sidewall and endwall either poly or rigid, lengths available in 12 feet increments while heights available in 8, 10 or 12 feet, gutter connection and roof vents both available.
Load rating 10, 20 or 30 pounds, roof covering either
poly or rigid, endwall and sidewall covering may be
either poly or rigid, lengths in 12 feet increments,
gutter connection and roof vents available.
Load rating may be 10, 20 or 30 pounds, roof covering and sidewall/endwall is rigid, lengths come in 12 feet increments, gutter connection and roof vents available. Another way of looking at greenhouse types is the
material they are made of; that is, glass, fiberglass, or plastic. Each type has its advantages and disadvantages. Whatever you choose, make sure you leave the installation and irrigation systems to professionals.
Glass type greenhouses are the most traditional covering used. They may be constructed with slanted sides, straight sides and eaves. Aluminum, glass buildings provide low maintenance and have aesthetic lines, as well as ensuring that you get a weather-tight structure. Pre-fabricated glass kits are available for easy installation by hobbyists and amateur gardeners. They come in different models to meet budget and space restrictions. The disadvantages of glass are its fragile condition (glass breaks easily) and high costs.
Fiberglass greenhouses – they are light, strong and hail-proof. Be careful, though. Low quality fiberglass will discolor, thus reducing penetration of light. Using a good quality fiberglass will however make it as expensive as building a glass one. If you decide to go for fiberglass, go for the most expensive grade, and do not buy colored fiberglass.
Plastic greenhouses are becoming very popular for the
> Low cost (about 1/6 the cost of glass)
> Absorbs sufficient heat
> Fruits and vegetables and other plants under
plastic are comparable in quality to that of
> Lower tax liabilities
Choice of polyethylene (PE), polyvinyl chloride (PVC), co-polymers of these materials, and other readily
available clear films.
Polyethylene: lightweight and inexpensive. It stands up well during the seasons of fall, winter and spring, but tends to deteriorate during the summer when it gets constant exposure to the sun. It breaks down due to ultraviolet rays and the deterioration begins along the rafters and along the creases. This problem can be avoided by using UV-inhibited polyethylene, which is available in two and six ml thickness and is up to 40 feet wide and 100 feet long.
Polyvinyl chloride (PVC or Vinyl) – like polyethylene, PVCs are soft and flexible. You can have transparent ones. Vinyl costs two to five times more than polyethylene. When properly installed, they can last as long as five years. Because it attracts dust and dirt from the air, it has to be washed from time to time.