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Introduction - How to build a greenhouse


For the novice, learning how to build a greenhouse can be a daunting task – so is writing about it. This article does not tell you how to actually build a specific type of greenhouse as each type of greenhouse requires different construction materials, building technique, et. However, this article will introduce you to the basics on how to build a green house like planning, budget, location, the types of greenhouses available and some common building materials.

Prerequisites - Things to Consider Before Building a Greenhouse
The type of green house you build will depend heavily on several factors like your start-up budget, the architecture of your home, available space, the amount of space needed, and environmental controls to monitor humidity and control temperature. All these elements should be considered before you delve into building a green house.

Your Greenhouse Budget
It’s difficult to say which of the prerequisites are the most important, however, it’s safe to say that your budget is a primary determining factor in the type and size green house you can build or afford. Tally up your available cash and proceed to the next paragraph.

Available Space for Greenhouse
The amount of space you have is also a primary determining factor in the type and size green house you can build. If you have an unlimited budget and can afford a large, commercial greenhouse, but don’t have the space to house it, then your budget is irrelevant.

Before going into your yard to measure a space for your green house, it’s equally important to choose a good spot. Let’s proceed to the next paragraph to learn about selecting the perfect location for your green house.

Finding the Perfect Location for your Greenhouse
There are many tricks professional gardeners use to maximize the performance of their greenhouse production. Finding the right location is just one of the many things the pros consider when building a green house.

Plant’s will benefit most and are more productive when they bask in morning sunlight. This technique is used to give the plants an early start by allowing the plant’s food production process to begin early leading to vigorous growth and development.

The south or southeast side of your home or shade tress are prime locations. On a seasonal note, the eastside will receive the most sunlight during November to February. However, if you can’t build on the south or southeast side, the next best choice is the southwest and westside where the plants will receive the afternoon-evening sunlight. Locations to the north are the least desirable unless you plan on growing plants that require little sunlight.

During hot summer months, deciduous trees like oak, can "used" as shade for your green house during the intense afternoon heat. Precise planning is required when utilizing techniques such as this because you do not want the trees to block morning sunlight.

During winter months, deciduous trees will shed their leaves and allow sunlight to reach the greenhouse. Avoid building your greenhouse near evergreens because they retain their foliage all year long and may block sunlight during winter months when the sun is less intense.

An ideal location may vary according to your geographical location. Please research your area to maximize morning and/or afternoon sunlight.

Finding the Perfect Location for your Greenhouse - Additional Considerations
It may be a good idea to build your greenhouse above ground to allow rain and irrigation water to drain. The location should also be accessible to sources of irrigation supply, heat, shelter from cold wind and close to a heat source.

For example, if you use computers and electronic devices to monitor the greenhouse temperature, you will need access to a power outlet or source. It’s a good idea to remain close and accessible to all external requirements.

Once you’ve determined where to put your green house to maximize plant growth and the greenhouses’ overall performance, then it’s time to take the measurement of the available space to determine the size of the greenhouse you can fit.

Making a Selection - Types of Greenhouses
Once you’ve determined the size green house you can accommidate, afford and where you’ll put it, it’s time to consider the type of greenhouse you will build. There are a few options available for hobby green house gardeners.

Once you’ve determined the size green house you can accommidate, afford and where you’ll put it, it’s time to consider the type of greenhouse you will build. There are a few options available for hobby green house gardeners.

The two primary categories green houses fall under are attached and freestanding. Attached type green house includes window-mounted, even-span and lean-to. Attached green house are meant to be attached or housed on a supporting structure like a dedicated wall on your house or building.

Freestanding greenhouses, as the name implies are freestanding structures that do not require a supporting wall or building.

Types of Greenhouses
If you remember from our previous lesson (Introduction - How to Build a Greenhouse), greenhouses fall under two primary categories: Attached and Freestanding.

Attached type green house includes window-mounted, even-span and lean-to. Attached green house are meant to be attached or housed on a supporting structure like a dedicated wall on your house or building. Let’s look at each type of greenhouse in a bit more details.

Attached Greenhouses
There are several types of attached green houses to choose from. Types of attached greenhouses includes Even-Span, Lean-To and Window-Mounted.

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Even-Span Greenhouse
An even-span greenhouse is generally the most costly as well as the largest attached structure available. Even-span greenhouses is generally more capable of holding more plants because of the larger space and can be extended. The shape of the even-span greenhouse offers better air circulation for a more uniform temperature. An even-span greenhouse is capable of holding up to three benches for cultivating crops.

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Lean-To Greenhouse
A lean-to green house is a good choice for gardeners who have limited space. The lean-to green house looks like a greenhouse split in half along the ridge line. Another good reason to select a lean-to green house is that it’s accessible and close to external requirements like electricity and irrigation supply.

Lean-to green houses do have some disadvantages, most notably, the size limitation, available sunlight, controlling temperature and ventilating the structure. It may be difficult to ventilate the lean-to because the supporting structure may absorb excessive heat while the translucent cover allows heat to escape at a rapid rate.

The size of the supporting structure used to hold the lean-to green house in place will determine the size of the greenhouse. The supporting structure also limit the availability of sunlight to one side of the green house. Lean-to greenhouse should be placed in a spot that receives plenty of sunlight. The location of the windows and doors should be planned carefully.

Lastly, you should scrutinize your selected green house location signs of trouble like areas prone to snow or ice sliding from the roof on to the greenhouse, breaking the glass or damaging it in some way.

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Window-Mounted Greenhouse
Window mounted greenhouses are a glass enclosed space that offers the convenience of owning a small hobby green house at a relatively low start-up cost. Window-Mounted greenhouses are a special window that extend outward from your home by about a foot. Window-Mounted green house can hold two to three shelves for growing crops and should be attached on the south or eastside of a structure.

Freestanding Greenhouse
Unlike attached greenhouses, freestanding greenhouse is capable of standing independently. A support structure like a dedicated wall on your home or building is not required to keep a freestanding green house up-right and in place. Freestanding greenhouse offers the benefits of selecting any location to place your greenhouse. Freestanding greenhouses also allow more sunlight to enter the greenhouse because there’s no obstruction on any side. It can be set in an open area to enjoy full sun exposure all day if desired.

Similar to the even-span, freestanding greenhouse is also the lowest cost per sq ft. of growing space. It can accommodate two side benches, two walkways and a center bench and offers acceptable cost-space ratio.

A potential down side is that a separate temperature control system may be required and electricity and irrigation must be installed (if not accessible).

The temperature in larger greenhouses are easier to manage because in smaller greenhouse, the temperature fluctuate rapidly. Exposed areas in smaller greenhouses causes temperature to change frequently. 6 feet wide by 12 feet long for an even-span or freestanding greenhouse is the minimum recommended size.

Greenhouse Structural Materials
Greenhouse can be constructed from several types of materials including aluminum, galvanized steel and wood. There's a wide selection of commercial greenhouse framing materials available. Plastic materials are not the best framing material and often fail to meet the minimum snow and wind load requirements.

Greenhouse Frames
The deciding factor in selecting a greenhouse frame is engineering requirements and personal design ideas. Below are several common greenhouse frames.

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Quonset - Low sidewall height restrict storage space and headroom, however, construction is simple. Electrical conduit or galvanized steel pipe frame

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Gothic - Construction is similar to the Quonset but with a different structural shape and allows more headroom at sidewalls. Wood arches can be used and joined at the ridgeline.

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Rigid-frame - Gable roof and sidewalls allows maximum interior space and air circulation. Requires a soild foundation to support the laterial load on the sidewalls. No columns or trusses to support the roof. Clear-span construction utilizing vertical sidewalls and rafters.
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Post and rafter - Simple construction utilizing embedded post and rafters, requires more structural materials such as wood or metal than other designs. Requires sturdy, deeply embedded posts to tolerate outward rafter forces and wind pressure. Allows more space along sidewalls. Efficient air circulation.
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A-frame - Similar to post and rafter, however, a collar beam joins the upper part of the rafters


Greenhouse Coverings
The type of covering used must correspond with the type of frame used. Different coverings have different lifespan. Film plastic have a 1-3 year lifespan. Other types of coverings includes glass, rigid double-wall plastics and fiberglass.

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Glass - Traditional greenhouse cover material. Inexpensive to maintain. With combined with an aluminum frame, glass is easily maintained with a weather proof structure that minimize heat cost and reatins humidity well. Glass is a flexible cover option as it's suitable of almost any style frame. Tempered glass is two-three times stronger than reqular glass. If using glass, have the manufacturer build the greenhouse as they can be difficult to DIY (Do it Yourself).

Glass is a great option, however, it's start-up cost can be expensive, requires solid frame and foundation to support the heavy glass covering.

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Fiberglass - Lightweight, strong material. Only strong, clear, high-grade fiberglass is recommended because lower grades discolor and reduce light. Tedlar-coated fiberglass may last up to 20 years. A new coat of resin should be applied after 10-15 years to maintain light penetration and prevent dirt and residues from building up on fiberglass.

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Double-wall plastic - Double layer sheets of plastic acrylic or polycarbonate. Long-life, energy-saving rigid covering seperated by webs. Acrylic is long lasting covering that do not yellow easily. Polycarbonate yellows faster than acrylic, however, it's protected by a UV protector coating. Each sheet or layer of plastic will reduce light by up to 10%.

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Film plastic - available in various grade, quality and material. Requires more frequent replacement than other cover options. Low structural cost because it dosen't require a heavy frame. Additionally, plastic film is inexpensive, making start-up cost relatively low compared to the previous options.

Made from polyethylene (PE), polyvinyl chloride (PVC), copolymers and other materials, film plastic offers comparable light penetration to glass.

Although film plastic cost less than other options, they need to be changed more frequent. Utility grade PE will last about a year and has UV inhibitor to protect against UV Rays and last about a year and a half.

PVC or vinly film cost up to 5 times as much as PE, however, they may last up to 5 years. They do, however, attract dirt and needs frequent cleaning.

This article courtesy of www.hydroponicsearch.com


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