This is an old document I found on my computer – originally it was posted on a GeoCities webpage – which no longer is in existence.

History of Greenhouses

Greenhouses have come a long way since the wealthy Europeans and Americans used them to grow oranges and pineapples in glass structures known as orangeries and pineries. These structures became status symbols as well as a practical way to grow fruits, vegetables and exotic plants.

One of the earliest known greenhouses was built around 30 A.D. for the Roman emperor Tiberius. Remember glass had not been invented so the “Specularium” was painstakingly fabricated from tiny translucent sheets of mica. All this was done to satisfy Tiberius’s cravings for cucumbers out of season.

It wasn’t until 1599 that the first practical greenhouse was designed by Jules Charles a French botanist. It was built in (where else) Leiden Holland and used primarily to grow medicinal tropical plants. One of the favorite plants of the day came from the Tamarind (an Indian date) whose fruit was made into a curative drink.

The idea caught on and greenhouses began spreading throughout Europe. The French, who had a love of a new fruit, the orange, began building orangeries to protect the trees from frost. These structures were cumbersome. One structure built by Soloman de Caus in 1619 in Heidelburg which held 340 orange trees. It had a removable roof that had to be painstakingly put up and taken down during the frost season.

Experimenting with angled glass walls and heating flues to improve the efficiency of greenhouses went on throughout the 17th century. New technologies and improved glass led to larger and more elaborate structures that housed plants simply to please the eyes and palates of the European aristocracy.

The palace of Versailles was an example of the elaborate efforts of the royalty to build bigger and more spectacular orangeries. The Versailles orangery was more than 500 feet long, 42 feet wide, and 45 feet high. It had a southern exposure for light and heat.

Despite the elaborateness of these structures, it was the Victorian age in England that ushered in the golden era of the greenhouse. By the end of the mid nineteenth century glass was plentiful and the prohibitive taxes were repealed. The wealthy began competing with each other to build the most elaborate greenhouse, again primarily just to grow citrus fruits and rare flowers. Little thought was given to using the greenhouse for a complete range of food production.

The soaring conservatory at Kew Gardens in England is a prime example of the Victorian greenhouse. There is a replica in San Fransisco’s Golden Gate Park called the Conservatory of Flowers.

In America the first greenhouse on record was built around 1737 by Andrew Faneuil, a wealthy Boston merchant. Like his European predecessors, Faneuil used it primarily to grow fruit. The concept spread slowly, since almost all greenhouses were built for the wealthy. George Washington, perhaps the richest man in America, craved pineapples and ordered a pinery built at Mt. Vernon so he could serve pineapples to his guests.

By 1825, greenhouses were becoming increasingly common. Many of the greenhouses were heated by furnaced- warmed air; some were pit greenhouses built into the earth and heated largely by south facing windows. This is a design that remains highly practical today.

Indeed the modern concept of the greenhouse is simple and practical. No longer is it the private domain of the monied class but something anyone interested in gardening can have for relatively little cost. Today a greenhouse can go virtually anywhere there is space; it can be attached to a house, placed in a backyard or perched on a deck, roof or balcony. In addition greenhouses are becoming more automated, reducing the time and care owners much spend. With new materials available today such as aluminum, pvc piping, fiberglass, acrylic, and polycarbonate panels as well as pressure treated wood ensures the consumer that their greenhouse will stand the test of time. Long gone are the days of shattered glass and overheated/under heated greenhouses.

Getting Started

The world of greenhouses is a magical one, a place where seasons and climates don’t matter. In a greenhouse exotic plants bloom, tropical fruits and fresh vegetables are ready to be picked even in cooler months or if your greenhouse is heated and insulated in the dead of winter. The lure of a greenhouse is powerful. When you walk inside you cut yourself off from the world, you work in the soil and tend to your plants oblivious to the weather outside. You can now grow species you’ve never grown before and try new gardening techniques in a controlled environment.

In the past greenhouses were a luxury, today there are nearly 3 million hobby greenhouses in the U.S. and the number is expected to grow grow grow. The internet has some nice gardening web sites and greenhouse builder’s sites and there are scores of models to choose from; you can research and build your own, use step-by-step plans, buy a kit (you still have to put it together) or have a contractor build one for you. Careful planning will ensure that your new greenhouse is suited to your needs. You must first select an appropriate site where there is plenty of sunlight, then determine what type of greenhouse you want: the size, style, and covering.

Planning Your Greenhouse

You must first assess you needs. How big of a greenhouse do I need? Hobby greenhouse owners suggest making it larger than you anticipate using, because once you start gardening you’ll probably want to expand. In many cases the size of your property will dictate the size of the structure.

Is the purpose of the greenhouse to grow foliage house plants or to grow veggies and flowers. A warm greenhouse that permits maximum light isn’t necessary for foliage house plants. If your like me and use the greenhouse for both, take the sunny location and use shading (shade cloth or a large tree at mid-day will do.

How elaborate of a structure do I need? If you simply want to start your garden early and are not worried about aesthetics you can use the hoop and plastic style. They are easy to assemble and portable, you can move the smaller structures to different parts of the garden as the need arises. Most folks nowadays want something that will look good in their backyards, perhaps complement their deck, gazebo or fence. These types of greenhouse would use a polycarbonate or fiberglass covering and cedar or redwood for the framing and walls. More elaborate glass enclosed structures that have cement foundations, heating and electrical systems are very expensive and not a do-it-yourself project.

Is a building permit necessary? Are there local design ordinances? Must the structure be set back from the property lines? The basic rule of thumb were I live is; if its portable or you can take it apart you don’t need a permit (much like a fence or gazebo). If you start putting running water, heat, electricity and a cement foundation get a permit. Anyway don’t take my word for it ask your local building code people. As for taxes the same applies, if it’s a permanent structure it will be taxed ( i.e. pools).

The cost to maintain a greenhouse and supply it with heat, water and electricity depends on energy costs in you area and what type of greenhouse you build. In most parts of Canada electricity is cheap but its damn cold in the winter. You must build an insulated greenhouse with an energy efficient covering such as Lexan Thermoclear or (dual poly for hoop style) if you want to maintain your greenhouse in the winter. With a small portable 1500 watt heater one could start the season late in March and continue to late October with a 3 season greenhouse without incurring the costs of increased taxes, permits and a more expensive structure. Of course if you live in a warmer climate where it doesn’t freeze cooling would be a concern in summer and you would use the greenhouse to protect your plants from rain and wind. In this case use whatever you can to shade the greenhouse from the midday sun.

Deciding where your going to locate your greenhouse is crucial. Unless it’s a portable model built from a kit it’s there to stay unless your willing to go to a lot of expense and effort to move it. The first consideration is sunlight and it’s important to locate the greenhouse where it will get at least 6 hours of direct sun a day. The preferred exposure is southern, then southeastern, southwestern,eastern, and western. A northern exposure is too shady for a greenhouse. An east-west facing greenhouse will get 25% more light than a north-south as it presents more surface to the sun at a right angle. Take note of any trees, fences or other obstacles that may shut off light for a major portion of daylight hours. Remember that after June 21st the sun starts to get lower on the horizon so that a tree that doesn’t effect the greenhouse in June and July may shade the greenhouse in May or September. Drainage is another key consideration in selecting a site. find a level spot, do not locate it in a depression that will act as a catch basin for rain and snow. Also avoid a boggy area where the soil is always wet. Access to water and electricity is important, the further away the more laborious it is to run the utility lines there. Consider too, the difficulty in walking to your greenhouse in inclement weather.

Greenhouse styles

The style of the greenhouse you select depends on such factors as how permanent you want the structure to be, whether it will be free standing or attached to the house, your building skills, and the type of snow loads in your area. The following are the major styles of greenhouses that can be built; the attached, A-frame, Gothic arch and the span roof (Sun Country Greenhouse).

Attached

Also called a lean-to, this type of greenhouse is an extension of the home. There is usually direct access to the house, water and electricity are easily extended to the structure. In northern climates, an attached greenhouse should not be located under a sloping roof because of icicles and snow slides.

A-Frame

Simple to construct, the A-frame can be built in sections on the ground and then raised into place and covered. Although the shape is ideal for heavy snow loads, it provides limited head room and is difficult to ventilate.

Gothic Arch

The gothic roof line is made from laminated strips over which a permanent covering is installed. Extremely decorative, it is a challenging project, because of the layout and lamination of the arches takes time. This style is a good choice for regions with lots of rain and snow; the curved sides keep precipitation from collecting.

Span Roof

This freestanding style probably has the most typical and usable shape of any greenhouse. The interior layout is extremely practical, and there is easy access for a loaded wheelbarrow through a door at either end. A variation of the span roof design is the gambrel roof (barn shaped) greenhouse, however it is more difficult to build because of all the angles to cut.

Coverings

One of the most important decisions you must make is the choice of material to cover your greenhouse. You will want a material that will let in the maximum amount of light while allowing the least amount of heat to escape. As well it must be strong enough to withstand hail and heavy snow loads. Greenhouse glazing has improved remarkably in recent years. In addition to glass there is a wide range of plastic glazing in the form of film sheeting and rigid panels. You may be confused by the many trade names for each type of plastic. Discuss your options with a reputable greenhouse supplier or builder, and make sure the plastic is for greenhouse.

Glass

The traditional covering for greenhouses, glass is the preferred material for permanence. It lasts indefinitely although it does become brittle with age. Since glass is breakable it is more difficult and dangerous to install, it also requires a much sturdier frame than plastic covered greenhouses. Glass has undergone many improvements in recent years. Among the most important is increased strength (double and triple strength ratings) to resist breaking. Larger panes are also available; because fewer structural members are needed, more light can enter the greenhouse. Frosted and hammered panels can be used break up the light rays for more even distribution. Other advances have cut down on heat loss. Double-walled tempered glass reduces it by about one third. Low-emissivity, or low-e, coating, is another option; it reduces heat loss without a corresponding loss of light. In addition to being energy efficient, low-e glass reduces condensation, partially blocks ultraviolet rays, and makes the inside glass warmer to the touch.

Film Plastic

A greenhouse covered with film plastic is one sixth to one tenth of the cost per square foot of a glass covered structure. Although less permanent than glass, film plastic can be heated as efficiently as glass. Previously, film plastic had a life span of about three months in summer and nine months in winter. Newer, clear types that resist yellowing last three to five years and allow up to 89% light transmission. Sold under many trade names, they are available in many thickness from 2 mil to 15 mil. The thicker the film, the more expensive it is. Weather-resistent polyethylene film plastic, 4 mil thick is perhaps the least expensive film plastic that makes a satisfactory covering for a hobby greenhouse. In choosing plastic film make sure you buy one that has UV protection. You can also buy a plastic film with an infrared inhibitor; it cuts heat loss inside the greenhouse by up to 20% on a cloudless night. Another way to reduce heat loss is to double- layer the plastic creating an air pocket for insulation. This space can be 3/4 to 4 inches thick. Although there is some light transmission loss, heating costs are reduced by one third. Another innovation in film covering is an anticondensate additive that allows moisture buildup to run down the sides of the film instead of onto the plants. By removing the condensation drops that block the sun’s rays, this new type of film plastic allows more light into the greenhouse. In addition, it helps stop disease infection by keeping contaminated moisture from dripping on the plants.

Rigid Plastics

These coverings, which include fiberglass, acrylic, and polycarbonate, come in corrugated and flat forms. Shatterproof, they resist hailstone damage to varying degrees (polycarbonate being the strongest). Some types of rigid plastics get dirty and do not quite let the same amount of light in as glass does. However a good wash with detergent and water to remove dirt or smudges. All rigid plastics retain heat well. For example, fiberglass retains heat 4.4 x more efficiently than glass and 70.8 x more efficient than polyethylene film. Plastic panels have fewer lap joints through which heat can escape. Corrugation in some types makes a very tight fit at lap joints, thus saving heat. The total amount of light transmitted through fiberglass rigid panels is roughly equal to that transmitted through glass. Fiberglass actually has the advantage over glass because it transmits less heat. During the summer a fiberglass covered greenhouse requires less cooling than a glass greenhouse of the same size. Fiberglass with PVC is a durable, relatively lightweight material that resists damage from weather, ultraviolet radiation, and acid rain. Recent improvements in plastics include the introduction of structured sheets. Available in both acrylic and poly carbonate, these are double skinned (for insulation) or corrugated. Acrylic transmits light better but polycarbonate is stronger and more resistant to impact and fire. Both materials can be used on curved areas. When purchasing polycarbonate panels make sure they are UV coated to guard against premature yellowing.

Build or buy a kit?

Once you know what kind of greenhouse you want, you must decide whether to build your own from a plan or assemble a prefabricated model from a kit. Base your decision on such factors as your available time, budget, and building skills. If you want to construct your own but are inexperienced, consider hiring a carpenter to help you. If saving money is your goal, you may be able to do that by building your own, especially if you are able to use scrap materials such as old windows and doors. Even if you buy new materials, you can build a greenhouse for less money than prefab kits. On the other hand if money is not an issue but your skills are then a kit is a logical choice. Kits provide everything you need, including a lightweight foundation for some models. Before deciding on a kit, send away for catalogs and study them carefully. A greenhouse company with an informative web-site can provide more information than a brochure and you will always have a fresh copy on your computer. Make sure assembly instructions are included as well as a list of any materials you may have to buy to outfit the greenhouse such as landscaping cloth, gravel, patio blocks etc.

For some additional information on building a green house, see: http://www.hobby-greenhouse.com/