How to build a domed greenhouse on the site
Content
Greenhouse description
A geodesic or domed greenhouse has the shape of a hemisphere, assembled from triangular elements. The frame can be made of metal, wood or plastic. Of course, a metal structure, especially if treated with anti-corrosion agents, can last longer than other options. The wooden frame is easy to assemble with your own hands, it is environmentally friendly and durable, although it also requires processing with protective equipment for long-term operation. Plastic is light, durable, easy to use, but its service life (especially with year-round use) is unlikely to be longer than that of metal, and its high cost does not give it points either.
For the covering material, take glass, plastic wrap or polycarbonate. Glass is the most transparent material, but it is heavy, fragile, and expensive. The film is often used for a seasonal greenhouse, it is quite transparent, it is easy to work with it. But polycarbonate, with the same transparency and, perhaps, a little more weight, keeps heat much better. High thermal insulation, lack of reaction to changes in air temperature, sufficient transparency, ease of installation made polycarbonate the most demanded cover material for greenhouses, especially those built by hand.
Dome design advantages
It is the dome structure that provides the plants with the greatest amount of light, since it penetrates from all directions. The spherical shape allows you to create the desired microclimate, retains warm air longer without special heating, and allows it to circulate inside the greenhouse.The sun heats the soil in a day, it gives off heat to the air. The air warmed up during the day collects under the dome, cooling down, it descends again. The frame heats up during the day and also gives off heat to the plants. In the center of such a greenhouse, a container with water is installed, which also accumulates heat, it can be used for irrigation.
Dome greenhouses are quite mobile - the segments they are composed of are easy to assemble and disassemble. This design requires much less coating material than others.
The segmented design is earthquake resistant. The round shape provides strength and stability. With year-round use, there is no need to be afraid that the snow will break the roof. And even the strongest wind will not be able to move it or turn it over, therefore, hemispherical greenhouses are most often used in steppe regions, where strong winds can have devastating consequences.
Video "Greenhouse-dome: advantages and features"
This video clearly demonstrates what features a dome-shaped greenhouse structure has.
Flaws
There are not many disadvantages to such a wonderful design. It is necessary to make a rather large greenhouse, more precisely, to take a large diameter of the sphere, so that it is convenient to work inside, straightening up to its full height.In addition, it is most likely problematic to arrange racks for multi-tiered beds. We'll have to be content with one level, and tall plants need to be placed closer to the middle, and low ones around the perimeter.
It is possible to assemble a geodesic greenhouse with your own hands, but it is difficult to independently calculate the dimensions of all elements and build drawings. Not everyone has the opportunity to build frame frames at home. You can, of course, order drawings from specialists, as well as the manufacture of segments, but such a step will significantly increase the cost of the entire product. Perhaps this, along with the forced economy of space, explains why such greenhouses are not very common in our summer cottages.
Another difficulty in assembling a greenhouse with your own hands is that such a large number of joints must be made with a high degree of accuracy in order to ensure the necessary sealing of the building.
If you wish, you can buy a ready-made greenhouse, collect it on the site, grow berries and vegetables in it, or turn it into a winter garden and a greenhouse for exotic flowers.
How to build
If the summer resident nevertheless decides to create a spherical greenhouse with his own hands, he will have to start with calculations, construction of drawings, selection of materials, tools and free time. In addition to metal beams or wooden bars (or maybe plastic profiles) of the required size and material for the planes, you will have to acquire steel strips, self-tapping screws, washers and screws. You will need to purchase foil to close the north side with it from the inside, prepare a tape measure, a level, a shovel.
Dome greenhouse rough draft
Calculation
It is necessary to calculate not only the total area and height of the future greenhouse, but also separately the surface area of the dome itself, the number of ribs and their exact length, intercostal angles, the type and number of connecting elements. All these calculations are based on the desired area, and the height is determined by the diameter. Moreover, it must be remembered that the area of the finished structure will be less than the area of the circle, since the perimeter of the base will be a polygon, not a circle.
There are separate formulas for calculating all these values. But you can avoid this painstaking work with numbers by resorting to the help of a special computer program - a geodetic calculator.
If the summer resident has decided on the desired area and height, then the program will calculate not only the number of segments (triangles), but also their sizes, it will even build a multi-colored drawing that can be guided in making and assembling with your own hands.
The best option for a domed greenhouse with a polycarbonate coating is considered to be a structure where the height is equal to half the diameter of the circle in which the base is inscribed. So with a diameter of 4 m, a dome height of 2 m, the frame will consist of 35 triangles with an edge of 1.23 m or of 30 triangles with an edge of 1.09 m.
Materials (edit)
Knowing the number and size of parts, you can start manufacturing them, paying special attention to accuracy, because the success of the assembly and the degree of sealing of the entire structure depend on it.
The connecting elements are best made of galvanized materials as they are corrosion resistant. If a tree is chosen for the frame, then it is desirable to treat it with a special fire-retardant composition - this will increase its service life.
From steel with a thickness of one and a half to 2 mm, you need to cut strips, drill 7 holes in them at regular intervals for self-tapping screws. Then the strips are bent at an angle of 250 degrees so that on one side there are 3 holes, and on the other - 4. For this work, you will need a bench vice, pliers and a template (so that the angle is the same). The edges of the cut steel strips must be filed.
Site preparation
As for any greenhouse, a flat, unshaded place is chosen for the dome, it is cleaned, and if necessary, leveled.If the foundation is not planned, then the ground (the bottom of the future room) is covered with a protective material, it can be a non-woven fabric that will protect plants from pests and weeds. Before that, it is advisable to remove the sod layer and put it back in an inverted position, that is, with the roots up. A layer of gravel is poured on top - this will be the base of the closed beds.
If you plan to arrange a year-round greenhouse, then a foundation should be made.
If glass is chosen for the dome, then the whole structure will turn out to be very heavy, it is advisable to install it on a foundation or metal piles for stability and prevention of distortions. For the foundation, a trench is pre-dug.
Assembling the frame
To assemble the frame with your own hands means to connect all its segments and fasten it with special connectors. This must be done, guided by the diagram, which was issued by the geodetic calculator.
Quadrangular elements are installed in the base, they are fixed to the ground (or foundation) with metal brackets. Then the triangles are assembled into pentagonal segments.
The whole structure is assembled with your own hands from the bottom up. First, the elements of the lower tier are fixed, then the elements of the next tier are attached to them. It is better to place steel strips on the inside so as not to damage the protective coating, although they are also attached from the outside.
In the upper part of the hemisphere, vents are made; they can be equipped with an automatic opening-closing mechanism for ease of use.
Internal work
It is usually advised to cover the northern part of the dome with foil with your own hands, which will reflect the light, thereby returning it back to the inside of the structure, directing it to the container with water installed in the middle. This container, for example a metal barrel, will heat up during the day, and then give off heat at night.
If the greenhouse will be used in winter, pipes for heating are laid along the walls along the perimeter. When there is little natural air movement, a conventional electrically powered fan can be installed.
Video "Construction of a domed greenhouse-vegetarian"
In this video, the construction developers tell about the features of the construction of a domed greenhouse.