A Detailed Guide to the Latest Greenhouse Construction Techniques

A greenhouse is also called a hothouse, such as a glass greenhouse or a plastic greenhouse. The greenhouse structure should be sealed and insulated, but it should also allow easy ventilation and cooling. Modern greenhouses are equipped with devices that control temperature, humidity, light and other conditions, using computer automation to create the optimal environmental conditions required by plants. Now the editors of Qiannong Network will introduce the construction techniques for greenhouses!

1. Leveling the land and setting out lines: According to the designed solar greenhouse plan, measure and determine the azimuth angle, determine the four corners of the greenhouse, drive stakes at the four corners of the greenhouse, and then determine the positions of the gable walls and the back wall.

2. Building the walls: The soil used for building the earth walls can be taken from the outer side of the greenhouse back wall, or from the soil below the plow layer of the cultivation surface at the front of the greenhouse. If using the soil from the front of the greenhouse, the plow layer (about 25 cm thick) can be dug out and set aside, water the subsoil below, and after one day, dig the subsoil to make the earth wall. First, set up clamping boards according to the thickness of the earth wall, fill in the freshly dug wet soil, and tamp it with a soil tamper or electric tamper, about 20 cm per layer. After tamping one layer, make the second layer, until the required height is reached. The gable walls and the back wall should be built together, not in sections; only in this way can they be solid. If the soil viscosity is not sufficient, wheat straw can be mixed in. In some areas the soil viscosity is very low and the tamping method cannot be used to build walls. In this case, a certain amount of wheat straw can first be mixed into the soil to make mud, then make adobe bricks, and after the adobe bricks dry, build an adobe brick wall. When laying the wall, the gaps between adobe bricks must be tightly filled with straw mud, and both the inside and outside of the wall must be plastered with straw mud. When constructing a brick wall, the foundation must first be tamped solid, and only then can the wall be laid. During construction, the mortar must be full, the brick joints well pointed, and the plastered surface well finished. Both the inside and outside of the wall must be plastered to prevent air leakage. The hollow space between brick wall layers should not be too large or too small. Generally, the width of the hollow is kept between 5-8 cm. The hollow should not be left all the way through; every 3-4 m, bricks should be used to connect the layers, to improve the wall's firmness. The hollow wall can be filled with slag, perlite, or wheat straw as filler, or nothing can be added and only air used for insulation. A hollow wall without filler must be made without cracks. When capping the brick wall, it is best to cap it with mud and chaff for 30 cm, so that the back wall and the rear roof are closely connected, improving insulation performance.

3. Burying the posts and erecting the roof frame: According to the drawings, determine the position of each post and mark it with lime. Dig holes 30-40 cm deep, use stones as post bases to prevent the posts from sinking, and then install the beams on the rear row of posts. The beam head rests on the post, and the beam tail rests on the back wall or on the rear auxiliary posts. Place 3-4 purlins on the beams. The ridge purlin is connected at the beam, forming a straight line, and the other purlins are placed in a staggered manner. To prevent the purlins from sliding down, a small wooden block can be nailed onto the beam below the purlin to block the purlin wood. Some greenhouses use only posts to support the ridge purlin.

4. Covering the rear roof: Cover the purlins or rafters with a layer of waste plastic film, place bundles of corn stalks on the film, with their placement direction perpendicular to the purlins or rafters. Then spread wheat straw or rice straw on the corn stalks, and then lay another layer of plastic film on top, and plaster straw mud on it. The rear roof, made of stalks and wheat straw wrapped in two layers of plastic film, forms a covering like a quilt, and its insulation performance is greatly improved compared with an ordinary rear roof without plastic film. After the rear roof is covered, straw mud should be used to seal the joint between the inner side of the rear roof and the greenhouse back wall.

5. Digging the cold-proof trench: Dig a cold-proof trench 20 cm wide and 40 cm deep along the front edge of the greenhouse.

6. Burying ground anchors and fixing the galvanized wire for the rear roof film-pressing line: Lay a No. 8 galvanized wire equal in length to the greenhouse flat at the bottom of the cold-proof trench, with ground anchors threaded on it. The ground anchors are No. 8 galvanized wire made into ring shapes at both ends. According to the spacing of the arch rods to be buried, every 3 m, tie a brick or wooden stick to the galvanized wire, and place them between these fixing objects. On the outer side of the greenhouse back wall, dig a trench and bury ground anchors in the same way, except that the spacing of the ground anchors can be increased to 2-3 m. After burying, fill in soil and tamp it firm, with the upper ring of the iron anchor exposed above the ground surface. On the rear roof of the greenhouse, stretch a No. 8 galvanized wire, with both ends buried in the ground outside the greenhouse gable walls. When burying, heavy objects should be tied to the ends. Use galvanized wire or nylon rope to fix the galvanized wire, with one end tied to the galvanized wire and the other end tied to the iron anchor buried outside the back wall.

7. Building the front roof: After the post positions are buried, adjust them front and back so that the rows and columns of posts are aligned. Tie 4 m long bamboo strips together in pairs, with the length being appropriate. Insert one end into the cold-proof trench, and press the lower part against the south side of the cold-proof trench with bricks. The angle should make the arch rod vertical to the ground or slightly inclined toward the south when erected. Tie a crossbeam on the posts supporting the front roof. The crossbeam should be 20-30 cm from the top of each row of posts. On the crossbeam, erect small hanging posts. Both the upper and lower ends of the small hanging posts should be drilled, and No. 8 galvanized wire should pass through the holes respectively to bend the arch rods. One end of the small hanging post is tightly tied to the arch rod, and one end is supported on the crossbeam and tied tightly. The upper end of the arch rod can be inserted above the ridge purlin. Then, continuously adjust the small hanging posts so that the height at the same position on the front roof is consistent.

8. Covering the film: The greenhouse film is two or three panels. When using two panels, their widths are 3 m and 5 m respectively; when using three panels, their widths are 2 m, 4 m, and 2 m respectively. First roll back one side of the 3 m or 2 m wide film, bond it with adhesive or iron it with an electric iron into a 5~6 cm wide tube, and insert a nylon rope. The 3 m wide one is fixed at 2.5 m above the ground, and the 2 m wide one is fixed at 1.5 m above the ground. The film is first rolled into a roll, and while covering, it is pulled tight while soil is filled into the cold-proof trench. The nylon rope must be pulled tight and, together with the film, buried underground at the greenhouse gable wall. The upper panel or panels of film are likewise first rolled into a roll, with one end buried underground near the gable wall, and then spread out toward the other end, and after reaching the end, buried underground near the gable wall. There are two ways to fix the end of the film near the rear roof. One is to directly fix it on the ridge purlin with bamboo strips and iron nails; the other method is to fix it on the ridge purlin with bamboo strips and iron nails, then fold it back and fasten it onto the rear roof. The width that can be fastened onto the rear roof is about 0.5-1 m, and the more the better. It is then compacted with straw mud. For a rear roof without added waste film, this method has a relatively good effect on improving insulation performance.

9. Fixing the film-pressing line: After the film is covered, the film-pressing line should be used to press it tight and fix it. The film-pressing line can be commercially available polypropylene greenhouse-specific film-pressing line, or nylon rope or iron wire can be used instead, but it is best not to. Special film-pressing line is best. First tie one end of the film-pressing line to the No. 8 galvanized wire on the greenhouse rear roof, throw it down from the greenhouse, press it on the film between two arch rods, and fasten the lower end to the ground anchor ring, pull it tight and tie it well. The order of fixing the film-pressing lines is sparse first and dense later. First fix a few film-pressing lines at large spacing, then gradually fix one film-pressing line between each arch rod. Both the film-pressing line and the plastic film have a certain elasticity. On the second and third days after fixing the film-pressing lines, tighten them 2-3 more times to ensure they are truly pressed tight. The tightly pressed front roof film appears wavy.

10. Installing straw curtains and paper quilts: The paper quilt is made of 4-6 layers of kraft paper. The straw curtain is made of rice straw or cattail grass. The rice straw curtain is 1.2-1.3 m wide, and the cattail grass curtain is 1.5-1.6 m wide. The length is based on covering the front roof of the greenhouse. In the absence of a paper quilt, two layers of straw curtains can be covered, or the overlap between straw curtains can be increased. Each straw curtain uses two nylon ropes, each about twice the length of the straw curtain or slightly longer, for pulling and releasing. Both ends of each rope are respectively fixed at one edge point at one end of the straw curtain, forming two loops to loop around the straw curtain. The two ropes on the surface of the straw curtain can be pulled to roll up or spread out the straw curtain on the front roof of the greenhouse. The rolled-up straw curtains are placed on the rear roof staggered or one in front of the other. To prevent the straw curtains from sliding down, a stone or two or three bricks can be placed behind each rolled straw curtain as a stop.

11. Handling the entrance and exit: A solar greenhouse can have a door at the east gable wall of the greenhouse. The door should be as small as possible, and an insulation room should be built outside the door. Door curtains should be hung on both the inside and outside of the door. Generally, no door is left at the west gable wall or back wall of the greenhouse.