Glass greenhouse construction requirements and performance indicators

With the rapid development of the greenhouse industry, the construction of large-scale multi-storey glass greenhouses has become one of the development trends of modern greenhouses. It has the characteristics of large single-unit greenhouse, high design and construction level, novel management methods, etc. The consumption demand of high, safe and healthy agricultural products played an important role, but its design, installation and construction standards were quite different from other greenhouses. The article combed the main points of the glass greenhouse construction process to readers.

Glass greenhouse construction requirements and performance indicators

Main technical performance indicators

1. Light transmission performance

The higher the light transmittance of the greenhouse, the better its photothermal performance. The light transmittance of the greenhouse is affected by factors such as the light transmittance of the greenhouse cover material and the shadow of the greenhouse. Moreover, the light transmittance of the greenhouse changes with the change of the sun height at different seasons and at different times. Generally, the transmittance of a glass greenhouse is 60% to 70%.

2. Thermal insulation performance

The thermal insulation index of the solar greenhouse envelope layer and the overall thermal insulation performance of the greenhouse are two indicators for measuring the thermal insulation performance of the greenhouse. The indicators for measuring the thermal insulation properties of the overlay are heat transfer coefficient and heat transfer resistance. The unit of heat transfer coefficient is W/(m2·K), and the smaller the value, the better the thermal insulation of the cover layer. The heat transfer resistance is the reciprocal of the heat transfer coefficient, and the unit is (m2·K)/W. The larger the value, the better the insulation of the cover layer. Generally, the heat transfer coefficient of the greenhouse single-layer cover material is above 6.2 W/(m2·K) [heat transfer resistance is below 0.16 (m2·K)/W], and the greenhouse cover can be made by adding insulation curtains indoors. The heat transfer coefficient is reduced to 3~4.8 W/(m2·K) [heat transfer resistance 0.21~0.33 (m2·K)/W]. The overall insulation performance of the greenhouse can be evaluated by the indoor and outdoor temperature difference that is not warmed during the winter night. The temperature difference between indoor and outdoor greenhouses can be maintained at 2~5 °C under single-layer coverage. The indoor and outdoor temperature difference can be increased to 4-8 °C by adding insulation curtains.

3. Greenhouse durability

The factors affecting the durability of the glass greenhouse construction are not only the anti-aging properties of the greenhouse materials, but also the bearing capacity of the greenhouse main structure. The bearing capacity of the main body structure of the greenhouse is directly related to the recurrence time of the upper limit snow load. According to GB/T 51183-2016 "Agricultural Greenhouse Structure Load Specification", the service life of a typical glass greenhouse is about 20 years. It is required to design the upper limit load of wind and snow load for 20 years.