All How to
How to Choose Greenhouse Glazing / Covering Materials


Glazing / Covering: It’s What Makes the Greenhouses

The greenhouse comes “alive” only after its glazing, or cover, is applied. Air temperature, humidity, carbon dioxide level, soil temperature, and light define the greenhouse and plant environment. It must be in balance with the solar radiation entering and the heat leaving through the glazing. The grower then modifies the greenhouse environment to the desired needs of the plants through the use of environmental control systems (heating, ventilation, and cooling) in response to the outdoor environment.


The glazing directly influences the amount (intensity) and the type (diffuse/direct and partial or full spectrum of the sun) of solar energy that reaches the plants inside the greenhouse. The solar energy affects plant growth through plant physiological responses, such as water movement through the plant (for transpiration) and capture of solar energy (for photosynthesis). Solar energy also affects leaf temperature, which is indirectly controlled by the plant through leaf evaporative cooling (evapotranspiration). The plants give off water vapor, which increases the moisture content of the air (humidity) in the greenhouse. This moisture in the air can be removed by ventilation, which exchanges inside air with outside air. Or it may condense on cool surfaces of the greenhouse structure, primarily the glazing.

There is a range of different glazing options for greenhouses and no glazing material is perfect. Each influences the climate within the greenhouse in unique ways. The right glazing for your greenhouse will be determined by your requirements, personal preferences, climate and budget. So, what are the main differences at a glance?

Glass vs. Polycarbonate vs. Plastic / Poly Film